Antibiotics

10 pages, 855 KB

Open AccessCase Report

Staphylococcal Scalded Skin Syndrome (SSSS) in a Preterm Infant: Clinical Presentation and Role of Next-Generation Sequencing in Toxin Gene Identification—A Case Report

by Giovanni Lorenzin, Maddalena Carlin, Claudio Scarparo, Mariachiara Cardellini, Francesca Tota and Aldo Naselli

Antibiotics 2025, 14(10), 1017; https://doi.org/10.3390/antibiotics14101017 - 13 Oct 2025

Abstract

Staphylococcal scalded skin syndrome (SSSS) is a rare, toxin-mediated dermatosis caused by exfoliative toxin–producing Staphylococcus aureus strains, with neonates and preterm infants being particularly vulnerable due to immature immunity and reduced toxin clearance. We report the case of a male preterm infant, born [...] Read more.

Staphylococcal scalded skin syndrome (SSSS) is a rare, toxin-mediated dermatosis caused by exfoliative toxin–producing Staphylococcus aureus strains, with neonates and preterm infants being particularly vulnerable due to immature immunity and reduced toxin clearance. We report the case of a male preterm infant, born at 24 weeks of gestation, who presented at the age of one month with fever and later developed widespread erythema, flaccid bullae, and periorificial desquamation. Methicillin-sensitive S. aureus (MSSA) was isolated from blood, catheter, and auricular swabs. Whole-genome sequencing revealed sequence type ST121 carrying both eta and etb genes, confirming the dual-toxin profile associated with severe disease. The infant improved with targeted intravenous oxacillin following catheter removal. A subsequent nasal swab identified a methicillin-resistant S. aureus (MRSA) ST30 strain lacking exfoliative toxins, consistent with asymptomatic colonization. This case underscores the importance of integrating advanced molecular diagnostics such as next-generation sequencing into the management of neonatal SSSS, enabling precise identification of virulence factors and resistance genes. Literature also highlights the global epidemiology of SSSS, diversity of S. aureus toxin genes, and value of genomic surveillance in neonatal care; our case aligns with reports of ST121 strains carrying both ETA and ETB, where the dual-toxin profile drives rapid onset, extensive skin disease, and good outcomes with prompt therapy. Full article

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16 pages, 2952 KB

Open AccessArticle

Influence of Florfenicol Treatments on Marine-Sediment Microbiomes: A Metagenomic Study of Bacterial Communities in Proximity to Salmon Aquaculture in Southern Chile

by Sergio Lynch, Pamela Thomson, Rodrigo Santibañez and Ruben Avendaño-Herrera

Antibiotics 2025, 14(10), 1016; https://doi.org/10.3390/antibiotics14101016 - 13 Oct 2025

Abstract

Background/Objectives: Metagenomic analyses are an important tool for understanding ecological effects, particularly in sites exposed to antimicrobial treatments. Marine sediments host diverse microbial communities and may serve as reservoirs for microbial resistance. Although it is known that antimicrobials can alter microbial composition, [...] Read more.

Background/Objectives: Metagenomic analyses are an important tool for understanding ecological effects, particularly in sites exposed to antimicrobial treatments. Marine sediments host diverse microbial communities and may serve as reservoirs for microbial resistance. Although it is known that antimicrobials can alter microbial composition, specific impacts on sediments surrounding salmon farms remain poorly understood. This study analyzed bacterial community structure in marine sediments subjected to florfenicol treatment from salmon farms in the Los Lagos Region of southern Chile. Methods: Sediment samples were collected and examined through DNA extraction and PCR amplification of the 16S rRNA gene (V3-V4 region). Sequences were analyzed using a bioinformatics pipeline, and amplicon sequence variants (ASVs) were taxonomically classified with a Naïve Bayesian classifier. The resulting ASV abundance were then used to predict metabolic functions and pathways via PICRUSt2, referencing the MetaCyc database. Results: Significant differences in bacterial phyla were observed between the control farm and two farms treated with florfenicol (17 mg kg⁻¹ body weight per day) for 33 and 20 days, respectively. Farm 1 showed notable differences in phyla such as Bacteroidota, Bdellovibrionota, Crenarchaeota, Deferrisomatota, Desulfobacterota, Fibrobacterota, Firmicutes, and Fusobacteriota, while Farm 2 exhibited differences in the phyla Bdellovibrionota, Calditrichota, Crenarchaeota, Deferrisomatota, Desulfobacterota, Fusobacteriota, Nanoarchaeota, and Nitrospirota. Shannon Index analysis revealed a reduction in alpha diversity in the treated farms. Comparative analysis between the control and the treated farms showed pronounced shifts in the relative abundance of several bacterial phyla, including statistically significant differences in Chloroflexi and Firmicutes. Predicted functional pathways revealed a notable enrichment of L-methionine biosynthesis III in Farm 2, suggesting a shift in sulfur metabolism potentially driven by antimicrobial treatment. Additionally, increased activity in fatty acid oxidation pathways indicates a higher microbial potential for lipid degradation at this site. Conclusions: These findings highlight the considerable influence of florfenicol on sediment microbial communities and reinforce the need for sustainable management strategies to minimize ecological disruption and the spread of antimicrobial resistance. Full article

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11 pages, 894 KB

Open AccessArticle

Multidrug-Resistant Staphylococcus haemolyticus ST42 Carrying ΨSCCmec₅₇₃₉₅-like SCCmec and Resistant Islands with Type I aj1–LP–fusB Structure Emerges in Taiwan Hospitals

by Cheng-Mao Ho, Lee-Chung Lin, Yu-Hsiang Ou, Kai-Hsiang Lin and Jang-Jih Lu

Antibiotics 2025, 14(10), 1015; https://doi.org/10.3390/antibiotics14101015 - 13 Oct 2025

Abstract

Background/Objectives: Staphylococcus haemolyticus is a common commensal bacterium that has emerged as an important nosocomial pathogen. Its multi-antibiotics resistance presents substantial therapeutic challenges in healthcare settings worldwide. Despite its growing clinical relevance, most investigations into antimicrobial resistance determinants have been focused on [...] Read more.

Background/Objectives: Staphylococcus haemolyticus is a common commensal bacterium that has emerged as an important nosocomial pathogen. Its multi-antibiotics resistance presents substantial therapeutic challenges in healthcare settings worldwide. Despite its growing clinical relevance, most investigations into antimicrobial resistance determinants have been focused on Staphylococcus aureus or Staphylococcus epidermidis, leaving S. haemolyticus comparatively understudied. This study aimed to elucidate the genetic basis of multi-drug resistance by characterizing mobile genetic elements associated with predominant S. haemolyticus clones circulating in Taiwan. Methods: From 2010 to 2017, 140 clinical targeted isolates of S. haemolyticus were obtained from individual patients. Two representative strains, SH53 (ST3) and SH51 (ST42), were sequenced using the PacBio^TM platform. The structural organization of SCCmec cassettes and phage-associated resistance islands in the remaining 138 isolates was analyzed by polymerase chain reaction (PCR) using specifically designed primers. Results: Of the 140 isolates, 92 (65.7%) were ST42 and 48 (34.3%) were ST3. PCR analysis showed that over two-thirds harbored heavy metal resistance genes. cadD, cadX, arsC, arsB, and arsR occurred in 90.2% of ST42 isolates, with copA in 71.7%. In ST3, these five genes were present in 89.6%, and copA in 64.6%. Fusidic acid (FA) resistance was more frequent in ST42 (46.7%) than ST3 (22.9%) (p = 0.015). Only one ST42 isolate carried fusC. The remaining 52 FA-resistant isolates contained a type I aj1–leader peptide (LP)–fusB structure downstream of smpB, except for a single ST42 isolate with the type IV structure. Conclusions: MDR ST42 S. haemolyticus carrying SCCmec cassettes with heavy metal resistance genes and phage-related islands carrying type I aj1–leader peptide (LP)–fusB structures may represent emerging opportunistic pathogens in Taiwan. Continued longitudinal surveillance is warranted to track the evolution of resistance-associated mobile elements under selective antimicrobial pressure. Full article

(This article belongs to the Section Mechanism and Evolution of Antibiotic Resistance)

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22 pages, 4616 KB

Open AccessArticle

Isolation of Dual-Active Drugs with Anticancer and Antibacterial Activities That Target Both Tubulin and FtsZ

by Yanting Wang, Xufang Wang, Chunmeng Yao, Yaliang Zhang, Lantian Liu, Yan Cao and Bin Lu

Antibiotics 2025, 14(10), 1014; https://doi.org/10.3390/antibiotics14101014 - 13 Oct 2025

Abstract

Background: Cancer patients experience a high incidence of concomitant infections due to the effects of chemotherapy drugs and their suppressed immune function. Infection has become a major cause and an accelerating factor of cancer-related deaths. The combined use of anticancer drugs and [...] Read more.

Background: Cancer patients experience a high incidence of concomitant infections due to the effects of chemotherapy drugs and their suppressed immune function. Infection has become a major cause and an accelerating factor of cancer-related deaths. The combined use of anticancer drugs and antibiotics can produce adverse effects, necessitating the urgent search for dual-active drugs that are effective against both cancer and bacteria. Since tubulin has a homologous protein filamenting temperature-sensitive mutant Z (FtsZ) in bacteria, tubulin inhibitors have the potential to emerge as dual-active drugs against both cancer and bacteria. Methods: A comprehensive screening of a tubulin inhibitor library, encompassing 196 compounds, was conducted to evaluate their various activities. Results: Compounds 6, 23, 33, 56, 60, and 71 exhibited both anticancer and antibacterial activities in vitro, and 23, 33, 56, and 60 displayed varying degrees of FtsZ inhibitory activity. Particularly, compound 23 stood out as the most potent, exhibiting not only the strongest anticancer activity with IC₅₀ values of 12, 20, and 10 nM against A549, MCF-7 and Hela cells, respectively, but also the most exceptional antibacterial activity with minimum inhibitory concentration (MIC) values of 8, 8, 64, and 32 μM against Staphylococcus aureus (S. aureus), Bacillus subtilis (B. subtilis), Escherichia coli (E. coli), and Pseudomonas aeruginosa (P. aeruginosa), respectively. Furthermore, compound 23 possessed the superior FtsZ inhibitory activity, facilitating polymerization. This was evident in the remarkably elongated cell morphology of Bacillus subtilis treated with compound 23. To gain a deeper understanding of the underlying mechanisms, molecular docking studies were conducted, revealing the interaction mode between compound 23 and both tubulin and FtsZ, further elucidating its multifaceted biological activities. Conclusions: The dual-active drugs obtained in this study provide a new solution to the problem of bacterial infection in cancer patients. The revealed FtsZ as the antibacterial target provides an important theoretical basis for further optimization of such drugs. Full article

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22 pages, 1164 KB

Open AccessArticle

Prevalence, Risk Factors, and Endoscopic Findings of Helicobacter pylori Infection Among Lebanese Patients Undergoing Gastroscopy: A Retrospective Study from a Single Tertiary Center

by Rim Boutari, Nadeen Zayour, Ali Naji Hmedeh, Diana Khaled Bashashi, Fatima Assaf, Jana Al Tahan, Nancy Zrara, Nour Al-Mokdad, Omar Al Khatib, Abbas Zreik, Laura Akiki, Bilal Hoteit, Maha Hoteit, Zahra Sadek, Nikolaos Tzenios and Mahmoud Hallal

Antibiotics 2025, 14(10), 1013; https://doi.org/10.3390/antibiotics14101013 - 11 Oct 2025

Abstract

(1) Background: Gastric cancer continues to pose a significant public health challenge, with its incidence influenced by various factors, including Helicobacter pylori (H. pylori) infection. In Lebanon, data on H. pylori prevalence and its associated risk factors remain limited. This study [...] Read more.

(1) Background: Gastric cancer continues to pose a significant public health challenge, with its incidence influenced by various factors, including Helicobacter pylori (H. pylori) infection. In Lebanon, data on H. pylori prevalence and its associated risk factors remain limited. This study aimed to determine the prevalence of H. pylori infection among Lebanese outpatients presenting with gastrointestinal symptoms undergoing gastroscopy, to explore correlations between the infection and demographic and clinical variables, and to evaluate the prevalence of associated conditions such as gastritis, duodenitis, and intestinal metaplasia. (2) Methods: Using a retrospective design, data from 786 patients admitted at a hospital in Beirut over a three-year period were extracted from records. (3) Results: The prevalence of H. pylori infection was 29.6% despite 91.5% of patients showing signs of gastritis on endoscopy. The infection showed significant associations with erosive gastritis, non-erosive gastritis, mosaic gastritis, as well as with both erosive and non-erosive duodenitis. No significant relationships were observed between H. pylori and demographic factors, atrophic, or nodular gastritis. (4) Conclusions: These findings underscore the importance of targeted testing and early eradication of H. pylori to manage gastritis effectively and reduce the risk of progression to more serious gastric conditions in the Lebanese population. Full article

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11 pages, 1013 KB

Open AccessArticle

Impact of Complying with a Procalcitonin-Guided Stopping Rule on the Duration of Antibiotic Therapy in Critically Ill Patients: A Real-Life Study

by Edwige Péju, Auguste Dargent, Jean-Baptiste Roudaut, Sébastien Prin, Pascal Andreu, Audrey Large, Jean-Pierre Quenot and Pierre-Emmanuel Charles

Antibiotics 2025, 14(10), 1012; https://doi.org/10.3390/antibiotics14101012 - 11 Oct 2025

Abstract

Background: Reducing critically ill patients’ exposure to antibiotics is mandatory. In randomized controlled trials, procalcitonin (PCT)-guided algorithms (i.e., antibiotic therapy [ABT] should be stopped whenever PCT is less than 0.5 µg/L or is below 80% of the peak value) reduced the duration of [...] Read more.

Background: Reducing critically ill patients’ exposure to antibiotics is mandatory. In randomized controlled trials, procalcitonin (PCT)-guided algorithms (i.e., antibiotic therapy [ABT] should be stopped whenever PCT is less than 0.5 µg/L or is below 80% of the peak value) reduced the duration of (ABT) more than compliance with the current guidelines. However, the interest of such stopping rules in daily practice remains debated. Thus, we carried out a real-life study addressing this issue. Results: During the study period, 112 patients with sepsis upon intensive care unit admittance were included. The median age was 66 years (56–79). Half of the patients presented with acute respiratory failure. Pneumonia was diagnosed in 78% of them, and 41% met septic shock criteria. The initial ABT was empirical in most cases, and appropriateness rate to the isolated bacteria reached 71%. A median number of four PCT measurements was achieved in both groups. The compliance rate with the PCT algorithm was 54%. The median duration of ABT was 5 (4–7) days if the PCT algorithm was followed, as compared to 7 (5–10) days otherwise (p < 0.001). This ABT stopping rule allowed a 2-day reduction in the treatment duration as compared with those recommended by the guidelines (p < 0.001). The only independent factor associated with shorter treatment duration was compliance with the PCT algorithm (OR = 0.74, 95% CI [0.62; 0.88]; p < 0.001). Regarding safety, no difference in outcome was found between the two groups. Conclusions: Complying with one PCT-based stopping rule is associated with a significant reduction in the duration of ABT in septic critically ill patients, without apparent impact on patient outcomes. Full article

(This article belongs to the Special Issue Infection Diagnostics and Antimicrobial Therapy for Critical Patient)

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21 pages, 654 KB

Open AccessArticle

Establishing Priority Pediatric Antimicrobial Stewardship Interventions in the US: Findings from a Delphi Consensus Study

by Harry Obeng, Emmanuel Tetteh, Sara Malone, Lauren Walsh, Tyler Walsh, Fernando J. Bula-Rudas, Ritu Banerjee, Adam W. Brothers, Joshua C. Herigon, Katie Namtu, Scott Weissman, Daniel Riggsbee, Jared Olson, Debra Lynn Palazzi, Ann Wirtz, Matthew Sattler, Jessica Tansmore, Brittany A. Rodriguez, Monica Abdelnour, Joshua R. Watson, Alison C. Tribble, Jessica Gillon, Mari Nakamura, Sarah Jones, Jason G. Newland and Virginia R. McKay Show full author list Hide full author list

Antibiotics 2025, 14(10), 1011; https://doi.org/10.3390/antibiotics14101011 - 11 Oct 2025

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Abstract

Background/Objectives: Antimicrobial resistance (AMR) is a major global health threat, with children at higher risk due to developmental differences in drug metabolism, limited treatment options and inappropriate antibiotic use. Pediatric antimicrobial stewardship programs (ASPs) face implementation challenges, often relying on adult-based guidelines and [...] Read more.

Background/Objectives: Antimicrobial resistance (AMR) is a major global health threat, with children at higher risk due to developmental differences in drug metabolism, limited treatment options and inappropriate antibiotic use. Pediatric antimicrobial stewardship programs (ASPs) face implementation challenges, often relying on adult-based guidelines and limited pediatric-specific evidence. This study aimed to identify and prioritize the most critical areas for pediatric ASP intervention development through a structured, multi-round Delphi consensus process with experts in antimicrobial stewardship and infectious diseases. Method: A four-round modified Delphi process was conducted to identify and prioritize key pediatric ASP interventions. Experts in antimicrobial stewardship and infectious diseases were recruited through an existing clinical trial. Using an iterative survey and in-person discussions, experts provided input on priority areas, which were thematically grouped and refined across rounds. Structured feedback supported real-time refinement and consensus-building. Results: Twenty experts participated in the process, generating 25 priority items in Round 1 through open-ended responses. These were narrowed to seven key priorities through structured voting and discussion. The final items were clustered into three intersecting themes: Care Settings, Prescriptions, and Strategies. Care Settings focused on high-impact areas such as outpatient clinics and intensive care units, where misuse is common and/or care is complex. The prescriptions theme prioritized shorter durations and narrow-spectrum agents. The strategy theme highlighted the need for outcome-based metrics, improved diagnostic stewardship, and routine tracking of patient outcomes to guide and assess stewardship efforts. Conclusions: This expert consensus identified key priorities for pediatric ASPs, providing a foundation for future interventions. Findings can be used to inform policy and practice, improving the appropriate use of antimicrobials in pediatrics and combating AMR. Full article

(This article belongs to the Special Issue Antimicrobial Stewardship—from Projects to Standard of Care)

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13 pages, 1564 KB

Open AccessArticle

Impact of Light-Activated Nanocomposite with Erythrosine B on agr Quorum Sensing System in Staphylococcus aureus

by Larysa Bugyna, Ľubomír Švantner, Katarína Bilská, Marek Pribus and Helena Bujdáková

Antibiotics 2025, 14(10), 1010; https://doi.org/10.3390/antibiotics14101010 - 11 Oct 2025

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Abstract

Backround: The agr (accessory gene regulator) quorum sensing (QS) system of Staphylococcus aureus participates significantly in its virulence and biofilm formation—either through its activation or suppression. The aim of this study was to investigate the impact of photoactive nanomaterials that have been functionalized [...] Read more.

Backround: The agr (accessory gene regulator) quorum sensing (QS) system of Staphylococcus aureus participates significantly in its virulence and biofilm formation—either through its activation or suppression. The aim of this study was to investigate the impact of photoactive nanomaterials that have been functionalized with erythrosine B (EryB) on the modulation of this agr QS system on three methicillin-resistant S. aureus (MRSA). Methods: The functionality of the agr system was determined by the CAMP test and by quantitative PCR (qPCR) to analyze the expression of the hld gene, which is located within the RNAIII and encodes δ-hemolysin. The biofilm was evaluated by crystal violet assay and fluorescence microscopy. The anti-biofilm activity was determined by calculating the colony-forming units. The relative expression of the hld gene, determined by qPCR. Results: Using the CAMP test, S66 and S68 strains were found to be agr-positive, and strain S73 was agr-negative. The relative expression of the hld gene increased only in the agr-positive strains (600- and 1000-fold). In these strains, the biofilm was less compact compared to the dense biofilm formed by the agr-negative strain. The anti-biofilm effectiveness on the nanocomposite with EryB after irradiation reduced the growth of biofilm cells by 100- to 1000-fold compared to the biofilm on polyurethane alone. The qPCR results showed a significant decrease in the relative expression of the hld gene in the agr-positive strains after irradiation compared to the non-irradiated samples. Conclusions: These results suggest that photoactive nanocomposites with EryB can significantly reduce biofilm formed by MRSA strains, regardless of the functionality of the agr QS system. Full article

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38 pages, 2717 KB

Open AccessArticle

The Potential for Sample Testing at the Pen Level to Inform Prudent Antimicrobial Selection for Bovine Respiratory Disease Treatment: Investigations Using a Feedlot Simulation Tool

by Dana E. Ramsay, Wade McDonald, Sheryl P. Gow, Lianne McLeod, Simon J. G. Otto, Nathaniel D. Osgood and Cheryl L. Waldner

Antibiotics 2025, 14(10), 1009; https://doi.org/10.3390/antibiotics14101009 - 11 Oct 2025

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Abstract

Background: Antimicrobial drugs are used to treat bacterial diseases in livestock production systems, including bovine respiratory disease (BRD) in feedlot cattle. It is recommended that therapeutic antimicrobial use (AMU) in food animals be informed by diagnostic tests to limit the emergence of antimicrobial [...] Read more.

Background: Antimicrobial drugs are used to treat bacterial diseases in livestock production systems, including bovine respiratory disease (BRD) in feedlot cattle. It is recommended that therapeutic antimicrobial use (AMU) in food animals be informed by diagnostic tests to limit the emergence of antimicrobial resistance (AMR) and preserve the effectiveness of available drugs. Recent evidence demonstrates preliminary support for the pen as a prospective target for AMR testing-based interventions in higher-risk cattle. Methods: A previously reported agent-based model (ABM) was modified and then used in this study to investigate the potential for different pen-level sampling and laboratory testing-informed BRD treatment strategies to favorably impact selected antimicrobial stewardship and management outcomes in the western Canadian context. The incorporation of sample testing to guide treatment choice was hypothesized to reduce BRD relapses, subsequent AMU treatments and resultant AMR in sentinel pathogen Mannheimia haemolytica. The ABM was extended to include a discrete event simulation (DES) workflow that models the testing process, including the time at sample collection (0 or 13 days on feed) and the type of AMR diagnostic test (antimicrobial susceptibility testing or long-read metagenomic sequencing). Candidate testing scenarios were simulated for both a test-only control and testing-informed treatment (TI) setting (n = 52 total experiments). Key model outputs were generated for both the pen and feedlot levels and extracted to data repositories. Results: There was no effect of the TI strategy on the stewardship or economic outcomes of interest under baseline ecological and treatment conditions. Changes in the type and number of uses by antimicrobial class were observed when baseline AMR in M. haemolytica was assumed to be higher at feedlot arrival, but there was no corresponding impact on subsequent resistance or morbidity measures. The impacts of sample timing and diagnostic test accuracy on AMR test positivity and other outputs were subsequently explored with a theoretical “extreme” BRD treatment protocol that maximized selection pressure for AMR. Conclusions: The successful implementation of a pen-level sampling and diagnostic strategy would be critically dependent on many interrelated factors, including the BRD treatment protocol, the prevalences of resistance to the treatment classes, the accuracy of available AMR diagnostic tests, and the selected “treatment change” thresholds. This study demonstrates how the hybrid ABM-DES model can be used for future experimentation with interventions proposed to limit AMR risk in the context of BRD management. Full article

(This article belongs to the Special Issue Veterinary Antibiotics in Food-Producing Animals: Residue Detection, Risk Assessment and Regulatory Advances)

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13 pages, 1371 KB

Open AccessArticle

Cerebrospinal Pharmacokinetic Modeling and Pharmacodynamic Simulation of High-Dose Cefazolin for Meningitis Caused by Methicillin-Susceptible Staphylococcus aureus

by Tetsushu Onita, Kazuro Ikawa, Noriyuki Ishihara, Hiroki Tamaki and Takahisa Yano

Antibiotics 2025, 14(10), 1008; https://doi.org/10.3390/antibiotics14101008 - 11 Oct 2025

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Abstract

Background: Cefazolin is being increasingly used to treat central nervous system infections caused by methicillin-susceptible Staphylococcus aureus (MSSA) to mitigate the side effects of existing anti-Staphylococcal drugs. This study aims to develop a cerebrospinal pharmacokinetic (PK) model to predict the cefazolin concentration in [...] Read more.

Background: Cefazolin is being increasingly used to treat central nervous system infections caused by methicillin-susceptible Staphylococcus aureus (MSSA) to mitigate the side effects of existing anti-Staphylococcal drugs. This study aims to develop a cerebrospinal pharmacokinetic (PK) model to predict the cefazolin concentration in cerebrospinal fluid (CSF) and to individualize the dosing regimen for MSSA meningitis. Methods: A cerebrospinal PK model was developed based on the existing literature and used to estimate the probability of attaining PK/ pharmacodynamic (PD) targets. These targets were set as 100% time above the minimum inhibitory concentration (T > MIC) in CSF. The cerebrospinal PK/PD breakpoint was defined as the highest MIC at which target attainment probability in CSF was ≥90%. The mean CSF/serum ratio estimated from the literature was 0.0525 after a dose of 1–3 g (sampling time: 1–9 h after dose) in adult patients with suspected meningitis. This ratio was incorporated into this PK model based on a hybrid approach. Results: For patients with creatinine clearance (CL_cr) = 90 mL/min, the cerebrospinal PK/PD breakpoint MICs of continuous infusion regimens (6–12 g/day) reached 0.5 µg/mL, which can inhibit the growth of 90% of the MSSA population (MIC₉₀). Furthermore, for patients with renal dysfunction (CL_cr = 30 mL/min), a dose reduction (4 g/day) may be required to avoid excessive drug exposure. Conclusions: High-dose continuous infusion of cefazolin may be appropriate for MSSA meningitis in patients with normal renal function, while dose adjustments are needed for those with renal impairment. Full article

(This article belongs to the Special Issue Pharmacokinetics and Pharmacodynamics of Antibacterial and Antivirulence Drugs, 2nd Edition)

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7 pages, 239 KB

Open AccessCase Report

Imipenem/Relebactam Plus Aztreonam: First Reported Use in MDR Klebsiella pneumoniae Sternal Infection Complicated by Bacteremia

by Luca Pipitò, Raffaella Rubino, Rita Immordino, Eleonora Bono, Teresa Fasciana, Celestino Bonura, Giovanni Maurizio Giammanco, Vincenzo Argano and Antonio Cascio

Antibiotics 2025, 14(10), 1007; https://doi.org/10.3390/antibiotics14101007 - 10 Oct 2025

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Abstract

Background: Carbapenem-resistant Klebsiella pneumoniae (CRKP) poses a significant therapeutic challenge, particularly when multiple resistance mechanisms, such as metallo-β-lactamases (MBLs) and Klebsiella pneumoniae carbapenemase (KPC), coexist. Case description: We describe a case of a 51-year-old male with a post-sternotomy surgical site infection and concurrent [...] Read more.

Background: Carbapenem-resistant Klebsiella pneumoniae (CRKP) poses a significant therapeutic challenge, particularly when multiple resistance mechanisms, such as metallo-β-lactamases (MBLs) and Klebsiella pneumoniae carbapenemase (KPC), coexist. Case description: We describe a case of a 51-year-old male with a post-sternotomy surgical site infection and concurrent bacteremia caused by a CRKP. Sternal swab and mediastinal liquid culture results highlighted CRKP harboring bla_NDM and bla_KPC genes, while the blood isolate showed bla_CTX and bla_KPC, indicating phenotypic resistance to ceftazidime-avibactam. All the strains exhibited phenotypic susceptibility to meropenem-vaborbactam (MEV), despite having a high minimum inhibitory concentration. Following clinical failure of MEV-based therapy, combination treatment with aztreonam (ATM) and imipenem/cilastatin/relebactam (IMI/REL), plus gentamicin, was initiated. Therapy was well tolerated and resulted in microbiological eradication and full clinical recovery. The patient completed 49 days of ATM and IMI/REL without relapse over a 3-month follow-up period. This is, to the best of our knowledge, the first reported case of IMI/REL being used in combination with ATM. Full article

(This article belongs to the Special Issue Innovative Treatments for Hospital-Acquired Multidrug-Resistant Bacterial Infections)

18 pages, 1656 KB

Open AccessArticle

Impact of Antimicrobial-Resistant Bacterial Pneumonia on In-Hospital Mortality and Length of Hospital Stay: A Retrospective Cohort Study in Spain

by Iván Oterino-Moreira, Montserrat Pérez-Encinas, Francisco J. Candel-González and Susana Lorenzo-Martínez

Antibiotics 2025, 14(10), 1006; https://doi.org/10.3390/antibiotics14101006 - 10 Oct 2025

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Abstract

Objectives: Antimicrobial resistance is a major global health threat. This study aimed to assess the impact of antimicrobial-resistant bacterial pneumonia on in-hospital mortality and length of hospital stay in Spain using a large, nationally representative cohort. Methods: A retrospective cohort study that used [...] Read more.

Objectives: Antimicrobial resistance is a major global health threat. This study aimed to assess the impact of antimicrobial-resistant bacterial pneumonia on in-hospital mortality and length of hospital stay in Spain using a large, nationally representative cohort. Methods: A retrospective cohort study that used data from Spain’s Registry of Specialized Health Care Activity (RAE-CMBD) between 2017 and 2022. Hospitalized adults with bacterial pneumonia were included. Hospitalization episodes with bacterial antimicrobial resistance, defined according to ICD-10-CM codes for antimicrobial resistance (Z16.1, Z16.2), were analyzed versus hospitalization episodes without these codes. Multivariate logistic regression models, adjusted for potential confounders (e.g., age, comorbidity, intensive care unit admission) and sensitivity analyses (Poisson regression and propensity score matching test), were performed. Results: Of the 116,901 eligible hospitalizations, 6017 (5.15%) involved antimicrobial-resistant bacteria. Patients with antimicrobial-resistant bacterial pneumonia were older (median 75 vs. 72 years), had greater comorbidity (Elixhauser–van Walraven index: 8 vs. 5), and were more frequently admitted to the intensive care unit (22% vs. 14%). Crude in-hospital mortality was higher in the antimicrobial resistance group (18.46% vs. 10.05%, p < 0.0001), with an adjusted odds ratio of 1.47 (95% confidence interval, 1.36–1.58), p < 0.0001. Length of hospital stay was prolonged in antimicrobial resistance patients (median 14 vs. 8 days; adjusted incident rate ratio of 1.46; 95% confidence interval of 1.41 to 1.50). The most prevalent antimicrobial resistant pathogens were Staphylococcus aureus and Gram-negative bacilli (Pseudomonas aeruginosa, Klebsiella pneumoniae, and Escherichia coli). Conclusions: Antimicrobial resistance is associated with longer hospital stays and an up to 50% higher risk of mortality. Despite the implementation of control policies in place over the past decade, policymakers must strengthen AMR surveillance and ensure adequate resource allocation. Clinicians, in turn, must reinforce antimicrobial stewardship and incorporate rapid diagnostic tools to minimize the impact of antimicrobial resistance on patient outcomes. Full article

(This article belongs to the Section Mechanism and Evolution of Antibiotic Resistance)

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19 pages, 3693 KB

Open AccessArticle

Genomic Insights into an Environmental Vibrio parahaemolyticus Biofilm Isolate: Deciphering Alternative Resistance Mechanisms and Mobilizable Genetic Elements

by Huiyu Liu, Yujian Dong, Zhongyang Lin and Olivier Habimana

Antibiotics 2025, 14(10), 1005; https://doi.org/10.3390/antibiotics14101005 - 10 Oct 2025

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Abstract

Background/Objectives: Biofilms are key in spreading antibiotic resistance in various ecosystems. This study employed comparative genomics to examine the resistance and adaptability mechanisms of the Vibrio parahaemolyticus strain Vaw-5, isolated from a seafood market biofilm. Methods: A comparative examination of Vaw-5 and 32 [...] Read more.

Background/Objectives: Biofilms are key in spreading antibiotic resistance in various ecosystems. This study employed comparative genomics to examine the resistance and adaptability mechanisms of the Vibrio parahaemolyticus strain Vaw-5, isolated from a seafood market biofilm. Methods: A comparative examination of Vaw-5 and 32 publicly available V. parahaemolyticus genomes identified a distinct set of genetic resistance characteristics. Results: Unlike clinical strains, Vaw-5 lacks acquired antimicrobial resistance genes like the blaCARB and qnr variations. Instead, its resistance potential is based on chromosomal alterations, efflux pump systems (vmeAB, vcmD), and a unique repertoire of 16 strain-specific transposons, including Tn5501 and Tn5393, which are well-known vectors for antibiotic resistance gene (ARG) mobilization. Although not multidrug-resistant, Vaw-5 possesses unique genomic islands that share negligible homology with those of clinical strains, enriched with gene clusters for environmental adaptation, such as exopolysaccharide production and a fully functional Type VI Secretion System. Vaw-5 carries a distinctive plasmid with the resistance gene aac(2 $^{'}$ )-Ia. Conclusions: Biofilm adaptation promotes structural integrity, inherent processes, and resistance above standard ARG acquisition. This study focuses on how biofilm communities in the food chain can operate as covert incubators for mobilizable resistance determinants, emphasizing the significance of ecological monitoring within a One Health paradigm to reduce possible public health hazards. Full article

(This article belongs to the Special Issue Challenges and Strategies for the Antibiotic Resistance Crisis)

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21 pages, 3771 KB

Open AccessArticle

In Silico Identification and Molecular Characterization of Lentilactobacillus hilgardii Antimicrobial Peptides with Activity Against Carbapenem-Resistant Acinetobacter baumannii

by Amanda Appel, Lily Velazco, Adit B. Alreja, Kara LeClair, Aryaan P. Duggal, Isha Vashee, Aji Mary Taal, Norberto Gonzalez-Juarbe and Derrick E. Fouts

Antibiotics 2025, 14(10), 1004; https://doi.org/10.3390/antibiotics14101004 - 10 Oct 2025

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Abstract

Background/Objectives: Biofilm formation by Acinetobacter baumannii contributes to its persistence in clinical settings and resistance to antibiotic treatment. This study aims to identify and characterize antimicrobials from lactic acid bacteria (LAB) using molecular and in silico approaches that can prevent and disrupt A. [...] Read more.

Background/Objectives: Biofilm formation by Acinetobacter baumannii contributes to its persistence in clinical settings and resistance to antibiotic treatment. This study aims to identify and characterize antimicrobials from lactic acid bacteria (LAB) using molecular and in silico approaches that can prevent and disrupt A. baumannii biofilms, assess their antimicrobial host range, and define their synergy with current antibiotics. Methods: Thirteen LAB isolates from the Human Microbiome Project were screened for anti-biofilm activity against A. baumannii. Conditioned media was further tested against six ESKAPE pathogens and three skin commensals. Lentilactobacillus hilgardii was selected for detailed study and antimicrobial peptide (AMP) prediction analysis due to limited toxicity toward commensals. In silico identified peptides were synthesized and tested individually and in combination with sub-MIC doses of an antibiotic. Results: Conditioned media from five LAB species (Lentilactobacillus hilgardii, Lentilactobacillus buchneri, Ligilactobacillus ruminis, Limosilactobacillus fermentum, and Limosilactobacillus antri) significantly inhibited A. baumannii biofilm formation and reduced biomass of mature biofilms. LAB-conditioned media also exhibited broad-spectrum activity against ESKAPE pathogens, though effects on commensals varied. Bioinformatically predicted AMPs from L. hilgardii inhibited planktonic A. baumannii growth but showed no direct biofilm activity even at high doses. However, AMPs were found to synergize with sub-MIC doses of meropenem against mature biofilms leading to decolonization. Conclusions: Our study provides a comprehensive platform for the discovery and characterization of AMPs and supports using commensal bacteria to reduce, prevent, and decolonize biofilms from pathogenic bacteria in community and nosocomial settings. Full article

(This article belongs to the Section Antimicrobial Peptides)

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13 pages, 2544 KB

Open AccessArticle

Bicarinalin Enhances the Antibacterial Activity of Levofloxacin and Clarithromycin Against Helicobacter pylori

by Iman Saleh and Pınar Küce Çevik

Antibiotics 2025, 14(10), 1003; https://doi.org/10.3390/antibiotics14101003 - 10 Oct 2025

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Abstract

Background/Objectives: Helicobacter pylori (H. pylori) is a Gram-negative bacterium that colonizes the human stomach and causes various gastrointestinal diseases. Although antibiotic therapy is the most effective method for its eradication, the increasing prevalence of antibiotic resistance has made treatment increasingly [...] Read more.

Background/Objectives: Helicobacter pylori (H. pylori) is a Gram-negative bacterium that colonizes the human stomach and causes various gastrointestinal diseases. Although antibiotic therapy is the most effective method for its eradication, the increasing prevalence of antibiotic resistance has made treatment increasingly challenging in recent years. In this study, the antimicrobial activity, synergistic effects with antibiotics, and mechanisms of action of Bicarinalin, an antimicrobial peptide (AMP) derived from the venom of Tetramorium bicarinatum, were investigated against H. pylori. Methods: To determine the antibacterial activity of Bicarinalin, a well diffusion assay was performed, yielding an inhibition zone of 18.3 mm at a concentration of 32 µg/mL for ATCC strain. MIC₉₉ values were determined by microdilution tests as 4.8 μg/mL for the reference strain. The enhancement of the antimicrobial potential of levofloxacin and clarithromycin when administered together with Bicarinalin has been demonstrated using the well diffusion method. Results: Inhibition zones increased from 14.2 mm to 20 mm for levofloxacin and from 7.3 mm to 16 mm for clarithromycin. This study is the first to identify DNA and protein leakage caused by Bicarinalin in H. pylori. Intracellular protein and DNA leakage were measured, with protein and DNA levels released into the extracellular environment determined as 33.25% and 55.10%, respectively, following Bicarinalin treatment. Furthermore, to investigate its effect on membrane damage, scanning electron microscopy (SEM) was performed, revealing disrupted cell membrane structures, penetration between cells, and severe deterioration of morphological integrity. Conclusions: This study has demonstrated for the first time that, when administered concomitantly, Bicarinalin enhances the antimicrobial activities of levofloxacin and clarithromycin. This highlights its potential as an adjunctive treatment for H. pylori alongside existing drugs. Full article

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11 pages, 7598 KB

Open AccessArticle

ICECleSHZ29: Novel Integrative and Conjugative Element (ICE)-Carrying Tigecycline Resistance Gene tet(X6) in Chryseobacterium lecithinasegens

by Xi Chen, Yifei Zhang, Chunling Jiang, Yafang Lin, Xiaohui Yao, Wansen Nie, Lin Li, Jianchao Wei, Donghua Shao, Ke Liu, Zongjie Li, Yafeng Qiu, Zhiyong Ma, Beibei Li and Lining Xia

Antibiotics 2025, 14(10), 1002; https://doi.org/10.3390/antibiotics14101002 - 10 Oct 2025

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Abstract

Background/Objectives: The global dissemination of tet(X) variants critically threatens tigecycline efficacy as a last-resort antibiotic. The aim of this study was to characterize a tet(X6)-carrying integrative and conjugative element (ICE) in a multidrug-resistant Chryseobacterium lecithinasegens strain, SHZ29, isolated from Shanghai, China. [...] Read more.

Background/Objectives: The global dissemination of tet(X) variants critically threatens tigecycline efficacy as a last-resort antibiotic. The aim of this study was to characterize a tet(X6)-carrying integrative and conjugative element (ICE) in a multidrug-resistant Chryseobacterium lecithinasegens strain, SHZ29, isolated from Shanghai, China. Methods: Minimum inhibitory concentrations (MICs) were determined by broth microdilution for SHZ29. Whole genomic sequencing and bioinformatic analysis were performed to depict the structure of the novel tet(X6)-carrying ICE. Inverse PCR and conjugation experiments were conducted to investigate the transfer ability of the ICE. Results: We depicted a novel tet(X6)-carrying ICE, named ICECleSHZ29, which is 74,906 bp in size and inserted into the 3′ end of tRNA-Met-CAT gene of the C. lecithinasegens strain SHZ29, with 17 bp direct repeats (5′-tcccgtcttcgctacaa-3′). This ICE possesses a 38 kb conserved backbone and four variable regions (VR1-4), with VR3 aggregating multiple resistance genes, including tet(X6), tet(X2), erm(F), ere(D), floR, catB, sul2, ant(6)-I and bla_OXA-1327. NCBI database searching identified 13 additional ICEs sharing a similar backbone to ICECleSHZ29. These ICECleSHZ29-like ICEs could be classified into two types based on their distinct insertion sites: Type I, inserted at the tRNA-Met-CAT gene; and Type II, inserted at the tRNA-Glu-TTC gene. Phylogenetic analysis indicated that differences in integrases may result in differences in the insertion site among these ICEs. A circular intermediate form of ICECleSHZ29 was detected by inverse PCR. However, the conjugation experiments using Escherichia coli EC600 as recipients failed. Conclusions: To our knowledge, this study provides the first report of tet(X6) in C. lecithinasegens and characterizes its carrier, a novel ICE: ICECleSHZ29. Full article

(This article belongs to the Special Issue Antibiotic Resistance in Agricultural Environments: Emergence, Drivers and Mitigation)

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12 pages, 1253 KB

Open AccessArticle

Rapid Nanopore Sequencing of Positive Blood Cultures Using Automated Benzyl-Alcohol Extraction Improves Time-Critical Sepsis Management

by Chi-Sheng Tai, Hsing-Yi Chung, Tai-Han Lin, Chih-Kai Chang, Cherng-Lih Perng, Po-Shiuan Hsieh, Hung-Sheng Shang and Ming-Jr Jian

Antibiotics 2025, 14(10), 1001; https://doi.org/10.3390/antibiotics14101001 - 9 Oct 2025

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Abstract

Background/Objective: Timely identification of bloodstream pathogens is critical for sepsis management; however, PCR inhibitors such as sodium polyanetholesulfonate (SPS) in blood culture broth compromise nucleic acid recovery and long read sequencing. We assessed whether coupling a benzyl alcohol SPS-removal step to the [...] Read more.

Background/Objective: Timely identification of bloodstream pathogens is critical for sepsis management; however, PCR inhibitors such as sodium polyanetholesulfonate (SPS) in blood culture broth compromise nucleic acid recovery and long read sequencing. We assessed whether coupling a benzyl alcohol SPS-removal step to the fully automated LabTurbo AIO extractor improves Oxford Nanopore-based pathogen detection. Methods: Thirteen positive blood culture broths were pre-treated with benzyl alcohol and divided: half volumes were purified on the LabTurbo AIO; paired aliquots underwent manual QIAamp extraction. DNA purity was evaluated by NanoDrop and Qubit. Barcoded libraries were sequenced on MinION R9.4.1 flow cells for 6 h. Results: Automated eluates showed a median A₂₆₀/A₂₈₀ of 1.92 and A₂₆₀/A₂₃₀ of 1.96, versus 1.80 and 1.48 for manual extracts. The automated workflow generated 1.69 × 10⁶ total reads compared with 3.9 × 10⁵ reads for manual extraction. The median N50 read length increased from 5.9 kb to 8.7 kb, and the median proportion of reads classified to species increased from 62% to 84%. The hands-on time was <5 min and the sample-to-answer turnaround was <8 h, compared with >9 h and 90 min for the manual protocol, respectively. Conclusions: Benzyl alcohol SPS removal integrated into the LabTurbo AIO extractor yielded purer, longer, and higher read counts, enhancing nanopore sequencing depth and accuracy while compressing diagnostic turnaround to a single working day. This represents a practical advance for rapid blood culture pathogen identification in critical care settings. Full article

(This article belongs to the Special Issue Surveillance and Detection of Antimicrobial Resistance: Tools and Trends)

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19 pages, 874 KB

Open AccessReview

Decoding Mastitis in Small Rodent Pets: Pathophysiology, Antimicrobial Resistance Profiles, and Future Directions in Treatment Strategies

by Raul Alexandru Pop, Iosif Vasiu, Cosmina-Andreea Dejescu, Piera Anna Martino, Marco Wochnik and Roman Dąbrowski

Antibiotics 2025, 14(10), 1000; https://doi.org/10.3390/antibiotics14101000 - 9 Oct 2025

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Abstract

Background: Mastitis is a condition affecting various animals, including hamsters, gerbils, mice, and rats. While these species are frequently used as models for studying mammary gland infections in biomedical research, there is limited understanding of their natural occurrence, epidemiology, and management. This review [...] Read more.

Background: Mastitis is a condition affecting various animals, including hamsters, gerbils, mice, and rats. While these species are frequently used as models for studying mammary gland infections in biomedical research, there is limited understanding of their natural occurrence, epidemiology, and management. This review examines the anatomy, causes, clinical signs, pathology, and treatment of mastitis in small pet rodents, highlighting existing knowledge gaps and emphasizing the need for further research. To the best of the author’s knowledge, this is the first review focusing on mastitis in small pet rodents, underlining the importance of maintaining mammary gland health in these pets. Full article

(This article belongs to the Special Issue Gram-Negative Infections in Humans and Companion Animals: A Global Threat)

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13 pages, 2060 KB

Open AccessArticle

Effect of Meropenem, Sulbactam, and Colistin Combinations on Resistance Gene Expression in Multidrug-Resistant A. baumannii Clinical Isolates from Panama

by José Emigdio Moreno, Jordi Querol-Audi, Ariel Magallón Tejada, Juan R. Medina-Sánchez and Armando Durant Archibold

Antibiotics 2025, 14(10), 999; https://doi.org/10.3390/antibiotics14100999 - 7 Oct 2025

Viewed by 349

Abstract

Background: Given the increasing problem of antibiotic resistance in A. baumannii, this study examines in vitro how combinations of colistin, meropenem, and sulbactam influence the expression of genes associated with multiresistance in this pathogen. Methods: Three multidrug-resistant strains, isolated from clinical infections [...] Read more.

Background: Given the increasing problem of antibiotic resistance in A. baumannii, this study examines in vitro how combinations of colistin, meropenem, and sulbactam influence the expression of genes associated with multiresistance in this pathogen. Methods: Three multidrug-resistant strains, isolated from clinical infections in Panama (2022–2023), were identified using Vitek 2 compact. Susceptibility by broth microdilution, qualitative synergy, time-kill curves, and gene expression analysis by quantitative PCR were performed. Results: Synergistic effects were observed for the colistin–meropenem combination in all three strains, while the sulbactam–colistin combination exhibit synergy only in one of the A. baumannii isolates. Time-kill assays revealed bactericidal effects for the colistin–meropenem and sulbactam–colistin combinations. qPCR analyses indicated that colistin, meropenem, and sulbactam modified the expression of the genes under study. Colistin–meropenem and meropenem–sulbactam combinations decreased the expression of blaADC and blaOXA-51, while sulbactam–colistin did not have a significant effect. carO expression levels were not reduced with any antibiotic combination, while adeB expression was reduced with all the combinations tested. omp33–36 expression varied depending on the antibiotic and strain. Conclusions: Therefore, this study offers a new perspective on how rational combinations of clinically used antibiotics have the potential to modulate gene expression and contribute to the control of MDR strains, indicating that high-dose combination therapy with sulbactam and colistin could offer improved efficacy in treating multidrug resistant Acinetobacter baumannii infections. Full article

(This article belongs to the Special Issue Genetics and Antimicrobial Resistance in Pathogens of Hospital Importance)

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21 pages, 785 KB

Open AccessArticle

Antimicrobial Prophylaxis for Recurrent Urinary Tract Infections in Premenopausal and Postmenopausal Women: A Retrospective Observational Study from an Outpatient Clinic in a Tertiary University Hospital

by Tomislava Skuhala, Marin Rimac, Vladimir Trkulja and Snjezana Zidovec-Lepej

Antibiotics 2025, 14(10), 998; https://doi.org/10.3390/antibiotics14100998 - 5 Oct 2025

Viewed by 505

Abstract

Background: Recurrent urinary tract infections (rUTIs) significantly impair women’s quality of life, making antimicrobial prophylaxis a critical preventative strategy. This retrospective observational study aimed to characterize antibiotic prophylaxis patterns, relapse rates, comparative efficacy of different agents, and tolerability in 908 women (663 postmenopausal, [...] Read more.

Background: Recurrent urinary tract infections (rUTIs) significantly impair women’s quality of life, making antimicrobial prophylaxis a critical preventative strategy. This retrospective observational study aimed to characterize antibiotic prophylaxis patterns, relapse rates, comparative efficacy of different agents, and tolerability in 908 women (663 postmenopausal, 245 premenopausal) with rUTIs managed at a tertiary university hospital. Methods: Data from medical records (January 2022–December 2024) were analyzed. Patients were stratified by menopausal status. We assessed antibiotic usage, relapse rates (per 100 patient-months), and adverse events. Comparative efficacy of nitrofurantoin-based versus fosfomycin/other prophylaxis was evaluated for rUTIs caused by E. coli, E. faecalis, or E. coli ESBL using weighted and matched analyses to control for covariates. Results: Continuous antimicrobial prophylaxis was the primary strategy, with nitrofurantoin being most frequently used. Premenopausal women showed a greater tendency for intermittent or combined prophylactic approaches. Postmenopausal women exhibited a higher overall crude relapse rate (5.54/100 p-m) compared to premenopausal women (3.14/100 p-m), with E. coli being the most common causative agent in relapses. For rUTIs caused by E. coli, E. faecalis, or E. coli ESBL, nitrofurantoin-based prophylaxis demonstrated significantly lower adjusted relapse rates than fosfomycin/other regimens (rate ratio: 0.47 for postmenopausal, 0.35 for premenopausal women). This observed efficacy for nitrofurantoin was robust against potential unmeasured confounding. Prophylaxis was generally well-tolerated (3.0% gastrointestinal adverse events overall); however, premenopausal women reported a higher adverse event incidence. Conclusions: Our findings strongly suggest that nitrofurantoin is an effective prophylactic choice for rUTIs caused by common uropathogens (E. coli, E. faecalis, E. coli ESBL), particularly in postmenopausal women. The diverse prophylactic strategies highlight the need for individualized care. While generally well-tolerated, adverse event profiles vary between menopausal groups, necessitating careful monitoring. Full article

(This article belongs to the Section Antibiotic Therapy in Infectious Diseases)

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14 pages, 1846 KB

Open AccessReview

New Antibiotics for Treating Infections Caused by Multidrug-Resistant Bacteria

by Elisabete Machado and João Carlos Sousa

Antibiotics 2025, 14(10), 997; https://doi.org/10.3390/antibiotics14100997 - 5 Oct 2025

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Abstract

Infections caused by antibiotic resistant bacteria pose a serious threat to global health, leading to higher medical costs, longer hospital stays, and increased morbidity and mortality. An increasing number of bacteria have been implicated in untreatable infections due to multiple resistance mechanisms. In [...] Read more.

Infections caused by antibiotic resistant bacteria pose a serious threat to global health, leading to higher medical costs, longer hospital stays, and increased morbidity and mortality. An increasing number of bacteria have been implicated in untreatable infections due to multiple resistance mechanisms. In 2017, the World Health Organization published a list of the most important antibiotic resistant bacteria worldwide, for which there is an urgent need to develop new therapeutic options. In recent years, fortunately, new antibiotics have been approved for the treatment of infections caused by multidrug-resistant bacteria. The purpose of this review is to present the most impactful new antibiotics that are currently available for the treatment of these infections. The discovery of new therapeutic strategies will help to limit the spread of multidrug-resistant bacteria, but careful prescribing, appropriate use and monitoring of resistant strains will be crucial to ensure that they remain effective in the future. Full article

(This article belongs to the Special Issue Hospital-Associated Infectious Diseases and Antibiotic Therapy)

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13 pages, 388 KB

Open AccessReview

Does Vancomycin as the First-Choice Therapy for Antibiotic Prophylaxis Increase the Risk of Surgical Site Infections Following Spine Surgery?

by Vojislav Bogosavljevic, Dusan Spasic, Lidija Stanic, Marija Kukuric and Milica Bajcetic

Antibiotics 2025, 14(10), 996; https://doi.org/10.3390/antibiotics14100996 - 5 Oct 2025

Viewed by 430

Abstract

Surgical site infections (SSIs) remain a significant complication in spine surgery, especially in instrumented procedures with long operative times. Although guidelines recommend cefazolin as the first-line agent due to its efficacy against Staphylococcus aureus, predictable pharmacokinetics, and safety, its real-world practice is highly [...] Read more.

Surgical site infections (SSIs) remain a significant complication in spine surgery, especially in instrumented procedures with long operative times. Although guidelines recommend cefazolin as the first-line agent due to its efficacy against Staphylococcus aureus, predictable pharmacokinetics, and safety, its real-world practice is highly variable, with inappropriate and prolonged regimens reported across Europe. Vancomycin is often used as the first choice of therapy empirically and without screening, exposing patients to risks such as delayed infusion, nephrotoxicity, and the emergence of vancomycin-resistant enterococci (VRE).This review assesses the present function of vancomycin in relation to cefazolin for spinal prophylaxis and examines wider trends in the misuse of surgical antibiotic prophylaxis, which were identified through PubMed and Scopus searches. Evidence from randomized and prospective studies consistently supports cefazolin as the preferred prophylactic agent in clean spinal surgery. Observational data suggest that adjunctive or topical vancomycin may reduce infection rates in selected high-risk or revision cases, though the results are inconsistent and frequently limited by retrospective designs and heterogeneous outcome reporting. Importantly, the most rigorous randomized controlled trial found no benefit of intrawound vancomycin over the placebo. A small number of available investigations in vancomycin use with major design limitations have resulted in no significant VRE emergency. Unexpectedly, widespread use of vancomycin was followed by a notable transition toward Gram-negative and opportunistic organisms. In summary, vancomycin may only be considered in patients with documented MRSA colonization, β-lactam allergy, or selected revision procedures, but its widespread empirical use as a first-choice therapy is not supported. Full article

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24 pages, 1623 KB

Open AccessReview

Beyond the Resistome: Molecular Insights, Emerging Therapies, and Environmental Drivers of Antibiotic Resistance

by Nada M. Nass and Kawther A. Zaher

Antibiotics 2025, 14(10), 995; https://doi.org/10.3390/antibiotics14100995 - 4 Oct 2025

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Abstract

Antibiotic resistance remains one of the most formidable challenges to modern medicine, threatening to outpace therapeutic innovation and undermine decades of clinical progress. While resistance was once viewed narrowly as a clinical phenomenon, it is now understood as the outcome of complex ecological [...] Read more.

Antibiotic resistance remains one of the most formidable challenges to modern medicine, threatening to outpace therapeutic innovation and undermine decades of clinical progress. While resistance was once viewed narrowly as a clinical phenomenon, it is now understood as the outcome of complex ecological and molecular interactions that span soil, water, agriculture, animals, and humans. Environmental reservoirs act as silent incubators of resistance genes, with horizontal gene transfer and stress-induced mutagenesis fueling their evolution and dissemination. At the molecular level, advances in genomics, structural biology, and systems microbiology have revealed intricate networks involving plasmid-mediated resistance, efflux pump regulation, integron dynamics, and CRISPR-Cas interactions, providing new insights into the adaptability of pathogens. Simultaneously, the environmental dimensions of resistance, from wastewater treatment plants and aquaculture to airborne dissemination, highlight the urgency of adopting a One Health framework. Yet, alongside this growing threat, novel therapeutic avenues are emerging. Innovative β-lactamase inhibitors, bacteriophage-based therapies, engineered lysins, antimicrobial peptides, and CRISPR-driven antimicrobials are redefining what constitutes an “antibiotic” in the twenty-first century. Furthermore, artificial intelligence and machine learning now accelerate drug discovery and resistance prediction, raising the possibility of precision-guided antimicrobial stewardship. This review synthesizes molecular insights, environmental drivers, and therapeutic innovations to present a comprehensive landscape of antibiotic resistance. By bridging ecological microbiology, molecular biology, and translational medicine, it outlines a roadmap for surveillance, prevention, and drug development while emphasizing the need for integrative policies to safeguard global health. Full article

(This article belongs to the Special Issue Antimicrobial Resistance and Environmental Health, 2nd Edition)

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14 pages, 279 KB

Open AccessArticle

Significant Prevalence of Dual KPC/NDM Carbapenemase-Producing Klebsiella pneumoniae in an ICU Cohort in Thessaloniki (2023), Including an ST512 Isolate Co-Harboring bla_NDM-1 and bla_KPC-3

by Maria Chatzidimitriou, Apostolos Voulgaridis, Pandora Tsolakidou, Fani Chatzopoulou, Ioannis Chonianakis, Eleni Vagdatli, Melania Kachrimanidou and Timoleon-Achilleas Vyzantiadis

Antibiotics 2025, 14(10), 994; https://doi.org/10.3390/antibiotics14100994 - 4 Oct 2025

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Abstract

Background/Objectives: Carbapenem-resistant Klebsiella pneumoniae (CRKP) threatens Intensive Care Units (ICU), particularly in settings where serine (KPC) and metallo-β-lactamases (NDM) co-circulate. The aim of this study was to assess CRKP susceptibility especially to novel β-lactam/β-lactamase inhibitor combinations, characterize the genetic determinants of resistance, [...] Read more.

Background/Objectives: Carbapenem-resistant Klebsiella pneumoniae (CRKP) threatens Intensive Care Units (ICU), particularly in settings where serine (KPC) and metallo-β-lactamases (NDM) co-circulate. The aim of this study was to assess CRKP susceptibility especially to novel β-lactam/β-lactamase inhibitor combinations, characterize the genetic determinants of resistance, and contribute to the understanding of local epidemiology in the ICU of our hospital. Methods: We studied 32 non-duplicate CRKP isolates (30 ICU, 2 wards) collected at Hippokration General Hospital, Thessaloniki (May–Oct 2023). Bacterial identification and Antimicrobial susceptibility testing (AST) were performed by VITEK-2; Minimum inhibitory concentrations (MICs) for ceftazidime/avibactam (CAZ/AVI), meropenem/vaborbactam (MER/VAB), and imipenem/relebactam (IMI/REL) were determined by E-tests. Colistin MICs were performed by broth microdilution. Carbapenemases were screened phenotypically and by immunochromatography and confirmed by multiplex PCR. One bronchial isolate co-harboring bla_NDM and bla_KPC genes underwent WGS. Results: All isolates were carbapenem-resistant and showed extensive resistance to β-lactams and fluoroquinolones. By PCR, 8/32 (25%) carried bla_KPC alone, 8/32 (25.0%) bla_NDM alone, and 16/32 (50%) co-harbored bla_KPC and bla_NDM. KPC-only isolates were generally susceptible in vitro to CAZ/AVI, MER/VAB, and IMI/REL, whereas dual KPC-NDM producers were resistant to all three combinations. Tigecycline showed the highest retained activity; colistin remained active in a minority. WGS of one ST512 (CG258) isolate revealed co-harboring bla_NDM-1 and bla_KPC-3 with additional resistance determinants and plasmid replicons, consistent with high-risk spread. Conclusions: Half of CRKP isolates in this ICU-predominant series co-produced KPC and NDM, severely limiting β-lactam/β-lactamase inhibitor options. These data support routine screening for carbapenemases, strict infection prevention, antimicrobial stewardship, and access to agents active against MBLs. Full article

(This article belongs to the Special Issue Epidemiology and Genomics of Antimicrobial Resistance of Difficult-to-Treat Pathogens)

12 pages, 623 KB

Open AccessArticle

Isavuconazole-Amphotericin B and Isavuconazole-Caspofungin In Vitro Synergic Activity Against Invasive Pulmonary Aspergillosis Molds Isolates

by Maddalena Calvo, Michelangelo Caruso, Adriana Antonina Tempesta and Laura Trovato

Antibiotics 2025, 14(10), 993; https://doi.org/10.3390/antibiotics14100993 - 4 Oct 2025

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Abstract

Background/Objectives: Invasive pulmonary aspergillosis (IPA) represents a critical respiratory condition mainly caused by Aspergillus fumigatus and other ubiquitous species such as Aspergillus flavus, Aspergillus niger, and Aspergillus terreus. IPA clinical management has been complicated by diagnostic challenges and therapeutic [...] Read more.

Background/Objectives: Invasive pulmonary aspergillosis (IPA) represents a critical respiratory condition mainly caused by Aspergillus fumigatus and other ubiquitous species such as Aspergillus flavus, Aspergillus niger, and Aspergillus terreus. IPA clinical management has been complicated by diagnostic challenges and therapeutic difficulties due to antifungal intrinsic or secondary resistance episodes. Despite this assumption, few scientific data have been reported about possible antifungal drug combinations. Herein, we propose an experimental evaluation using isavuconazole/amphotericin B and isavuconazole/caspofungin in vitro synergy assays to investigate their combined activity on Aspergillus spp. IPA clinical isolates. Methods: We globally analyzed 55 Aspergillus spp. isolates, practicing the gradient test methods with single and combined antifungal drugs through the MIC Strip test (Liofilchem, Roseto degli Abruzzi, Italy). The collected MIC values were interpreted according to the EUCAST guidelines and classified as synergy, additivity, indifference, and antagonism cases through a FIC index calculation. A statistical analysis on species’ correlation with particular synergy testing results was finally provided. Results: Despite an interesting activity against A. fumigatus, isavuconazole/amphotericin B did not report statistical significance, obtaining a consistent antagonism percentage (43.6%). On the other hand, isavuconazole/caspofungin showed a promising in vitro synergic activity, except for A. flavus isolates. Conclusions: Synergy testing demonstrated a significant species-specific trend. Future studies should be focused on Aspergillus spp. isolates and antifungal in vitro synergy testing, aiming to discourage or recommend any specific antifungal combinations, depending on the isolated species. Full article

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15 pages, 1075 KB

Open AccessArticle

Synergistic Antibacterial Activity of Azithromycin-Loaded Chitosan Nanoparticles Alone and in Combination with Cetirizine Dihydrochloride Against Resistant Isolates of Respiratory Tract Infections

by Umbreen Anwar, Adeel Sattar, Muhammad Adil Rasheed, Muhammad Abu Bakr Shabbir and Mateen Abbas

Antibiotics 2025, 14(10), 992; https://doi.org/10.3390/antibiotics14100992 - 3 Oct 2025

Viewed by 430

Abstract

Background/Objectives: Antibiotic resistance is a major public health concern, with considerable socio-economic consequences. Researchers are exploring alternative strategies, including nanotechnology, which has shown significance in targeted drug delivery. This study evaluates the synergistic antibacterial activity of azithromycin-loaded chitosan nanoparticles (AZM-CSNPs) against azithromycin-resistant clinical [...] Read more.

Background/Objectives: Antibiotic resistance is a major public health concern, with considerable socio-economic consequences. Researchers are exploring alternative strategies, including nanotechnology, which has shown significance in targeted drug delivery. This study evaluates the synergistic antibacterial activity of azithromycin-loaded chitosan nanoparticles (AZM-CSNPs) against azithromycin-resistant clinical respiratory isolates of methicillin-resistant Staphylococcus aureus (MRSA) and Klebsiella pneumoniae (K. pneumoniae). Methods: A total of 87 sputum samples (n = 87) were collected and analyzed. The ermB gene for K. pneumoniae and the ermA gene for MRSA were used to confirm resistant isolates. Among 87 samples, 29 manifested K. pneumoniae, and 32 exhibited MRSA-positive cultures, confirmed through phenotypic and genotypic methods. The RT-PCR is performed by using a cDNA Kit to determine the gene expression. Results: The results elucidate resistance of K. pneumoniae against several antibiotics, including azithromycin (15 µg), chloramphenicol (30 µg), and amoxicillin (30 µg), while MRSA also showed resistance to cefoxitin (30 µg), azithromycin (15 µg), and gentamycin (10 µg). Reduction in the MIC value of the nanoparticle formulation showed their effectiveness. The AZM-CSNPs combined with cetirizine dihydrochloride helped to down-regulate the resistant genes. Conclusions: Notably, a strong synergistic effect was observed with AZM-CSNPs in combination with cetirizine, significantly enhancing antibacterial efficacy against resistant isolates. Full article

(This article belongs to the Special Issue New Insights Toward the Development of Novel Inhibitors of S. aureus and P. aeruginosa Factors)

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25 pages, 1464 KB

Open AccessArticle

STOP Strategy to Inhibit P. falciparum and S. aureus Growth: Molecular Mechanism Studies on Purposely Designed Hybrids

by Beatrice Gianibbi, Riccardo Corina, Nicoletta Basilico, Ottavia Spiga, Silvia Gobbi, Federica Belluti, Giovanna Angela Gentilomi, Silvia Parapini, Francesca Bonvicini and Alessandra Bisi

Antibiotics 2025, 14(10), 991; https://doi.org/10.3390/antibiotics14100991 - 3 Oct 2025

Viewed by 415

Abstract

Background/Objectives: Malaria remains the most critical parasitic disease globally, responsible for over 600.000 deaths annually. In sub-Saharan Africa, co-infections of Plasmodium falciparum with other pathogens, particularly Staphylococcus aureus, are common in children with severe malaria. Therefore, the design of new compounds [...] Read more.

Background/Objectives: Malaria remains the most critical parasitic disease globally, responsible for over 600.000 deaths annually. In sub-Saharan Africa, co-infections of Plasmodium falciparum with other pathogens, particularly Staphylococcus aureus, are common in children with severe malaria. Therefore, the design of new compounds targeting both pathogens appears to be an urgent priority. Methods: A small series of hybrid compounds was designed and synthesized by linking the pharmacophore of the antimalarial drug chloroquine with the phenothiazine core. These compounds were tested in vitro against a panel of microbial strains and further analyzed through in silico simulations to predict their physical-chemical properties. Results: Compounds 4b and 5b emerged the most potent candidates of the series, showing a sub-micromolar inhibitory activity on P. falciparum, and a promising micromolar potency on S. aureus alongside with a low toxicity on mammalian cells. Molecular docking followed by molecular dynamics (MD) simulations identified the respiratory membrane NDH-2 enzyme as common target in both pathogens. Conclusions: Both experimental and computational findings provide compelling evidence for the use of the designed compounds in a STOP strategy, i.e., Same-Target-Other-Pathogen, to treat malaria and bacterial infections concurrently. Full article

(This article belongs to the Special Issue Discovery and Design of New Antimicrobial Agents)

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13 pages, 473 KB

Open AccessArticle

Comparison of Vonoprazan and Low-Dose Amoxicillin Dual Therapy with Bismuth-Containing Quadruple Therapy for Naïve Helicobacter pylori Eradication: A Single-Center, Open-Label, Randomized Control Trial

by Xue Fan, Yanyan Shi, Yuan Li and Xiangchun Lin

Antibiotics 2025, 14(10), 990; https://doi.org/10.3390/antibiotics14100990 - 3 Oct 2025

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Abstract

Objective: This study aimed to compare the effectiveness and safety of vonoprazan–amoxicillin (VA) dual therapy with modified bismuth-containing quadruple therapy (esomeprazole, bismuth, amoxicillin, and clarithromycin; EBAC) in treatment-naïve patients infected with Helicobacter pylori (H. pylori). Methods: In this single-center, open-label, randomized [...] Read more.

Objective: This study aimed to compare the effectiveness and safety of vonoprazan–amoxicillin (VA) dual therapy with modified bismuth-containing quadruple therapy (esomeprazole, bismuth, amoxicillin, and clarithromycin; EBAC) in treatment-naïve patients infected with Helicobacter pylori (H. pylori). Methods: In this single-center, open-label, randomized controlled trial conducted from July to December 2024, a total of 504 H. pylori-positive patients were randomly allocated to receive either VA (vonoprazan 20 mg and amoxicillin 1000 mg, twice daily for 14 days) or EBAC (esomeprazole 20 mg bid, bismuth potassium citrate 220 mg bid, amoxicillin 1000 mg bid, clarithromycin 500 mg bid, twice daily for 14 days). The primary endpoint was the H. pylori eradication rate, and the secondary endpoint was safety. Results: In the intention-to-treat (ITT) analysis, the eradication rates were 79.4% (200/252) in the VA group and 85.7% (216/252) in the EBAC group (p = 0.060). Per-protocol (PP) analysis showed comparable eradication rates between the two groups (92.1% [197/214] vs. 93.0% [213/229], p = 0.712), confirming the non-inferiority of VA compared to EBAC. The incidence of adverse events was significantly fewer in the VA group (27.2% vs. 42.7%, p < 0.001). Logistic regression identified medication adherence (≥80%) as the only independent predictor of successful eradication (OR 17.557, p < 0.001). Conclusions: VA dual therapy achieved comparable H. pylori eradication rates to EBAC, while offering better safety and a more convenient regimen, supporting it as a preferred first-line treatment for H. pylori infection. Full article

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11 pages, 260 KB

Open AccessArticle

Evaluation of the NG-Test CARBA 5 for Rapid Detection of Carbapenemases in Clinical Isolates of Klebsiella pneumoniae

by Bojan Rakonjac, Momčilo Djurić, Danijela Djurić-Petković, Jelena Dabić, Marko Simonović, Marija Milić and Aleksandra Arsović

Antibiotics 2025, 14(10), 989; https://doi.org/10.3390/antibiotics14100989 - 2 Oct 2025

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Abstract

Background: Carbapenem-resistant Klebsiella pneumoniae (CRKp) is a critical global health threat due to its multidrug resistance, primarily driven by carbapenemase production. Rapid and accurate detection of carbapenemases is essential for effective treatment and infection control. This study evaluates the validity of the NG-Test [...] Read more.

Background: Carbapenem-resistant Klebsiella pneumoniae (CRKp) is a critical global health threat due to its multidrug resistance, primarily driven by carbapenemase production. Rapid and accurate detection of carbapenemases is essential for effective treatment and infection control. This study evaluates the validity of the NG-Test CARBA 5, a rapid immunochromatographic assay, for detecting five major carbapenemases (KPC, NDM, VIM, IMP, OXA-48-like) in clinical CRKp isolates. Methods: Clinical isolates of CRKp were collected from various clinical specimens at the Military Medical Academy in Belgrade, Serbia, between January 2023 and October 2024. Detection of carbapenemases was performed using NG-Test CARBA 5, while PCR served as the reference method. Diagnostic performance was assessed by calculating sensitivity, specificity, and Cohen’s kappa coefficient. Results: Among 312 isolates, OXA-48-like was the most prevalent carbapenemase. NG-Test CARBA 5 showed high sensitivity (98.7%) and specificity (100%) overall, with excellent agreement for NDM (κ = 0.947), OXA-48-like (κ = 0.957), and KPC (κ = 0.978). However, it failed to detect VIM in five PCR-positive isolates, suggesting potential limitations. Conclusions: NG-Test CARBA 5 is a rapid and reliable tool for detecting major carbapenemases in CRKp, though its performance for VIM detection requires further investigation. This assay has the potential to improve clinical diagnostics and strengthen infection control in settings with high antimicrobial resistance. Full article

(This article belongs to the Special Issue Advancing and Standardising Antimicrobial Susceptibility and Resistance Detection Methodology)

14 pages, 1339 KB

Open AccessArticle

Repurposed Drugs and Efflux Pump Inhibitors Against Gram-Negative Urinary Tract Pathogenic Bacteria

by Annamária Kincses, Márta Nové, Jina Asefi and Gabriella Spengler

Antibiotics 2025, 14(10), 988; https://doi.org/10.3390/antibiotics14100988 - 2 Oct 2025

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Abstract

Background/Objectives: Urinary tract infections (UTIs) represent a major healthcare challenge due to antimicrobial resistance and biofilm formation. Our aim was to evaluate whether repurposed drugs and efflux pump inhibitors (EPIs) could provide alternative strategies by investigating their antibacterial, anti-biofilm, and resistance-modifying properties [...] Read more.

Background/Objectives: Urinary tract infections (UTIs) represent a major healthcare challenge due to antimicrobial resistance and biofilm formation. Our aim was to evaluate whether repurposed drugs and efflux pump inhibitors (EPIs) could provide alternative strategies by investigating their antibacterial, anti-biofilm, and resistance-modifying properties against Gram-negative uropathogens under varying pH conditions. Methods: Clinical isolates of Escherichia coli, Klebsiella pneumoniae, and Proteus mirabilis were tested. Minimum inhibitory concentrations (MICs) of thioridazine (TZ), promethazine (PMZ), fluoxetine (Fx), sertraline (Sr), phenylalanine arginine β-naphthylamide (PAβN), carbonyl cyanide m-chlorophenyl hydrazone (CCCP), and the glutamine uptake inhibitor V9302 were determined at pH 5–8. Biofilm inhibition was assessed by crystal violet staining, while MIC reduction assays tested antibiotic combinations. Efflux pump inhibition was examined using an ethidium bromide accumulation assay. Results: TZ reduced biofilm formation in sensitive K. pneumoniae at all pH levels and enhanced ciprofloxacin (CIP) activity, whereas PMZ showed a weaker effect, limited mainly to neutral pH. Fx and Sr exhibited pH-dependent anti-biofilm activity, with Fx particularly effective against P. mirabilis at alkaline pH. PAβN consistently decreased biofilm biomass in both sensitive and resistant K. pneumoniae and, at pH 7–8, potentiated CIP activity with a 16-fold MIC reduction in the sensitive strain. CCCP showed pH-dependent activity, with stronger effects under acidic conditions, notably in E. coli and P. mirabilis. V9302 was a potent biofilm inhibitor in K. pneumoniae and resistant E. coli and interfered with efflux activity, showing strong effects in acidic environments. Conclusions: Repurposed drugs and EPIs may be useful as antibiotic adjuvants or biofilm inhibitors in treating resistant UTIs. Full article

(This article belongs to the Special Issue New Inhibitors for Overcoming Antimicrobial Resistance)

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Antibiotics, Volume 14, Issue 10 (October 2025) – 60 articles

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