Antibiotics

33 pages, 3365 KiB

Open AccessReview

Colourful Protection: Challenges and Perspectives of Antibacterial Pigments Extracted from Bacteria for Textile Applications

by Micaela Gomes, Helena P. Felgueiras, Barbara R. Leite and Graça M. B. Soares

Antibiotics 2025, 14(5), 520; https://doi.org/10.3390/antibiotics14050520 (registering DOI) - 17 May 2025

Abstract

Bacterial pigments have gained significant attention across multiple industries due to their natural hues and unique functional properties. Beyond coloration, some of these pigments exhibit antibacterial activity, making them particularly valuable in the textile industry as sustainable alternatives to synthetic antimicrobial treatments. Bacteria [...] Read more.

Bacterial pigments have gained significant attention across multiple industries due to their natural hues and unique functional properties. Beyond coloration, some of these pigments exhibit antibacterial activity, making them particularly valuable in the textile industry as sustainable alternatives to synthetic antimicrobial treatments. Bacteria produce a vast array of pigments through diverse biosynthetic pathways, which reflect their metabolic adaptability and ecological roles. These pathways are influenced by environmental factors such as pH, temperature, and nutrient availability. Key pigments, including carotenoids, melanin, violacein, and prodigiosin, are synthesised through distinct mechanisms, often involving tightly regulated enzymatic reactions. For example, carotenoid biosynthesis relies on isoprenoid precursors, while melanin formation involves the oxidation of aromatic amino acids. Understanding these pathways provides insights into bacterial survival strategies, stress responses, and interactions with their environment. This review examines the dyeing potential of bacterial pigments on natural and synthetic fabrics, highlighting advancements in environmentally friendly extraction methods to minimise the ecological impact. Additionally, it explores safety, biocompatibility, and industrial challenges associated with bacterial pigment applications. Finally, future perspectives on integrating these pigments into various industries are discussed, emphasising their potential as bio-based solutions for sustainable and functional materials. Full article

(This article belongs to the Special Issue Microbial Natural Products as a Source of Novel Antimicrobials, 2nd Edition)

► Show Figures

Graphical abstract

12 pages, 226 KiB

Open AccessArticle

Non-Susceptibility of Early-Onset Sepsis Pathogens to the Combination of Ampicillin and Gentamicin Among Neonates in Thailand

by Anucha Thatrimontrichai, Pattima Pakhathirathien, Manapat Praditaukrit, Gunlawadee Maneenil and Supaporn Dissaneevate

Antibiotics 2025, 14(5), 519; https://doi.org/10.3390/antibiotics14050519 (registering DOI) - 17 May 2025

Abstract

Background/Objectives: Empirical antimicrobial therapy for neonatal early-onset sepsis (EOS) comprises ampicillin and gentamicin. However, multidrug-resistant organisms are increasing worldwide, thus inflicting a global burden. We identified the incidence and risk factors of neonates with pathogenic isolates that were not susceptible to treatment [...] Read more.

Background/Objectives: Empirical antimicrobial therapy for neonatal early-onset sepsis (EOS) comprises ampicillin and gentamicin. However, multidrug-resistant organisms are increasing worldwide, thus inflicting a global burden. We identified the incidence and risk factors of neonates with pathogenic isolates that were not susceptible to treatment comprising a combination of ampicillin and gentamicin (non-susceptible group). Methods: This retrospective study included neonates diagnosed with EOS between 2004 and 2023. All patients with EOS and positive culture results within 72 h of birth were reviewed. Patients in the non-susceptible and susceptible groups were analyzed using a multivariable logistic regression model. Results: Sixty pathogenic isolates and 55 neonates with EOS were observed over the course of 20 years. The incidence and case fatality rates of EOS were 0.88 per 1000 live births and 41.8%, respectively. Acinetobacter baumannii was the most common EOS pathogenic isolate (19/60 pathogenic isolates; 12/19 resistant to carbapenems). Pathogenic isolates were susceptible to ampicillin or gentamicin (59%), ampicillin or cefotaxime (42%), and ampicillin or amikacin (72%). Data regarding susceptibility to ampicillin and gentamicin of 49 neonates were available. A multivariable analysis revealed that patients in the non-susceptible group (n = 18) were more likely to experience late-onset EOS (48–72 h; p = 0.01) and require endotracheal intubation on day 1 (p = 0.04) compared to patients in the susceptible group (n = 31). Conclusions: In areas with high multidrug resistance, broader-spectrum antibiotic therapy (ampicillin plus amikacin) should be considered for neonates who develop clinical sepsis within 48–72 h of birth and experience respiratory failure at birth. Full article

(This article belongs to the Special Issue Optimizing Antimicrobial Therapy in NICU Settings: Strategies and Implications)

26 pages, 1874 KiB

Open AccessArticle

Antifungal Agents’ Trends of Utilization, Spending, and Prices in the US Medicaid Programs: 2009–2023

by Abdulrahman A. Alsuhibani, Norah A. Alobaid, Manar H. Alahmadi, Jood S. Alqannas, Wejdan S. Alfreaj, Rana F. Albadrani, Khalid A. Alamer, Yasser S. Almogbel, Ali Alhomaidan and Jeff J. Guo

Antibiotics 2025, 14(5), 518; https://doi.org/10.3390/antibiotics14050518 - 16 May 2025

Abstract

Background: Fungal infections, particularly among immunocompromised individuals, present significant challenges due to rising incidence rates, treatment costs, and increasing resistance to antifungal agents. This study evaluates trends in antifungal use among Medicaid beneficiaries, focusing on prescribing patterns, costs, and pricing to optimize therapy. [...] Read more.

Background: Fungal infections, particularly among immunocompromised individuals, present significant challenges due to rising incidence rates, treatment costs, and increasing resistance to antifungal agents. This study evaluates trends in antifungal use among Medicaid beneficiaries, focusing on prescribing patterns, costs, and pricing to optimize therapy. Methods: Using the national Medicaid outpatient pharmacy claims data collected by the US Center of Medicare and Medicaid Services, a retrospective drug utilization analysis was conducted for antifungal medications from 2009 to 2023. Antifungal medications were categorized based on therapeutic use. The study examined annual utilization, reimbursement, and pricing trends, along with the market share. Results: Overall Medicaid utilization of superficial fungal infections’ (SFIs’) medications increased from 3.95 million prescriptions in 2009 to 6.16 million in 2023. Nystatin was the most frequently utilized SFI agent, while fluconazole emerged as the most commonly prescribed agent for invasive fungal infections (IFIs). In 2022, a notable spike occurred in the number of prescriptions for both SFIs and IFIs. Medicaid’s total expenditure on SFI medications rose from USD 121.9 million in 2009 to USD 155 million in 2023, while spending on IFI medications fluctuated substantially, peaking at USD 156.8 million in 2022 before declining to USD 80.7 million in 2023. After being introduced to the market, efinaconazole became the most expensive SFI agent over the years. Isavuconazole, the latest approved IFI medication, demonstrated sustained utilization, reimbursement, and price increases. Conclusions: The substantial rise in antifungal utilization and spending underscores the growing financial burden on Medicaid, emphasizing the need for policy interventions to manage costs and generic drug substitution while ensuring equitable access to these essential treatments. However, this study is limited by the lack of clinical outcome data and information on off-label use. Additionally, reimbursement data may not accurately reflect actual drug prices. Full article

15 pages, 1185 KiB

Open AccessArticle

LC-MS/MS Determination of Quorum Sensing Molecules in Plasma from Burn Patients with Septic Shock Sustained by Acinetobacter Baumannii

by Nicolò Carpenito, Marta Leporati, Alberto Sciarrillo, Anna Pensa, Roberto Gambino, Giovanni Musso, Alberto Mella, Luigi Biancone, Daniela Risso, Filippo Mariano and Domenico Cosseddu

Antibiotics 2025, 14(5), 517; https://doi.org/10.3390/antibiotics14050517 - 16 May 2025

Abstract

Background/Objectives: Quorum Sensing (QS) refers to the communication mechanism in bacterial cells, which occurs through the production and detection of small signaling molecules to coordinate activities and monitor population size. In Gram-negative bacteria, QS is typically mediated by N-acyl-homoserine lactones (HSLs) and [...] Read more.

Background/Objectives: Quorum Sensing (QS) refers to the communication mechanism in bacterial cells, which occurs through the production and detection of small signaling molecules to coordinate activities and monitor population size. In Gram-negative bacteria, QS is typically mediated by N-acyl-homoserine lactones (HSLs) and 2-alkyl-4(1H)-quinolone metabolites (AQ). The present study aims to develop and validate an LC-MS/MS method for detecting QS molecules and apply it to the analysis of plasma samples from burn patients with septic shock caused by Acinetobacter baumannii. Methods: The LC-MS/MS method was developed and fully validated for the quantitative, simultaneous determination of five HSLs and four AQ molecules, ultimately derived from the plasma of three patients with septic shock, with samples collected over three consecutive days. Results: The developed method proved to be both specific and selective, demonstrating a good fit and linearity over the entire range of interest. Trueness and accuracy were satisfactory. The method showed excellent intra-assay precision (CV% was lower than 15%) and limits of quantification (LOQ) ranging from 0.02 to 0.79 ng/mL. In the patients’ samples, the concentration of 3-OH-C12-HSL peaked at 1.5 ng/mL on the first day, and C7-PQS, C9-PQS, HHQ, and HQNO ranged from 0.5 to 1.5 ng/mL, peaking at 5 ng/mL in one patient on the third day. Conclusions: A method for the simultaneous determination of nine QS molecules by LC-MS/MS was developed and validated. When applied, it showed good performance for the analysis of plasma samples and could be a useful tool for an improvement in the diagnosis, prognosis, or treatment monitoring of infections in burn patients caused by Acinetobacter baumannii. Full article

(This article belongs to the Special Issue Editorial Board Members’ Collection Series: New Strategies to Overcome Antibiotic Resistance)

► Show Figures

Figure 1

20 pages, 3248 KiB

Open AccessReview

The Antimicrobial Efficacy of Copper Complexes: A Review

by Kwanele Ngece, Vuyolwethu Khwaza, Athandwa M. Paca and Blessing A. Aderibigbe

Antibiotics 2025, 14(5), 516; https://doi.org/10.3390/antibiotics14050516 - 16 May 2025

Abstract

The alarming increase in antimicrobial resistance has intensified the search for novel therapeutic agents capable of combating resistant microbial strains. Copper complexes have emerged as promising antimicrobial agents due to their intrinsic redox activity, ability to disrupt microbial membranes, and interactions with vital [...] Read more.

The alarming increase in antimicrobial resistance has intensified the search for novel therapeutic agents capable of combating resistant microbial strains. Copper complexes have emerged as promising antimicrobial agents due to their intrinsic redox activity, ability to disrupt microbial membranes, and interactions with vital biomolecules such as DNA and proteins. This review critically evaluates the antimicrobial potential of copper complexes reported between 2018 and 2025, emphasizing their structural diversity, mechanisms of action, and biological performance against a wide range of bacterial and fungal pathogens. Key findings reveal that Schiff base copper complexes, amino acid derivatives, heterocyclic ligands, and mixed-ligand systems exhibit potent antimicrobial activities, often surpassing standard antibiotics. Mechanistically, copper complexes induce reactive oxygen species (ROS) generation, inhibit enzyme function, cause DNA cleavage, and compromise cell membrane integrity. Furthermore, structure–activity relationship (SAR) analyses indicate that ligand type, coordination geometry, and lipophilicity significantly influence antimicrobial efficacy. Overall, the reviewed studies support the development of copper-based compounds as viable candidates for antimicrobial drug development. This review also identifies current challenges and gaps in knowledge, such as limited in vivo studies and toxicity assessments, which must be addressed to advance these compounds toward clinical application. Full article

(This article belongs to the Special Issue Metal-Based Complexes as Novel Antimicrobial Strategies)

► Show Figures

Figure 1

7 pages, 193 KiB

Open AccessBrief Report

In Vitro Activity of Nisin A Against Staphylococci Isolated from Periprosthetic Joint Infection

by Melissa J. Karau, Christina A. Koscianski, Andrew D. Badley, Nicholas A. Bedard, John W. Zinckgraf and Robin Patel

Antibiotics 2025, 14(5), 515; https://doi.org/10.3390/antibiotics14050515 - 16 May 2025

Abstract

Background/Objectives: Staphylococci are the most common causes of periprosthetic joint infection (PJI); new antimicrobials are needed to manage these difficult infections. Nisin A is a lantibiotic peptide derived from Lactococcus lactis that has antimicrobial activity against Gram-positive bacteria, including staphylococci, and is [...] Read more.

Background/Objectives: Staphylococci are the most common causes of periprosthetic joint infection (PJI); new antimicrobials are needed to manage these difficult infections. Nisin A is a lantibiotic peptide derived from Lactococcus lactis that has antimicrobial activity against Gram-positive bacteria, including staphylococci, and is an FDA-approved preservative used in the food and dairy industry. Here, the in vitro nisin A susceptibility of PJI-associated staphylococci was assessed. Methods: The minimum inhibitory concentrations (MICs), minimum biofilm inhibitory concentrations (MBICs), and minimum biofilm bactericidal concentrations (MBBCs) of nisin A were measured by broth microdilution against 106 staphylococcus isolates isolated from PJI. MICs were assessed using 5 × 10⁵ CFU/mL plus nisin A. For MBICs, biofilms were grown on pegged lids for 6 h, followed by 20 h of treatment. For MBBCs, pegged lids were transferred to plates containing media only for 20 h. The results were determined as the lowest concentrations with no visual growth. Two-dimensional MICs with nisin A and vancomycin were assessed for 20 isolates. Fractional inhibitory concentrations (FICs) were calculated to determine synergistic, additive, antagonistic, or indifferent interactions. Results: The MIC that inhibited 90% of S. aureus and S. epidermidis was 4 µg/mL, apart from for the MRSA subset (8 µg/mL). The MBIC that inhibited 90% of isolates was 4 µg/mL. The MBBCs ranged from 4 to 256 µg/mL. When tested together, nisin A and vancomycin yielded an FIC between 1.25 and 1.5, indicative of indifference, except for one isolate each of MRSA and MSSA, for which an additive effect (FIC of 1) was observed. Conclusions: Nisin A showed inhibitory activity against staphylococci that cause PJI. Full article

(This article belongs to the Special Issue Antimicrobial Activity of Bioactive Peptides and Their Derivatives)

► Show Figures

Graphical abstract

3 pages, 143 KiB

Open AccessEditorial

Antimicrobial Resistance and Hospital- and Community-Associated Infections

by Samantha Flores-Treviño

Antibiotics 2025, 14(5), 514; https://doi.org/10.3390/antibiotics14050514 - 16 May 2025

Abstract

Antimicrobial resistance (AMR) poses a significant global threat to human health, and was estimated to be associated with almost one million deaths in 2019 [...] Full article

(This article belongs to the Special Issue Antimicrobial Resistance and Hospital- and Community-Associated Infections)

16 pages, 1064 KiB

Open AccessArticle

Social Determinants of Health and Antibiotic Consumption

by Yuliya Semenova, Kamila Akhmetova, Daniil Semenov, Larissa Makalkina, Vladimir Surov, Lyudmila Pivina, Assiya Turgambayeva, Tatiana Belikhina, Saule Maukayeva, Maya Goremykina and Praveen Kumar

Antibiotics 2025, 14(5), 513; https://doi.org/10.3390/antibiotics14050513 - 15 May 2025

Abstract

Background/Objectives: This study aims to analyze antibiotic consumption trends from 2014 to 2023 in Kazakhstan, Kyrgyzstan, Tajikistan, and Russia; forecast future trends up to 2030; and identify key social and economic factors influencing antibiotic use. Methods: Data on antibiotic consumption were [...] Read more.

Background/Objectives: This study aims to analyze antibiotic consumption trends from 2014 to 2023 in Kazakhstan, Kyrgyzstan, Tajikistan, and Russia; forecast future trends up to 2030; and identify key social and economic factors influencing antibiotic use. Methods: Data on antibiotic consumption were obtained from the World Health Organization Regional Office for Europe Antimicrobial Consumption Network. Social and economic indicators were sourced from the World Bank DataBank. Of the 86 factors initially considered, 35 were included in the analyses. The forecast modeling of antibiotic consumption trends until 2030 and linear regression analysis to assess associations between antibiotic consumption and its predictors were conducted via SPSS. Results: The lowest antibiotic consumption rates were observed in Kazakhstan and Russia, whereas Kyrgyzstan and Tajikistan presented higher rates. The projected antibiotic consumption rates are expected to decline only in Kazakhstan, with other countries remaining stable. Birth and death rates, as well as under-five mortality rates, were significant determinants of antibiotic consumption in Kazakhstan and Tajikistan. In Russia, per capita GDP was a key determinant, whereas in Kazakhstan, inflation in consumer prices played a significant role. Additionally, cereal production was significantly associated with antibiotic consumption in Kazakhstan. In Kyrgyzstan and Russia, measles immunization rates were important determinants, whereas in Kyrgyzstan, access to clean fuels and technologies for cooking was significantly associated with antibiotic consumption. Conclusions: The findings of this study provide valuable insights for strengthening antimicrobial stewardship programs by addressing key social and economic determinants of antibiotic use. Full article

► Show Figures

Figure 1

19 pages, 532 KiB

Open AccessArticle

Conventional Antimicrobial and Medicinal Plants from a Traditional Medicine Market in South Africa: An Interactive Antimicrobial and Toxicity Study

by Zelna Booth, Sabiha Essack and Sandy van Vuuren

Antibiotics 2025, 14(5), 512; https://doi.org/10.3390/antibiotics14050512 - 15 May 2025

Abstract

Background: The World Health Organization (WHO) has proposed the use of integrative medicine to achieve extended healthcare coverage in developing countries facing high morbidity. Traditional remedies are frequently employed to prevent and treat infections among South Africans; however, the ways in which they [...] Read more.

Background: The World Health Organization (WHO) has proposed the use of integrative medicine to achieve extended healthcare coverage in developing countries facing high morbidity. Traditional remedies are frequently employed to prevent and treat infections among South Africans; however, the ways in which they interact with conventional antimicrobials are largely unknown. Therefore, this study aimed to explore the interactions between commonly traded medicinal plants at a traditional medicine market in KwaZulu-Natal (KZN), South Africa, and conventional antibiotics and antifungals. Methods: To determine the interactive antimicrobial profiles for plant/conventional antimicrobial combinations, minimum inhibitory concentration (MIC) assays were performed against ESKAPE pathogens and the yeasts Candida albicans and Candida glabrata. Calculated fractional inhibitory concentration (ΣFIC) values were used to identify synergism or antagonism, with synergistic interactions further tested in vitro for toxicity. Results: A total of 952 combinations were tested, of which 5.8% and 54.6% of the plant/antibiotic combinations were synergistic and antagonistic, respectively; additionally, 1.7% and 58.6% of the plant/antifungal combinations showed synergism or antagonism, respectively. The most toxic plant/antibiotic combination was Artemisia afra with doxycycline (71.1% mortality). The most toxic plant/antifungal combination was Acorus calamus with fluconazole (78.8% mortality). Conclusions: When medicinal plants acquired from a traditional medicine market in South Africa are used in combination with conventional antibiotics and antifungals, more than half of the combinations exhibit antagonism, which is concerning. Full article

(This article belongs to the Special Issue Advancements in the Control and Diagnosis of Antimicrobial Resistance in Infectious Diseases)

► Show Figures

Graphical abstract

18 pages, 2265 KiB

Open AccessArticle

Pathogenomic Characterization of Multidrug-Resistant Escherichia coli Strains Carrying Wide Efflux-Associated and Virulence Genes from the Dairy Farm Environment in Xinjiang, China

by Muhammad Shoaib, Sehrish Gul, Sana Majeed, Zhuolin He, Baocheng Hao, Minjia Tang, Xunjing Zhang, Zhongyong Wu, Shengyi Wang and Wanxia Pu

Antibiotics 2025, 14(5), 511; https://doi.org/10.3390/antibiotics14050511 - 15 May 2025

Abstract

Background/Objectives: Livestock species, particularly dairy animals, can serve as important reservoirs of E. coli, carrying antibiotic resistance and virulence genes under constant selective pressure and their spread in the environment. In this study, we performed the pathogenomic analysis of seven multidrug [...] Read more.

Background/Objectives: Livestock species, particularly dairy animals, can serve as important reservoirs of E. coli, carrying antibiotic resistance and virulence genes under constant selective pressure and their spread in the environment. In this study, we performed the pathogenomic analysis of seven multidrug resistant (MDR) E. coli strains carrying efflux-associated and virulence genes from the dairy farm environment in Xinjiang Province, China. Methods: First, we processed the samples using standard microbiological techniques followed by species identification with MALDI-TOF MS. Then, we performed whole genome sequencing (WGS) on the Illumina NovaSeq PE150 platform and conducted pathogenomic analysis using multiple bioinformatics tools. Results: WGS analysis revealed that the E. coli strains harbored diverse antibiotic efflux-associated genes, including conferring resistance to fluoroquinolones, aminoglycosides, aminocoumarins, macrolides, peptides, phosphonic acid, nitroimidazole, tetracyclines, disinfectants/antiseptics, and multidrug resistance. The phylogenetic analysis classified seven E. coli strains into B1 (n = 4), C (n = 2), and F (n = 1) phylogroups. PathogenFinder predicted all E. coli strains as potential human pathogens belonging to distinct serotypes and carrying broad virulence genes (ranging from 12 to 27), including the Shiga toxin-producing gene (stx1, n = 1). However, we found that a few of the virulence genes were associated with prophages and genomic islands in the E. coli strains. Moreover, all E. coli strains carried a diverse bacterial secretion systems and biofilm-associated genes. Conclusions: The present study highlights the need for large-scale genomic surveillance of antibiotic-resistant bacteria in dairy farm environments to identify AMR reservoir spillover and pathogenic risks to humans and design targeted interventions to further stop their spread under a One Health framework. Full article

(This article belongs to the Special Issue Antibiotic Resistance: A One-Health Approach, 2nd Edition)

► Show Figures

Figure 1

26 pages, 1732 KiB

Open AccessArticle

Exploring the Antibacterial Potency of Cymbopogon Essential Oils: Liposome Encapsulation and Phytochemical Insights

by Abdirahman Elmi, Fatouma M. Abdoul-Latif, Andréea Pasc, Arnaud Risler, Stéphanie Philippot, Ricardo Gil-Ortiz, Dominique Laurain-Mattar and Rosella Spina

Antibiotics 2025, 14(5), 510; https://doi.org/10.3390/antibiotics14050510 - 15 May 2025

Abstract

Background: Antimicrobial resistance (AMR) represents a critical global health challenge, requiring innovative strategies to combat resistant bacterial strains. Cymbopogon essential oils (EOs) are promising natural antimicrobial agents. Methods: The EO of Cymbopogon commutatus was extracted by hydrodistillation from fresh aerial parts [...] Read more.

Background: Antimicrobial resistance (AMR) represents a critical global health challenge, requiring innovative strategies to combat resistant bacterial strains. Cymbopogon essential oils (EOs) are promising natural antimicrobial agents. Methods: The EO of Cymbopogon commutatus was extracted by hydrodistillation from fresh aerial parts and compared to commercial EOs from C. citratus, C. nardus, and C. winterianus. Antibacterial activity was evaluated against seven bacterial strains (two Gram-positive and five Gram-negative). Both water-soluble fractions and liposome-encapsulated formulations were tested. Liposomes were prepared using soybean lecithin, and their stability was assessed by dynamic light scattering (DLS). The chemical composition of the pure EOs, water-soluble fractions and non-water-soluble fractions was analyzed by gas chromatography–mass spectrometry (GC-MS). Results: Liposome encapsulation improved EO solubility in aqueous media and significantly enhanced antibacterial efficacy, reducing minimum inhibitory concentration (MIC) values compared to the water-soluble fractions (MICs ≥ 25%). Among the tested formulations, the liposome containing C. citratus EO exhibited the strongest inhibitory effect against Staphylococcus aureus (MIC: 0.04%) followed by liposomes with C. nardus and C. commutatus (MIC: 0.08%). Against Enterococcus faecalis, the most effective formulation was the liposome containing C. winterianus EO (MIC: 0.02%), followed by C. citratus (MIC: 0.08%). The liposome formulated with C. winterianus maintained its particle size over 72 h without phase separation. GC-MS analysis revealed distinct phytochemical profiles: C. commutatus EO was rich in piperitone (73.9%) and C. citratus was rich in (Z)-(3,3-Dimethyl)-cyclohexylideneacetaldehyde (39.9%) and citral (32.5%), while C. nardus and C. winterianus were dominated by geraniol (21.5%) and citronellal (30.8%), respectively. Notably, piperitone, the major compound in C. commutatus EO, exhibited strong antibacterial activity against S. aureus (MIC of <0.04%). Conclusions: These findings support the potential of liposome-encapsulated Cymbopogon EOs as an effective and sustainable strategy to address AMR. This study provides a foundation for the development of plant-based antimicrobial formulations with improved efficacy. Full article

(This article belongs to the Special Issue Essential Oil of the Plants: Chemical Composition, Antimicrobial Activity, and Biological Applications)

► Show Figures

Figure 1

11 pages, 1689 KiB

Open AccessArticle

Accurate Diagnosis of Pseudomonas aeruginosa Is Critical to Mitigating Development of Antibiotic Resistance

by Hala I. Al-Daghistani, Lubna F. Abu-Niaaj and Sima Zein

Antibiotics 2025, 14(5), 509; https://doi.org/10.3390/antibiotics14050509 - 15 May 2025

Abstract

Background: The accurate and rapid diagnosis of infections is critical for effective and timely treatment. Misdiagnosis often leads to the prescription of antibiotics not targeting the causing agent of infection and thus be the possible development of multidrug resistance. This collectively worsens [...] Read more.

Background: The accurate and rapid diagnosis of infections is critical for effective and timely treatment. Misdiagnosis often leads to the prescription of antibiotics not targeting the causing agent of infection and thus be the possible development of multidrug resistance. This collectively worsens the condition and might lead to unnecessary intervention or death. The abundance of Pseudomonas spp. in healthcare-settings and the environment may lead to the inaccurate diagnosis of P. aeruginosa, making the treatment of its infections challenging. P. aeruginosa is a Gram-negative, opportunistic pathogen commonly linked to healthcare-associated infections. Its pathogenicity is attributed to several virulence factors correlated to enhanced survivability and colonization, invasion of the host tissues, and the development of multidrug resistance. When advanced diagnostic facilities are limited or unaffordable, the prescription of antibiotics solely relies on identifying the bacteria by culture-based methods. Objectives: This study aims to validate the accuracy of diagnosis of fifty clinical isolates preidentified as P. aeruginosa in three healthcare facilities in Jordan. Methods: The isolates were from infected areas of patients, including skin, wounds, ears, urine, and peritoneal cavities. Morphological and biochemical tests were performed, and the validation relied on the polymerase chain reaction (PCR) amplification of the 16S ribosomal ribonucleic acid (rRNA) gene. This molecular method is affordable for medical facilities with limited finances in contrast to advanced high-cost techniques. Results: The PCR confirmed that only 60% of the isolates were P. aeruginosa. All the confirmed isolates could produce different pigments and form biofilms. Conclusions: The high percentage of isolates mistakenly identified as P. aeruginosa raises concern about the suitability of prescribed antibiotics. The present study strongly recommends using advanced molecular methods to identify the pathogens. If conventional methods remain the only diagnostic option, this study recommends frequent external validation for tests in addition to performing an antibiotic susceptibility test to pinpoint the effective antibiotics against biofilm-producing P. aeruginosa. Full article

(This article belongs to the Special Issue Preventing Antimicrobial Resistance in Hospitals: Infection Control and Antibiotic Use)

► Show Figures

Figure 1

12 pages, 2438 KiB

Open AccessArticle

High-Dose Ceftriaxone in Elderly Patients with Enterococcal Infective Endocarditis: Population Pharmacokinetics of Free Ceftriaxone and Dose Optimization

by Beatriz Fernández Rubio, Fernando Docobo Pérez, Laura Herrera Hidalgo, Luis Eduardo López-Cortés, Rafael Luque Márquez, José Manuel Lomas Cabezas, Luis Fernando López-Cortés, Marta Mejías Trueba, Ana Belén Guisado Gil, Alicia Gutiérrez Valencia, Arístides de Alarcón González and María Victoria Gil Navarro

Antibiotics 2025, 14(5), 508; https://doi.org/10.3390/antibiotics14050508 - 15 May 2025

Abstract

Background: Ampicillin plus ceftriaxone (AC) is a first-line treatment for Enterococcus faecalis infective endocarditis (IE). Its administration in outpatient parenteral antibiotic treatment (OPAT) programs is challenging. The design of a ceftriaxone regimen suitable for OPAT requires deep knowledge of ceftriaxone pharmacokinetics (PK). Objective: [...] Read more.

Background: Ampicillin plus ceftriaxone (AC) is a first-line treatment for Enterococcus faecalis infective endocarditis (IE). Its administration in outpatient parenteral antibiotic treatment (OPAT) programs is challenging. The design of a ceftriaxone regimen suitable for OPAT requires deep knowledge of ceftriaxone pharmacokinetics (PK). Objective: We aim to explore ceftriaxone PK in elderly patients and propose dose regimens adapted to OPAT to maintain synergistic concentrations (Cs) with ampicillin against E. faecalis. Methods: We conducted a prospective observational pharmacokinetic study on patients (>55 years old) affected by E. faecalis IE. Ceftriaxone free concentration was measured at three time-points: before the administration (C_min) and two and four hours after ceftriaxone administration (C₂ and C₄). Both structural and covariate population pharmacokinetic models were built. Monte Carlo simulations of six ceftriaxone dosages were performed and the probability of target attainment (PTA) of an optimal Cs range was analyzed. The pharmacokinetic/pharmacodynamic index (PK/PD) to predict efficacy was defined as maintaining free ceftriaxone concentrations superior to the Cs at 50–100% of the dosing interval (fT ≥ Cs ≥ 50–100% of the dosing interval). Ceftriaxone dosing regimens were considered optimal if at least 90% of the simulated population was able to achieve the defined PK/PD targets. Results: Twenty-four episodes from 16 patients were included. Mean free ceftriaxone concentration pre-dose, +2 h, and +4 h were C_min = 7.8 ± 6.5 mg/L, C₂ = 34 ± 26.5 mg/L, and C₄ = 22.7 ± 19.7 mg/L, respectively. A two-compartment model with first-order absorption and elimination best described the data. Ceftriaxone one-hour infusions only achieved the minimum PK/PD target when the 2 g/12 h regimen was tested. On the other hand, ceftriaxone continuous infusion maintained a Cs above the PK/PD target for 100% of the dosing interval using ceftriaxone 4–6 g regimens. Conclusions: Our findings suggest that the optimal ceftriaxone exposure may be achieved using high-dose continuous infusions to ensure an ampicillin-killing effect when treating E. faecalis IE. Full article

(This article belongs to the Section Pharmacokinetics and Pharmacodynamics of Drugs)

► Show Figures

Figure 1

22 pages, 4238 KiB

Open AccessArticle

Surviving Colonies of Pseudomonas aeruginosa Isolated In Vivo from Infected, Antibiotic-Treated Galleria mellonella Larvae Acquire an Antibiotic-Tolerant Phenotype

by Alex McCormack, Joanne K. Hobbs, Paul R. Johnston and Peter J. Coote

Antibiotics 2025, 14(5), 507; https://doi.org/10.3390/antibiotics14050507 - 15 May 2025

Abstract

Background: The aim of this work was to induce the formation of antibiotic-tolerant and/or persister cells in vivo using antibiotic therapy on Galleria mellonella larvae infected with P. aeruginosa, isolate these surviving cells, and characterise their phenotype and genotype. Methods: Infected [...] Read more.

Background: The aim of this work was to induce the formation of antibiotic-tolerant and/or persister cells in vivo using antibiotic therapy on Galleria mellonella larvae infected with P. aeruginosa, isolate these surviving cells, and characterise their phenotype and genotype. Methods: Infected larvae were treated with effective doses of either ceftazidime or meropenem. Despite this, surviving P. aeruginosa colonies were isolated from living larvae, and antibiotic killing, fitness, virulence, antibiotic resistance and the whole genome sequence of a selection of these isolates were compared with their original parent strains. Results: The surviving isolates had an increased minimum duration to kill 99% of the population (MDK₉₉) upon exposure to ceftazidime or meropenem and decreased growth rates in culture, but they showed no change to the MIC or virulence—consistent with an antibiotic-tolerant phenotype. Long-read genome sequencing of selected isolates revealed only one single nucleotide polymorphism (SNP) within bkdB, encoding the lipoamide acyltransferase component of the branched-chain α-keto acid dehydrogenase, present in two independent isolates. However, time-kill assays with ceftazidime of bkdB knockout strains showed no significant change in the MDK₉₉. Concomitant with the antibiotic-tolerant phenotype, many of the isolates also had a reduced rate of killing when exposed to heat stress. Conclusions: P. aeruginosa cells that survived antibiotic therapy in vivo were found to be antibiotic-tolerant and thermotolerant but not antibiotic-resistant and had reduced growth rates under optimal conditions but unchanged virulence. In the absence of a convincing genetic explanation, the co-induction of enhanced thermotolerance with antibiotic tolerance indicated that both are conferred by a heritable phenotypic mechanism. Full article

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

► Show Figures

Figure 1

23 pages, 432 KiB

Open AccessReview

One Health at Risk: Plasmid-Mediated Spread of mcr-1 Across Clinical, Agricultural, and Environmental Ecosystems

by Abdelaziz Touati, Nasir Adam Ibrahim, Assia Mairi, Hassina Kirat, Nosiba S. Basher and Takfarinas Idres

Antibiotics 2025, 14(5), 506; https://doi.org/10.3390/antibiotics14050506 - 15 May 2025

Abstract

The global dissemination of plasmid-mediated mcr genes, which confer resistance to the last-resort antibiotic colistin, represents a critical public health challenge driven by the interplay of clinical, agricultural, and environmental factors. This review examines the genetic and ecological dynamics of mcr-bearing plasmids, [...] Read more.

The global dissemination of plasmid-mediated mcr genes, which confer resistance to the last-resort antibiotic colistin, represents a critical public health challenge driven by the interplay of clinical, agricultural, and environmental factors. This review examines the genetic and ecological dynamics of mcr-bearing plasmids, focusing on their role in disseminating colistin resistance across diverse bacterial hosts and ecosystems. Key plasmid families demonstrate distinct evolutionary strategies, including IncI2, IncHI2, and IncX4. IncI2 plasmids favor stability in livestock and clinical settings. IncHI2 plasmids, on the other hand, leverage transposons to co-select for multidrug resistance, while IncX4 plasmids achieve global dissemination through streamlined, conjugation-efficient architectures. The pervasive spread of mcr genes is exacerbated by their integration into chromosomes via mobile genetic elements and co-selection with resistance to other antibiotic classes, amplifying multidrug-resistant phenotypes. Environmental reservoirs, food chains, and anthropogenic practices further facilitate cross-niche transmission, underscoring the interconnectedness of resistance under the One Health framework. Addressing this crisis requires coordinated strategies, including reducing colistin misuse in agriculture, enhancing surveillance of high-risk plasmid types, and fostering international collaboration to preserve antimicrobial efficacy and mitigate the threat of untreatable infections. Full article

(This article belongs to the Special Issue A One Health Approach to Antimicrobial Resistance, 2nd Edition)

14 pages, 2616 KiB

Open AccessArticle

Determination of Colistin Resistance in Clinical Isolates from Healthcare Facilities in Mthatha and Surrounding Areas

by Silindokuhle Ndlela, Ravesh Singh and Sandeep Vasaikar

Antibiotics 2025, 14(5), 505; https://doi.org/10.3390/antibiotics14050505 - 14 May 2025

Abstract

Background: Antimicrobial resistance (AMR) is a global threat in the public healthcare sector. The emergence of carbapenem-resistant Enterobacterales (CRE) has become a serious public health threat in South Africa. The spread of CRE has led to the use of colistin for treating [...] Read more.

Background: Antimicrobial resistance (AMR) is a global threat in the public healthcare sector. The emergence of carbapenem-resistant Enterobacterales (CRE) has become a serious public health threat in South Africa. The spread of CRE has led to the use of colistin for treating severe infections. Colistin is a cationic, lipopeptide antibacterial agent that is effective against most Gram-negative bacteria through its disruption of the bacterial cell membrane. This study aims to determine the colistin resistance (MIC) and mobile colistin resistance (mcr-1) gene in clinical isolates from healthcare facilities in Mthatha and its surrounding areas. Methods: Fifty-three CRE isolates were collected from health facilities between January 2019 and June 2021 and stored in skim milk 10% and 5% inositol broth. The carbapenemase confirmatory test involved a RESIST-4 O.K.N.V assay (Coris BioConcept, Gembloux, Belgium), which was conducted following manufacturer protocol. Broth microdilution was performed according to the ISO standard method (20776-1) using A ComAspTM colistin 0.25–16 μg/mL MIC Broth. Conventional polymerase reaction (PCR) was performed for the detection of mcr-1. Results: N = 53 (100%) isolates were used. A total of 53% were defined as Klebsiella pneumoniae, Escherichia coli constituted 8%, Enterobacter cloacae 8%, Serratia marcescens 8%, Serratia fonticola 2%, Enterobacter aerogenes 2%, Klebsiella oxytoca 2%, Citrobacter koseri 2%, and Citrobacter freundii 2%. The specimens were from the following wards: Pediatric and Neonatal 38%, Medical 30%, Gynecology, Labour, and Maternity 11%, OPD and A&E 11%, ENT 4%, and Others—Male TB ward, Trauma, and adult ICU 6%. In total, 13% of the isolates were resistant and 86% were sensitive to colistin. The common CRE genes detected were OXA-48 at 47%, NDM at 13%, VIM at 1%, and a combination of OXA-48 and NDM at 5%. Of the isolates, 66% were positive for the production of carbapenamase. In this study, we found that all N = 53 (100%) isolates did not have the mobile colistin resistance gene (mcr-1). Conclusions: Antimicrobial resistance is associated with the emergence of carbapenemases genes. Increasing resistance to colistin in clinical settings can lead to difficulties in treating CRE infections, which may lead to clinical failure. In our study, 13% of isolates were phenotypically resistant to colistin. Full article

(This article belongs to the Special Issue Infection and Treatment of Antibiotic-Resistant ESKAPE Pathogens)

► Show Figures

Figure 1

21 pages, 7339 KiB

Open AccessArticle

In Vitro Analysis of Interactions Between Staphylococcus aureus and Pseudomonas aeruginosa During Biofilm Formation

by Julia Scaffo, Rayssa Durães Lima, Cameron Dobrotka, Tainara A. N. Ribeiro, Renata F. A. Pereira, Daniela Sachs, Rosana B. R. Ferreira and Fabio Aguiar-Alves

Antibiotics 2025, 14(5), 504; https://doi.org/10.3390/antibiotics14050504 - 14 May 2025

Abstract

Staphylococcus aureus and Pseudomonas aeruginosa are classified as ESKAPE pathogens that present a significant challenge to treatment due to their increased resistance to a considerable number of antimicrobial agents. Background/Objective: Biofilms exacerbate treatment challenges by providing enhanced antimicrobial and environmental protection. Mixed-species [...] Read more.

Staphylococcus aureus and Pseudomonas aeruginosa are classified as ESKAPE pathogens that present a significant challenge to treatment due to their increased resistance to a considerable number of antimicrobial agents. Background/Objective: Biofilms exacerbate treatment challenges by providing enhanced antimicrobial and environmental protection. Mixed-species biofilms further complicate treatment options through numerous complex interspecies interactions, leading to potentially severe adverse clinical outcomes. Methods: This study assessed the interaction between clinical S. aureus and P. aeruginosa isolates during biofilm formation using microplate biofilm formation assays, scanning electron microscopy, and confocal microscopy. Results: We identified a competitive relationship between P. aeruginosa and S. aureus, where both pathogens exhibited a reduction in biofilm formation during mixed-species biofilms compared with monocultures, although P. aeruginosa outcompeted S. aureus. Furthermore, we found that the cell-free conditioned media (CFCM) of P. aeruginosa significantly reduced the S. aureus biofilms. Using fractioned CFCM, we identified that the anti-staphylococcal activity of the >10 kDa fraction was almost identical to the non-fractioned CFCM. Our confocal microscopy results suggest that P. aeruginosa CFCM depolarize S. aureus membranes and reduces the biofilm burden. Conclusions: These findings contribute to our understanding of the mechanisms underlying the interactions between these pathogens, suggesting that there is an antagonistic relationship between S. aureus and P. aeruginosa in a biofilm setting. Full article

(This article belongs to the Special Issue Antimicrobial Resistance in Biofilm-Associated Infections)

► Show Figures

Figure 1

34 pages, 708 KiB

Open AccessReview

Essential Oils for Biofilm Control: Mechanisms, Synergies, and Translational Challenges in the Era of Antimicrobial Resistance

by Abdelaziz Touati, Assia Mairi, Nasir Adam Ibrahim and Takfarinas Idres

Antibiotics 2025, 14(5), 503; https://doi.org/10.3390/antibiotics14050503 - 13 May 2025

Abstract

Biofilms, structured microbial consortia embedded in self-produced extracellular matrices, pose significant challenges across the medical, industrial, and environmental sectors due to their resistance to antimicrobial therapies and ability to evade the immune system. Their resilience is driven by multifaceted mechanisms, including matrix-mediated drug [...] Read more.

Biofilms, structured microbial consortia embedded in self-produced extracellular matrices, pose significant challenges across the medical, industrial, and environmental sectors due to their resistance to antimicrobial therapies and ability to evade the immune system. Their resilience is driven by multifaceted mechanisms, including matrix-mediated drug sequestration, metabolic dormancy, and quorum sensing (QS)-regulated virulence, which collectively sustain persistent infections and contribute to the amplification of antimicrobial resistance (AMR). This review critically examines the potential of plant-derived essential oils (EOs) as innovative agents for biofilm control. EOs exhibit broad-spectrum antibiofilm activity through multi-target mechanisms, including disrupting initial microbial adhesion, degrading extracellular polymeric substances (EPSs), suppressing QS pathways, and compromising membrane integrity. Their ability to act synergistically with conventional antimicrobials at sub-inhibitory concentrations enhances therapeutic efficacy while reducing the selection pressure for resistance. Despite their potential, EO applications face technical challenges, such as compositional variability due to botanical sources, formulation stability issues, and difficulties in standardization for large-scale production. Clinical translation is further complicated by biofilm stage- and strain-dependent efficacy, insufficient in vivo validation of therapeutic outcomes, and potential cytotoxicity at higher doses. These limitations underscore the need for optimized delivery systems, such as nanoencapsulation, to enhance bioavailability and mitigate adverse effects. Future strategies should include combinatorial approaches with antibiotics or EPS-degrading enzymes, advanced formulation technologies, and standardized protocols to bridge laboratory findings to clinical practice. By addressing these challenges, EOs hold transformative potential to mitigate biofilm-associated AMR, offering sustainable, multi-target alternatives for infection management and biofilm prevention in diverse contexts. Full article

(This article belongs to the Special Issue Essential Oil of the Plants: Chemical Composition, Antimicrobial Activity, and Biological Applications)

► Show Figures

Figure 1

25 pages, 1114 KiB

Open AccessArticle

Molecular Detection of Antibiotic Resistance Genes Using Respiratory Sample from Pneumonia Patients

by Eman Abdullah Alsuof, Ahmad R. Alsayed, Manar Saleh Zraikat, Heba A. Khader, Luai Z. Hasoun, Mamoon Zihlif, Osama Abu Ata, Malek A. Zihlif, Mahmoud Abu-Samak and Mohammed Al Maqbali

Antibiotics 2025, 14(5), 502; https://doi.org/10.3390/antibiotics14050502 - 13 May 2025

Abstract

Introduction/Objectives: Antibiotic resistance makes the treatment of pneumonia challenging. Effective management depends on accurate diagnostic techniques to identify resistance genes and customize drugs. This study primarily aimed to identify antibiotic resistance genes in respiratory samples from patients with pneumonia using polymerase chain reaction [...] Read more.

Introduction/Objectives: Antibiotic resistance makes the treatment of pneumonia challenging. Effective management depends on accurate diagnostic techniques to identify resistance genes and customize drugs. This study primarily aimed to identify antibiotic resistance genes in respiratory samples from patients with pneumonia using polymerase chain reaction (PCR) to determine the prevalence of specific resistance genes and analyze clinical factors contributing to antibiotic resistance, as well as to provide actionable insights into resistance patterns in Jordan and support efforts to improve pneumonia management. Methods: This retrospective observational study included 114 patients who were diagnosed with pneumonia. Clinical data, including prior antibiotic exposure and treatment history, were collected. PCR diagnostics were used to detect resistance genes in respiratory samples. In this study, we evaluated 14 antibiotic resistance genes in pneumonia pathogens, highlighting their diverse resistance mechanisms. Results: Mec A was the most frequently detected gene, appearing in 87 samples (77.3%). Additionally, Tem in 80 samples (70.2%), Oxa-48-like in 15 samples (13.2%), and Ctx-M-1 in 38 samples (33.3%) were among the most commonly detected genes. In contrast, Oxa-40-like (7.0%), Vim (8.8%), and Imp (4.4%) genes exhibited a lower prevalence. The Oxa-51-like gene showed the only significant association with ertapenem resistance (p-value = 0.046). Further analysis revealed statistically significant associations between Mec A and methicillin resistance (p < 0.001), underscoring its critical role. However, other genes, such as Oxa-40-like and Oxa-48-like, showed no significant correlation with the antibiotic resistance patterns of imipenem and meropenem (p > 0.05). Conclusions: This study demonstrates the utility of PCR-based diagnostics for detecting resistance genes and highlights the critical clinical factors associated with antibiotic resistance in patients with pneumonia. These findings underscore the importance of integrating molecular diagnostics into routine care to improve treatment outcomes and combat the growing threat of antibiotic resistance in Jordan. This highlights PCR’s value in guiding effective treatment strategies and addressing multidrug-resistant pneumonia. Full article

(This article belongs to the Special Issue Epidemiology and Mechanism of Bacterial Resistance to Antibiotics)

► Show Figures

Figure 1

Journal Description

Antibiotics

Latest Articles

Journal Menu

Journal Browser

Highly Accessed Articles

Latest Books

E-Mail Alert

News

Topics

Conferences

Special Issues

Topical Collections

Further Information

Guidelines

MDPI Initiatives

Follow MDPI