Antibiotics

24 pages, 1219 KiB

Open AccessArticle

Antibacterial and Synergistic Effects of Terminalia citrina Leaf Extracts Against Gastrointestinal Pathogens: Insights from Metabolomic Analysis

by Sze-Tieng Ang, Tak Hyun Kim, Matthew James Cheesman and Ian Edwin Cock

Antibiotics 2025, 14(6), 593; https://doi.org/10.3390/antibiotics14060593 (registering DOI) - 8 Jun 2025

Abstract

Background/Objectives: Bacterial contamination leads to foodborne illnesses, and new antibiotics are required to combat these pathogens. Interest has increased in medicinal plants as targets for new antibiotics. Methods: This study evaluated the antibacterial activity of leaf extracts from Terminalia citrina (Gaertn.) [...] Read more.

Background/Objectives: Bacterial contamination leads to foodborne illnesses, and new antibiotics are required to combat these pathogens. Interest has increased in medicinal plants as targets for new antibiotics. Methods: This study evaluated the antibacterial activity of leaf extracts from Terminalia citrina (Gaertn.) Roxb. ex Fleming against four bacterial pathogens (including a methicillin-resistant Staphylococcus aureus (MRSA) strain) using disc diffusion and liquid microdilution assays. The phytochemical composition of the extracts were determined using ultra-high-performance liquid chromatography–mass spectrometry (UPLC-MS). Results: Both the aqueous and methanol extracts demonstrated noteworthy antibacterial activity against Bacillus cereus (MICs of 468.8 µg/mL and 562.5 µg/mL, respectively). Additionally, the extracts were effective against MRSA (MICs = 625 µg/mL). Strong antibacterial effects were also observed against S. aureus, with MICs of 625 µg/mL (aqueous extract) and 833.3 µg/mL (methanol extract). Twelve combinations of extracts and conventional antibiotics were synergistic against B. cereus and S. flexneri. UPLC-MS analysis revealed two flavonoids, orientin 2″-O-gallate and astragalin, exclusive to the aqueous extract, whilst pinocembrin and gallic acid were only detected in the methanol extract. Both extracts contained vitexin 2″-O-p-coumarate, ellagic acid, orientin, rutin, chebulic acid, terminalin, and quercetin-3β-D-glucoside. Both extracts were determined to be nontoxic. Conclusions: The abundance and diversity of polyphenols in the extracts may contribute to their strong antibacterial properties. Further research is required to investigate the antibacterial effects of the individual extract compounds, including their effects when combined with conventional antibiotics, and the potential mechanisms of action against foodborne pathogens. Full article

(This article belongs to the Special Issue New Natural Products as Candidates for the Discovery of Antimicrobial Drugs)

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27 pages, 3028 KiB

Open AccessArticle

Integrated Assessment of Antibacterial Activity, Polyphenol Composition, Molecular Docking, and ADME Properties of Romanian Oak and Fir Honeydew Honeys

by Calin Hulea, Diana Obistioiu, Anca Hulea, Mukhtar Adeiza Suleiman, Doris Floares (Oarga), Ersilia Alexa, Ilinca Merima Imbrea, Alina-Georgeta Neacșu, Marius Pentea, Cosmin Alin Popescu and Florin Imbrea

Antibiotics 2025, 14(6), 592; https://doi.org/10.3390/antibiotics14060592 (registering DOI) - 8 Jun 2025

Abstract

Background: This study evaluated the polyphenolic composition, antibacterial activity, molecular docking interactions, and pharmacokinetic properties of Romanian oak and fir honeydew honeys. Methods: Spectrophotometric methods quantified total phenolic, flavonoid contents and antioxidant activity, and individual polyphenols were identified via HPLC-MS. Antibacterial efficacy against [...] Read more.

Background: This study evaluated the polyphenolic composition, antibacterial activity, molecular docking interactions, and pharmacokinetic properties of Romanian oak and fir honeydew honeys. Methods: Spectrophotometric methods quantified total phenolic, flavonoid contents and antioxidant activity, and individual polyphenols were identified via HPLC-MS. Antibacterial efficacy against Gram-positive and Gram-negative bacteria was evaluated by determining the bacterial inhibition percentage and minimum inhibitory concentrations. The bioactive compounds identified via LC-MS analysis were used to further delineate the possible antibacterial activities in silico. Molecular docking was carried out to predict the binding interactions and complex formation of the identified compounds against protein crystal structures of the bacteria used in this study. Additionally, the pharmacokinetic profile of compounds with high inhibitory potential was assessed via ADMET (absorption, Distribution, Metabolism, Excretion, toxicity) predictors to ascertain their value. Results: Fir honeydew honey showed higher total phenolic (844.5 mg GAE/kg) and flavonoid contents (489.01 mg QUE/kg) compared to oak honeydew honey, correlating with more potent antioxidant activity (IC50 = 5.16 mg/mL). In vitro antimicrobial tests indicated a stronger inhibitory effect of fir honeydew honey, especially against Gram-positive strains like S. aureus, S. pyogenes, and L. monocytogenes, alongside certain Gram-negative strains such as E. coli and H. influenzae. Oak honeydew honey displayed selective antimicrobial action, particularly against P. aeruginosa and S. typhimurium. The docking outcomes showed rutin, rosmarinic acid, beta resorcylic acid, quercetin, ferulic acid, and p-coumaric acid have high inhibitory activities characterised by binding affinities and binding interactions against shiga toxin, riboflavin synthase, ATP-binding sugar transporter-like protein, undecaprenyl diphosphate synthase, putative lipoprotein, sortase A, and immunity protein, making them key contributors to the honey’s antimicrobial activity. Moreover, beta-resorcylic acid, quercetin, ferulic acid, and p-coumaric acid revealed interesting ADMET scores that qualify honey to serve as a good antimicrobial agent. Conclusions: These findings support their potential use as natural antibacterial agents and emphasise the value of integrating chemical, biological, and computational approaches for multidisciplinary characterisations. Full article

(This article belongs to the Special Issue Antimicrobial Activities of Bioactive Components from Honeybee Products)

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16 pages, 856 KiB

Open AccessArticle

Novel p-Hydroxybenzoic Acid Derivative Isolated from Bacopa procumbens and Its Antibacterial Activity

by Elizabeth Vargas-Anaya, Alejandro Zamilpa, Manasés González-Cortazar, Blanca Eda Domínguez-Mendoza, Ma. Dolores Pérez-García, Minerva Rosas Morales, Ada María Ríos Cortés and Valentin López Gayou

Antibiotics 2025, 14(6), 591; https://doi.org/10.3390/antibiotics14060591 (registering DOI) - 7 Jun 2025

Abstract

Background/Objectives: Antimicrobial resistance represents a critical global health challenge that has been exacerbated by the significant decline in antibiotic development. Natural product-based drugs, particularly plant-derived phenolic compounds, offer promising alternatives to conventional antibiotics. This study aimed to isolate and characterize a novel phenolic [...] Read more.

Background/Objectives: Antimicrobial resistance represents a critical global health challenge that has been exacerbated by the significant decline in antibiotic development. Natural product-based drugs, particularly plant-derived phenolic compounds, offer promising alternatives to conventional antibiotics. This study aimed to isolate and characterize a novel phenolic compound from Bacopa procumbens, a Mexican perennial repent plant that is widespread in the Mexican valley and produces a variety of saponins, gastrodin derivatives, and phenolic acids, and to evaluate its antibacterial potential against clinically relevant pathogens. Methods: The hydroalcoholic extraction of B. procumbens was followed by liquid–liquid partitioning with ethyl acetate. The resulting fraction underwent chromatographic separation and purification. The structural elucidation of the isolated compound was performed using thin-layer chromatography (TLC), high-performance liquid chromatography (HPLC), mass spectrometry (MS-EI), and nuclear magnetic resonance (NMR) techniques. Antimicrobial activity was assessed via a microdilution assay against five bacterial strains, including drug-resistant Staphylococcus species and Gram-negative pathogens. Results: A novel phenolic compound, 5-(p-hydroxybenzoyl) shikimic acid (5pHSA), was isolated and characterized. The compound demonstrated moderate antibacterial activity against methicillin-resistant Staphylococcus haemolyticus and Escherichia coli (minimum inhibitory concentration (MIC) = 100 μg/mL) but showed limited efficacy against Staphylococcus aureus, MRSA, and Klebsiella pneumoniae (MIC > 100 μg/mL). Comparative analysis with the previously isolated compound ProcumGastrodin A revealed structure–activity relationships where the higher lipophilicity of PG-A was correlated with enhanced antimicrobial activity. Conclusions: This study establishes 5pHSA as a novel phenolic compound with moderate antibacterial properties. The findings highlight the importance of molecular polarity and structural complexity in determining antimicrobial efficacy, offering valuable insights into the development of phenolic, acid-based antimicrobial agents to address the growing challenge of antimicrobial resistance. Full article

(This article belongs to the Special Issue Antimicrobial Activity of Plants Against Emerging or Drug-Resistant Human Pathogens)

14 pages, 1495 KiB

Open AccessArticle

Assessment of Oral Microbial Viability by 2,6-Dichlorophenolindophenol a Redox Agent

by Prem K. Sreenivasan and Violet I. Haraszthy

Antibiotics 2025, 14(6), 590; https://doi.org/10.3390/antibiotics14060590 (registering DOI) - 7 Jun 2025

Abstract

Background/Objectives: This investigation evaluated 2,6-Dichlorophenolindophenol (DCIP), a redox dye, as a colorimetric reagent for rapid quantification of oral bacteria and examined the antimicrobial effects of oral hygiene formulations. Methods/Results: Viable microbial cells reduce DCIP, resulting in a loss of its blue color which [...] Read more.

Background/Objectives: This investigation evaluated 2,6-Dichlorophenolindophenol (DCIP), a redox dye, as a colorimetric reagent for rapid quantification of oral bacteria and examined the antimicrobial effects of oral hygiene formulations. Methods/Results: Viable microbial cells reduce DCIP, resulting in a loss of its blue color which can be measured spectrophotometrically. Strains of Actinomyces viscosus, Veillonella atypica, Aggregatibacter actinomycetemcomitans, Streptococcus mutans and Candida albicans grown in the laboratory reduced DCIP. Significant correlations between increasing viable plate counts and DCIP reduction were noted for strains of oral organisms. Intact microbial cells reduced DCIP, with insignificant reductions observed by spent microbial media or bacteria free culture media. Organisms inactivated by either heat or cold demonstrated significantly lower DCIP reduction in comparison to metabolically intact organisms grown under optimal conditions. Conclusions: DCIP reduction provided a rapid and accurate method to evaluate antimicrobial effects of clinical proven mouthwashes formulated with cetylpyridinium chloride or chlorhexidine and toothpastes for a range of oral bacteria. Together, these results identify a rapid, low-cost method using common laboratory equipment to enumerate oral organisms with a visual outcome. Full article

(This article belongs to the Special Issue Antibacterial Treatment in Periodontal and Endodontic Therapy, 3rd Edition)

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11 pages, 239 KiB

Open AccessBrief Report

Resistance Patterns of Neisseria gonorrhoeae in PLHIV: A Cross-Sectional Study from the Republic of Cyprus, 2015–2023

by Michaela Takos, George Siakallis, Annalisa Quattrocchi, Maria Alexandrou, Panagiota Papadamou, Loukia Panagiotou and Danny Alon-Ellenbogen

Antibiotics 2025, 14(6), 589; https://doi.org/10.3390/antibiotics14060589 (registering DOI) - 7 Jun 2025

Abstract

Background: The rise in antimicrobial-resistant (AMR) strains of Neisseria gonorrhoeae is internationally recognised as a critical public health concern, with limited treatment options available. The urgency of this issue prompted the European Centre for Disease Prevention and Control to establish ‘EURO-GASP’ to monitor [...] Read more.

Background: The rise in antimicrobial-resistant (AMR) strains of Neisseria gonorrhoeae is internationally recognised as a critical public health concern, with limited treatment options available. The urgency of this issue prompted the European Centre for Disease Prevention and Control to establish ‘EURO-GASP’ to monitor trends in resistance and address developments. Comprehensive data on AMR strains in people living with HIV (PLHIV) is limited, especially in Cyprus. Objectives: To analyse trends in rates of resistant N. gonorrhoeae infections and identify any correlations between patient factors that may contribute to such in PLHIV in The Republic of Cyprus. Methods: We conducted a retrospective chart review study on N. gonorrhoea resistance among PLHIV from the Gregorios HIV reference clinic in Larnaca, Cyprus, between 2015 and 2023. Antimicrobial susceptibility was assessed via disc diffusion or gradient strip method on GC II agar against a non-homogenous panel of antibiotic preparations, based on standard laboratory practice variation. Demographic and clinical data, including antibiograms, treatments and test of cure, were recorded. Statistical analysis was performed using Stata v16, with significance set at p < 0.05. The study received approval from the Cyprus National Bioethics Committee. Results: A total of 45 isolates from 39 patients were analysed, with 62% of these demonstrating resistance to at least one antibiotic. Resistance rates were not shown to change over time. We identified a statistically significant linear association between a person having a history of an STI and the number of antibiotics which the isolate is resistant to (β = 1.2; p: 0.004). Notably, a single isolate demonstrated resistance to ceftriaxone, the first-line treatment currently recommended in both Europe and the United States. This finding is particularly alarming given the critical role of ceftriaxone in the management of gonorrhoea. Conclusions: Whilst there has been no increase in resistance rates over time, the detection of ceftriaxone-resistant N. gonorrhoeae is a significant public health concern. Given that having a history of an STI makes a person more likely to develop a resistant infection, PLHIV or those who engage in risky sexual behaviours are particularly vulnerable. There is a pressing need to enhance surveillance and implement routine susceptibility testing in Cyprus, given the country’s role as a major international hub for travel and migration. Molecular analysis can further improve our understanding. Additionally, the global public health community must urgently prioritise the development of novel therapeutic agents for the treatment of gonorrhoea. Full article

(This article belongs to the Special Issue Therapy of Infectious Diseases Among Children and Adults: The Role of Antibiotics in Daily Practice)

15 pages, 6378 KiB

Open AccessArticle

Development of an Effective and Cost-Saving Synergistic-Antibacterial Therapy for Prevention of Endophthalmitis

by Huy Dong, Phat Tran, Keaton Luth, Dana Thalman, Coby Ray, Pamela Lin, Staci Moss, Abdul Hamood, David McCartney and Ted W. Reid

Antibiotics 2025, 14(6), 588; https://doi.org/10.3390/antibiotics14060588 (registering DOI) - 7 Jun 2025

Abstract

Background: Endophthalmitis, associated with intraocular procedures, is an infection of the eye that can rapidly result in substantial irreversible loss of vision and may even lead to removal of the eye. Prevention strategies vary globally and often include antibiotic use—often consisting of a [...] Read more.

Background: Endophthalmitis, associated with intraocular procedures, is an infection of the eye that can rapidly result in substantial irreversible loss of vision and may even lead to removal of the eye. Prevention strategies vary globally and often include antibiotic use—often consisting of a broad-spectrum mono-therapeutic agent. The purpose of this study is to test the efficacy and value of combinations of cefuroxime (cefu), cefazolin (cefa), azithromycin (azith), and/or tobramycin (tob) as alternatives to the use of moxifloxacin. We looked for synergism since these antimicrobials used different mechanisms of inhibition. Methods: Initially, we examined individual antimicrobials to determine the minimal bactericidal concentrations (MBC) of each individual treatment against Klebsiella pneumonia, Pseudomonas aeruginosa, Staphylococcus aureus, two clinical isolates of MRSA, and Staphylococcus epidermidis, by both the Zone of Inhibition (ZOI) and the Colony Forming Unit (CFU) assays. We then used these data in a combinatorial study. Results: We found combinations that were synergistic against all the bacteria tested, resulting in total eradication [8 logs] of all bacteria. We found that the ZOI assay provided less consistent results than the CFU assays. Conclusions: We have found combinations of these antimicrobials that were synergistic in the total eradication (8 logs) of all bacteria tested. These three combinations were: cefuroxime/azithromycin; azithromycin/tobramycin; and cefuroxime/tobramycin. Moxifloxacin (Vigamox) did not completely eradicate Staphylococcus epidermidis. These combinations can then be used as eye drops to serve as a prophylactic for endophthalmitis after eye injections and eye surgery. Full article

(This article belongs to the Section The Global Need for Effective Antibiotics)

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14 pages, 1086 KiB

Open AccessReview

Challenges of Carbapenem-Resistant Enterobacteriaceae in the Development of New β-Lactamase Inhibitors and Antibiotics

by Pierre Leroux, Charleric Bornet, Jean-Michel Bolla and Anita Cohen

Antibiotics 2025, 14(6), 587; https://doi.org/10.3390/antibiotics14060587 (registering DOI) - 7 Jun 2025

Abstract

Nowadays, antimicrobial resistance (AMR) is a growing global health threat, with carbapenem-resistant Enterobacteriaceae (CRE) posing particular concern due to limited treatment options. In fact, CRE have been classified as a critical priority by the World Health Organization (WHO). Carbapenem resistance results from complex [...] Read more.

Nowadays, antimicrobial resistance (AMR) is a growing global health threat, with carbapenem-resistant Enterobacteriaceae (CRE) posing particular concern due to limited treatment options. In fact, CRE have been classified as a critical priority by the World Health Organization (WHO). Carbapenem resistance results from complex mechanisms, often combining the production of hydrolytic enzymes such as β-lactamases with reduced membrane permeability and efflux system induction. The Ambler classification is an effective tool for differentiating the characteristics of serine-β-lactamases (SβLs) and metallo-β-lactamases (MβLs), including ESβLs (different from carbapenemases), KPC, NDM, VIM, IMP, AmpC (different from carbapenemases), and OXA-48. Recently approved inhibitor drugs, such as diazabicyclooctanones and boronic acid derivatives, only partially address this problem, not least because of their ineffectiveness against MβLs. However, compared with taniborbactam, xeruborbactam is the first bicyclic boronate in clinical development with a pan-β-lactamase inhibition spectrum, including the IMP subfamily. Recent studies explore strategies such as chemical optimization of β-lactamase inhibitor scaffolds, novel β-lactam/β-lactamase inhibitor combinations, and siderophore–antibiotic conjugates to enhance bacterial uptake. A deeper understanding of the mechanistic properties of the active sites enables rational drug design principles to be established for inhibitors targeting both SβLs and MβLs. This review aims to provide a comprehensive overview of current therapeutic strategies and future perspectives for the development of carbapenemase inhibitor drug candidates. Full article

(This article belongs to the Special Issue Discovery and Synthesis of Antimicrobial Compounds Against Multidrug Resistance)

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12 pages, 861 KiB

Open AccessArticle

Impact of Cooking Procedures on Coccidiostats in Poultry Muscle

by Rui R. Martins, André M. P. T. Pereira, Liliana J. G. Silva, Sofia C. Duarte, Andreia Freitas and Angelina Pena

Antibiotics 2025, 14(6), 586; https://doi.org/10.3390/antibiotics14060586 (registering DOI) - 7 Jun 2025

Abstract

Background/Objectives: Poultry meat is a popular and nutritious food, valued for its high protein content and healthy fat profile. However, like other animal products, it can contain pharmaceutical residues, including coccidiostats, antimicrobials commonly used to prevent parasitic infections caused by Eimeria species. While [...] Read more.

Background/Objectives: Poultry meat is a popular and nutritious food, valued for its high protein content and healthy fat profile. However, like other animal products, it can contain pharmaceutical residues, including coccidiostats, antimicrobials commonly used to prevent parasitic infections caused by Eimeria species. While most monitoring focuses on raw meat, it is important to understand how these compounds behave during cooking to assess potential health risks better and ensure food safety. Methods: This study examined how five different cooking methods (roasting, grilling, and microwaving, beer and wine marinating) affect the levels of eight coccidiostat residues in 45 samples of poultry muscle collected from a supermarket located in the center of mainland Portugal from May to July 2024. After applying different cooking procedures, ionophore and synthetic coccidiostat residue levels were measured using solid–liquid extraction followed by ultrahigh-performance liquid chromatography with tandem mass spectrometry (UHPLC-MS/MS). Results are expressed as percentages of the original concentrations: 100% indicates stability, values above 100% suggest a relative increase (often due to moisture loss), and values below 100% reflect a decrease, likely from heat degradation. Results: Roasting, grilling, and microwaving all increased residue concentrations—up to 198.5%, 180.1%, and 158.4%, respectively. In contrast, marinating meat in wine or beer before cooking reduced residues to 73.1% and 72.0%, suggesting a mitigating effect. The initial concentration also influenced the outcome: samples fortified at the maximum residue limit (MRL) had an overall higher mean concentration after cooking (148.3%,) than those fortified at twice the MRL (2 MRL), which averaged 124.5%. Conclusions: These results show that cooking can significantly alter coccidiostat residue levels depending on the cooking procedures and initial concentration. Ongoing monitoring and further research are essential to better understand how cooking affects these residues and their by-products. This knowledge is key to improving food safety practices and refining consumer health risk assessments. Full article

(This article belongs to the Special Issue Research Advances in Antimicrobial Stewardship, Residues and Resistance in Veterinary and Environmental Science)

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8 pages, 213 KiB

Open AccessArticle

Periprosthetic Joint Infection in Unicompartmental vs. Total Knee Arthroplasty: Microbiological Spectrum and Management Outcomes

by Ali Said Nazlıgül, Şahan Güven, Yasin Erdoğan, Ahmet Fırat, Metin Doğan and Mustafa Akkaya

Antibiotics 2025, 14(6), 585; https://doi.org/10.3390/antibiotics14060585 - 6 Jun 2025

Abstract

Background/Objectives: Periprosthetic joint infection (PJI) is a severe complication following both total knee arthroplasty (TKA) and unicompartmental knee arthroplasty (UKA). While the microbiological profile of TKA PJI has been well characterized, limited data exist regarding UKA PJIs. This study aimed to compare [...] Read more.

Background/Objectives: Periprosthetic joint infection (PJI) is a severe complication following both total knee arthroplasty (TKA) and unicompartmental knee arthroplasty (UKA). While the microbiological profile of TKA PJI has been well characterized, limited data exist regarding UKA PJIs. This study aimed to compare the causative microorganisms and surgical treatment outcomes in PJI cases following UKA and TKA. Methods: This retrospective cohort study included 82 patients (71 TKA and 11 UKA) who underwent surgical treatment for PJI between January 2017 and May 2024. PJI was diagnosed based on the Musculoskeletal Infection Society (MSIS) criteria. Treatment strategies included debridement, antibiotics, and implant retention (DAIR) or two-stage revision arthroplasty. Microbiological data were extracted from intraoperative cultures. Fisher’s exact test and the Mann–Whitney U test were used for statistical comparisons. Results: Gram-positive organisms, primarily Staphylococcus aureus and coagulase-negative staphylococci, were isolated in all UKA PJIs. In contrast, the TKA group demonstrated greater microbial diversity, including Gram-negative bacilli, polymicrobial infections, and a higher rate of culture-negative cases (33.8% vs. 18.2%). DAIR was performed more frequently in UKA cases (72.7% vs. 28.2%, p = 0.002). Recurrence rates following DAIR were similar in both groups (12.5% in UKA, 20.0% in TKA, p = 1.000). Two-stage revision resulted in no recurrence in UKA and a 9.8% recurrence rate in TKA patients. Conclusions: UKA PJIs appear to be microbiologically less complex than TKA PJI cases, with Gram-positive organisms predominating. Despite these differences, the outcomes of surgical treatment—both DAIR and two-stage revision—were comparable between groups. Standard PJI treatment principles may be applicable to both arthroplasty types; however, larger prospective studies are needed to confirm these findings. Full article

(This article belongs to the Special Issue Periprosthetic Joint Infection: Understanding the Epidemiology, Pathogenesis, Diagnosis and Treatment Options)

14 pages, 1347 KiB

Open AccessArticle

Genomic Characterization of Carbapenem-Resistant Acinetobacter baumannii (OXA-23) and Klebsiella pneumoniae (KPC-2) Causing Hospital-Acquired Infections in Dogs

by Isabela Pádua Zanon, João Victor Ferreira Campos, Yasmin Gonçalves de Castro, Isadora Maria Soares de Melo, Flávia Figueira Aburjaile, Bertram Brenig, Vasco Azevedo and Rodrigo Otávio Silveira Silva

Antibiotics 2025, 14(6), 584; https://doi.org/10.3390/antibiotics14060584 - 6 Jun 2025

Abstract

Background/Objectives: Antimicrobial resistance is a major global health threat. Among the most problematic pathogens are carbapenem-resistant Acinetobacter baumannii and Klebsiella pneumoniae, which are significant causes of mortality in humans, particularly in the context of nosocomial infections. In companion animals, these bacteria have [...] Read more.

Background/Objectives: Antimicrobial resistance is a major global health threat. Among the most problematic pathogens are carbapenem-resistant Acinetobacter baumannii and Klebsiella pneumoniae, which are significant causes of mortality in humans, particularly in the context of nosocomial infections. In companion animals, these bacteria have been reported mainly as colonizers of healthy animals or, less frequently, in community-acquired infections. However, no confirmed cases of healthcare-associated infections caused by these species have been documented in this population. This study reports the first confirmed fatal cases of infection with carbapenem-resistant A. baumannii and KPC-producing K. pneumoniae in dogs. Methods: Three hospitalized dogs developed infections associated with distinct anatomical devices, including a venous catheter, an endotracheal tube, and a Penrose drain. Bacterial isolation followed by antimicrobial susceptibility testing identified carbapenem-resistant A. baumannii and K. pneumoniae. The isolates were subsequently subjected to additional antimicrobial resistance tests and whole-genome sequencing (WGS). Results: WGS confirmed the presence of the OXA-23 carbapenemase gene in both A. baumannii isolates and the KPC-2 carbapenemase gene was detected in the K. pneumoniae strain. All three strains exhibited resistance to multiple antimicrobial classes, including β-lactams (amoxicillin-clavulanic acid, ampicillin, cephalotin, piperacillin-tazobactam, cefoxitin, ceftiofur, cefotaxime, ertapenem, imipenem and meropenem), aminoglycosides (gentamicin, neomycin), tetracyclines (doxycycline, tetracycline and oxytetracycline), fluoroquinolones (ciprofloxacin, enrofloxacin), and folate pathway antagonists (trimethoprim-sulfamethoxazole). Multilocus sequence typing identified two high-risk clones: K. pneumoniae ST340 (CC258) and A. baumannii ST15 (CC15). Single nucleotide polymorphism analysis confirmed a high degree of genetic similarity between these isolates and strains previously associated with human infections in Brazil. Conclusions: These findings provide the first evidence of fatal, healthcare-associated infections caused by these multidrug-resistant pathogens in dogs and underscore the need to strengthen surveillance and infection control practices in veterinary hospitals. Furthermore, the results raise concerns about the potential of companion animals to act as reservoirs for multidrug-resistant organisms of public health relevance. Full article

(This article belongs to the Special Issue Antimicrobial Resistance: Epidemiology and Implications for Veterinary Medicine)

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17 pages, 623 KiB

Open AccessArticle

Landscape of Post-Marketing Requirements Under the Pediatric Research Equity Act for Antibiotics from 2009–2024

by Daniel Selig, Funmi Aminu, Sue Cammarata, Ting Chen, Lauren Dolak, Stephen Duprez, Stephanie Ecker, Lisa Gault, Sandra George, Margaret Harkins, Clayton Litchmore, Michael Serenko, William Waverczak and Doug Girgenti

Antibiotics 2025, 14(6), 583; https://doi.org/10.3390/antibiotics14060583 - 6 Jun 2025

Abstract

Background/Objectives: We reviewed Post-Marketing Requirements (PMRs) under the Pediatric Research Equity Act (PREA) for antibiotics approved in adults from 2009 to 2024 to better understand factors associated with PMR study completion. Methods: Initial PMRs, including study design and completion timelines were extracted [...] Read more.

Background/Objectives: We reviewed Post-Marketing Requirements (PMRs) under the Pediatric Research Equity Act (PREA) for antibiotics approved in adults from 2009 to 2024 to better understand factors associated with PMR study completion. Methods: Initial PMRs, including study design and completion timelines were extracted from Food and Drug Administration (FDA) approval letters. Studies were cross-referenced at clinicaltrials.gov, with follow-up from adult approval to study completion or through 31 December 2024. Results: Eighteen antibiotics were approved in adults from 2009 to 2024, with 53 associated PREA PMRs. A total of nine PMRs were excluded from analysis (six exclusions for projected study completion dates on or after 12/31/2024, one exclusion due to lack of information, and two exclusions because the study type was not categorizable as Phase 1 or Phase 2). Of the 44 remaining PMRs in the analysis set, the median pediatric study follow-up time from adult approval was 5.3 years (range 0.94 to 11.5 years), with a study completion rate of 54.5% (N = 24). Small- and medium-sized companies had a study completion rate of 10% (N = 2/20) over a median of 6.44 years of follow-up, with no pediatric approvals. Large pharmaceutical corporations had a significantly higher study completion rate of 91.6% (N = 22/24; adjusted hazard ratio 20.3 95%CI, 5.02 to 82.4) over a median follow-up time of 4.7 years and achieved pediatric approval with labelling updates for 75% of antibiotics (N = 6/8). Conclusions: Compared to larger organizations, smaller pharmaceutical companies have experienced difficulty in PREA PMR antibiotic study completion, which may be related to financial difficulties in the challenging market for antibiotics. To improve PMR study completion, smaller companies require continued financial support and innovation in study design. For pediatric antibiotic development, the FDA accepts the extrapolation of efficacy from well-conducted randomized adult trials (i.e., pharmacokinetics (PK) and the safety approach). Therefore, sponsors should consider the use of single-arm, non-comparative PK and safety study designs to reduce the size and scope of trials. Sponsors should also assess whether the evaluation of an antibiotic is necessary in adolescents, or if data in a surrogate population of adults (e.g., low-weight adults) may serve as adequate evidence for adolescent approval. Full article

(This article belongs to the Special Issue New Drugs, Innovative Antimicrobial Approaches, and Optimized Dosages: Bridging Research and Clinical Practice)

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23 pages, 506 KiB

Open AccessArticle

Design and Synthesis of Hybrid Compounds for Potential Treatment of Bacterial Co-Infections: In Vitro Antibacterial and In Silico Studies

by Vuyolwethu Khwaza, Opeoluwa O. Oyedeji, Eric Morifi, Mutshinyalo Nwamadi, Thierry Youmbi Fonkui, Derek Tantoh Ndinteh and Blessing A. Aderibigbe

Antibiotics 2025, 14(6), 582; https://doi.org/10.3390/antibiotics14060582 - 6 Jun 2025

Abstract

Background: The need for innovative therapeutic strategies to enhance patient outcomes has increased due to the rise in bacterial co-infections associated with COVID-19. Methods: In this study, ten hybrid compounds were synthesized by combining two known pharmaceutical scaffolds to enhance antibacterial activity and [...] Read more.

Background: The need for innovative therapeutic strategies to enhance patient outcomes has increased due to the rise in bacterial co-infections associated with COVID-19. Methods: In this study, ten hybrid compounds were synthesized by combining two known pharmaceutical scaffolds to enhance antibacterial activity and overcome resistance mechanisms. The synthesized compounds were evaluated for their antibacterial activity against five Gram-negative and seven Gram-positive bacterial strains. In silico pharmacokinetic and drug-likeness properties of selected active compounds (12–16, 19, 21, and 23) were predicted using the SwissADME web tool. Results: Compounds 12–16, 19, 21, and 23 demonstrated significant antibacterial activity, with compound 16 (a ciprofloxacin-containing hybrid) exhibiting the most potent effect, showing a minimum inhibitory concentration (MIC) of 7.8125 µg/mL against all tested bacterial strains. The in silico analysis revealed favorable pharmacokinetic profiles, drug-likeness, lipophilicity, and water solubility of most hybrid compounds. Discussion: The synthesized hybrid compounds exhibited enhanced antibacterial activity and desirable pharmacokinetic properties, particularly compound 16. These findings suggest the potential of these molecules in combating bacterial pathogens, especially those implicated in co-infections in COVID-19 infections. Conclusions: The study presents promising hybrid antibacterial agents with potential application as adjunct therapies for treating COVID-19-associated bacterial co-infections. Further investigation is needed, which may lead to effective treatments for managing secondary bacterial infections in viral disease contexts. Full article

(This article belongs to the Special Issue Strategies for the Design of Hybrid-Based Antimicrobial Compounds)

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15 pages, 264 KiB

Open AccessReview

Current Applications and the Future of Phage Therapy for Periprosthetic Joint Infections

by Arian Ocean Abedi, Armita Armina Abedi, Tristan Ferry and Mustafa Citak

Antibiotics 2025, 14(6), 581; https://doi.org/10.3390/antibiotics14060581 - 6 Jun 2025

Abstract

Periprosthetic joint infections (PJI) present significant challenges in orthopedic surgery, largely due to the complexity of treating antibiotic-resistant infections. Phage therapy, which utilizes bacteriophages to target bacterial pathogens, offers a promising supplement to traditional antimicrobial methods. This review discusses the current applications of [...] Read more.

Periprosthetic joint infections (PJI) present significant challenges in orthopedic surgery, largely due to the complexity of treating antibiotic-resistant infections. Phage therapy, which utilizes bacteriophages to target bacterial pathogens, offers a promising supplement to traditional antimicrobial methods. This review discusses the current applications of phage therapy in the management of PJI, exploring its underlying mechanisms, clinical outcomes, and practical considerations. We also explore advances in phage therapy technology, including the development of phage cocktails, bioengineered phages, and combination therapies with antibiotics, which enhance the specificity and effectiveness of treatments. Furthermore, we address the future potential of phage therapy to be integrated into standard treatment protocols, focusing on ongoing innovations and research areas.The regulatory and ethical aspects of phage therapy in clinical settings are also discussed. By offering a comprehensive evaluation of both the current state and prospects of phage therapy, this review aims to inform clinical practice and stimulate further research into this innovative treatment modality for PJI management. Full article

(This article belongs to the Special Issue Bacteriophage Therapy a Renaissance Weapon Recent Developments and Application, 2nd Edition)

10 pages, 350 KiB

Open AccessArticle

Distribution and Clinical Impact of Helicobacter pylori Virulence Factors in Epstein–Barr-Virus-Associated Gastric Cancer

by Jin Hee Noh, Ji Yong Ahn, Hee Kyong Na, Jeong Hoon Lee, Kee Wook Jung, Do Hoon Kim, Kee Don Choi, Ho June Song, Gin Hyug Lee and Hwoon-Yong Jung

Antibiotics 2025, 14(6), 580; https://doi.org/10.3390/antibiotics14060580 - 5 Jun 2025

Abstract

Background: Helicobacter pylori (HP) and Epstein–Barr virus (EBV) coinfection lead to chronic inflammation and contribute to the development of gastric cancer. However, studies examining the association between HP virulence factors and EBV infection in gastric cancer are limited. This study investigated the [...] Read more.

Background: Helicobacter pylori (HP) and Epstein–Barr virus (EBV) coinfection lead to chronic inflammation and contribute to the development of gastric cancer. However, studies examining the association between HP virulence factors and EBV infection in gastric cancer are limited. This study investigated the polymorphisms of HP virulence factors associated with EBV infection and their effects on clinical outcomes in EBV-associated gastric cancer (EBVaGC). Methods: A total of 96 HP isolates from 54 patients with gastric cancer were divided and analyzed based on EBV coinfection status. Polymerase chain reaction amplifications of virulence factors were conducted using DNA extracts from HP isolates cultured from gastric mucosal specimens. Results: EBV infection was significantly associated with gastric carcinoma with lymphoid stroma morphology and a proximal location in the stomach. Most HP strains from patients with gastric cancer were positive for cagA (100.0%), vacA (100.0%), and iceA1 (87.5%). Among HP isolates with EBV coinfection, the prevalence of iceA2 (21.7% vs. 0.0%, p < 0.001) and ureA (21.7% vs. 4.0%, p = 0.009) was significantly more frequent, and that of iceA1 (78.3% vs. 96.0%, p = 0.009) and vacA s1a (4.3% vs. 22.0%, p = 0.012) was less frequent than those of EBV– colonies. Multivariate analysis indicated that ureA (odds ratio, 6.148; 95% confidence interval [CI], 1.221 to 30.958; p = 0.028) was associated with EBVaGC. No significant difference in clinical outcomes was observed based on the presence of ureA expression in EBVaGC. Conclusions: In gastric cancer, regardless of EBV infection, most HP strains were highly virulent, testing positive for cagA, vacA, and iceA1. Although ureA was significantly associated with EBV infection, it did not influence the clinical outcomes of EBVaGC. Full article

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11 pages, 947 KiB

Open AccessArticle

Candidozyma auris Outbreak and Its Effective Control in a General Hospital

by Flora V. Kontopidou, Maria Antonopoulou, Anastasia Votsi, Vassiliki Papoutsaki, Vassiliki Bereri, Evangelia Kourkoulou, Amalia Rompola, Georgia Tsokou, Anna Pavli, Olga Maria Koutantelia, Maria Siopi, Sevasti Leventaki, Joseph Meletiadis and George L. Daikos

Antibiotics 2025, 14(6), 579; https://doi.org/10.3390/antibiotics14060579 - 5 Jun 2025

Abstract

Background/Objectives: Candidozyma auris (C. auris) is a multidrug-resistant pathogen recognized as a serious global public health threat. Herein, we report a C. auris outbreak that was successfully contained in a general hospital located in Athens, Greece. Methods: This study was [...] Read more.

Background/Objectives: Candidozyma auris (C. auris) is a multidrug-resistant pathogen recognized as a serious global public health threat. Herein, we report a C. auris outbreak that was successfully contained in a general hospital located in Athens, Greece. Methods: This study was conducted between December 2021 and December 2023. Upon identification of the first imported case of C. auris, the following infection control measures were applied in a stepwise approach: the promotion of hand hygiene, contact precautions and isolation, chlorhexidine gluconate bathing of patients, enhanced environmental cleaning, and active surveillance cultures of all high-risk patients upon admission. Active surveillance cultures were performed weekly in non-colonized ICU patients. Results: A total of 1564 screening samples from 890 patients were analyzed. Sixty-three patients were identified to be colonized and three to be infected with C. auris. After implementing screening and enhanced environmental cleaning, the quarterly incidence of hospital-acquired cases decreased from 0.37 to 0.04 cases per 1000 patient-days (slope of linear trend: −0.08; 95% CI: −0.16 to −0.0004; p = 0.05), despite the continuous inflow of already colonized patients. Conclusions: A bundle of infection control measures, including active surveillance cultures upon admission and enhanced environmental cleaning, can contain C. auris dissemination in acute healthcare settings. Full article

(This article belongs to the Special Issue A Themed Issue in Honor of Professor Helen Giamarellou—Outstanding Contributions in the Fields of Antimicrobial Resistance and Difficult-to-Treat Resistance Pathogens)

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19 pages, 1281 KiB

Open AccessArticle

Phenotypic and Genotypic Characterization of ESBL and AmpC β-Lactamase-Producing E. coli Isolates from Poultry in Northwestern Romania

by Anca Rus, Iulia-Maria Bucur, Kalman Imre, Andreea Talida Tirziu, Andrei Alexandru Ivan, Radu Valentin Gros, Alex Cristian Moza, Sebastian Alexandru Popa, Alexandra Ban-Cucerzan and Emil Tirziu

Antibiotics 2025, 14(6), 578; https://doi.org/10.3390/antibiotics14060578 - 5 Jun 2025

Abstract

Background/Objectives: The widespread use of antibiotics in animal husbandry has led to an increase in antimicrobial-resistant Escherichia coli, particularly strains producing extended-spectrum β-lactamases (ESBL) and AmpC β-lactamases. This study aimed to isolate and characterize such strains from fecal samples of broiler [...] Read more.

Background/Objectives: The widespread use of antibiotics in animal husbandry has led to an increase in antimicrobial-resistant Escherichia coli, particularly strains producing extended-spectrum β-lactamases (ESBL) and AmpC β-lactamases. This study aimed to isolate and characterize such strains from fecal samples of broiler chickens (n = 71) and slaughtered turkeys (n = 31) in northwestern Romania. Methods: Antimicrobial susceptibility testing and PCR were used to evaluate phenotypic resistance patterns and detect the presence of resistance genes (AmpC, blaZ, and blaTEM). Results: The results showed that 55% of turkey and 61% of broiler isolates were presumptive ESBL/AmpC producers. Among all isolates, 50% were classified as extensively drug-resistant (XDR), 44% as multidrug-resistant (MDR), and only 6% were fully susceptible. Gene detection revealed an overall prevalence of 44.2% for AmpC, 72.7% for blaZ, and 58.1% for blaTEM, yielding a total penetrance of 51.09%. The diagnostic odds ratio (DOR) values, ranging from 0.67 to 81, suggest the efficacy of the antibiotic susceptibility testing method used in detecting the presence of these resistance genes. Conclusion: Overall, these findings highlight a significant burden of antimicrobial-resistant, poultry-associated E. coli strains, warranting stricter antimicrobial stewardship. Full article

(This article belongs to the Special Issue Veterinary Microbiology and Antimicrobial Resistance—the One Health Approach)

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14 pages, 488 KiB

Open AccessArticle

Use of Probiotics During Antibiotic Therapy in Pediatrics: A Cross-Sectional Survey of Italian Primary Care Pediatricians

by Giacomo Biasucci, Maria Elena Capra, Antonella Giudice, Delia Monopoli, Brigida Stanyevic, Roberta Rotondo, Alessandro Mucci, Cosimo Neglia, Beatrice Campana and Susanna Esposito

Antibiotics 2025, 14(6), 577; https://doi.org/10.3390/antibiotics14060577 - 4 Jun 2025

Abstract

Background: Antibiotic-associated diarrhea (AAD) is a common adverse effect of pediatric antibiotic therapy, often linked to gut microbiota disruption. Probiotics may help prevent AAD when appropriately selected and dosed. Methods: We conducted a cross-sectional survey to assess the attitudes and prescribing habits [...] Read more.

Background: Antibiotic-associated diarrhea (AAD) is a common adverse effect of pediatric antibiotic therapy, often linked to gut microbiota disruption. Probiotics may help prevent AAD when appropriately selected and dosed. Methods: We conducted a cross-sectional survey to assess the attitudes and prescribing habits of Italian Primary Care Pediatricians (PCPs) regarding the use of probiotics during antibiotic treatment. A digital questionnaire comprising 23 mandatory multiple-choice items was distributed to 980 PCPs across Italy between July and October 2024. The survey explored probiotic prescribing frequency, indications, strains used, dosage, duration, and sources of information. Descriptive statistics and subgroup analyses by years of clinical experience were performed. Results: A total of 279 PCPs (response rate: 28%) completed the survey; 66.7% were female, and 77.1% had over 20 years of clinical experience. Probiotics were prescribed primarily to restore microbiota balance (81.1%) and prevent AAD (47.3%). The most common barriers included additional cost (35.1%) and perceived lack of evidence (26.5%). Lactobacillus rhamnosus GG (91.8%) and Saccharomyces boulardii (41.9%) were the most frequently recommended strains. Daily doses of 5–10 billion CFU were preferred by 44.4% of respondents, with typical durations of 1–2 weeks (40.1%) or one week (31.2%). Conclusions: Probiotics are widely used by Italian PCPs during antibiotic therapy, especially for microbiota support and AAD prevention. However, variability in practice underscores the need for clearer, evidence-based guidelines regarding probiotic strain selection, dosing, and treatment duration. Full article

(This article belongs to the Section Antibiotics Use and Antimicrobial Stewardship)

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17 pages, 2295 KiB

Open AccessArticle

The Prevalence of Antimicrobial Resistance Genes in the Environments of Small Ruminant Farms from Central Portugal

by Jaqueline T. Bento, Sara Gomes-Gonçalves, Rita Cruz, Fernando Esteves, Alexandra Lameira Baptista, Maria Aires Pereira, Pedro Caseiro, Pedro Carreira, Luís Figueira, João R. Mesquita, Adriano A. Bordalo and Ana Machado

Antibiotics 2025, 14(6), 576; https://doi.org/10.3390/antibiotics14060576 - 4 Jun 2025

Abstract

Background: Antimicrobial resistance is a pressing global concern affecting both human and animal health, with environment playing a key role in the dissemination of resistance determinants. This study aimed to investigate the presence of antimicrobial resistance genes (ARGs) associated with tetracyclines, β-lactams, macrolides, [...] Read more.

Background: Antimicrobial resistance is a pressing global concern affecting both human and animal health, with environment playing a key role in the dissemination of resistance determinants. This study aimed to investigate the presence of antimicrobial resistance genes (ARGs) associated with tetracyclines, β-lactams, macrolides, and sulfonamides in environmental matrices collected from 65 sheep and goat farms in central Portugal. Methods: Environmental samples, including water, soil, pasture, and bedding, were analyzed through qPCR for the detection of clinically relevant ARGs. Results: ARGs were detected in 83% of the samples, with over half exhibiting genes from three or more antibiotic classes, suggesting potential multidrug resistance. β-lactamase genes were the most prevalent, followed by those conferring resistance to tetracycline and sulfonamide resistance, while macrolide resistance genes were least frequent. The distribution of ARGs varied by farm type, host species, and municipality. Conclusions: These findings suggest that small ruminant farms serve as important reservoirs for ARGs. The results underscore the need for systematic surveillance and further research into the ecological and genetic factors driving ARG persistence and dissemination in extensive livestock systems, including proper waste management strategies to limit the spread and persistence of antibiotic resistance and mitigate broader public health risks. Full article

(This article belongs to the Special Issue Genetic Characterization of Antimicrobial Resistance under the One Health Approach)

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20 pages, 4470 KiB

Open AccessArticle

Cellulose Nanocrystal/Zinc Oxide Bio-Nanocomposite Activity on Planktonic and Biofilm Producing Pan Drug-Resistant Clostridium perfringens Isolated from Chickens and Turkeys

by Ismail Amin, Adel Abdelkhalek, Azza S. El-Demerdash, Ioan Pet, Mirela Ahmadi and Norhan K. Abd El-Aziz

Antibiotics 2025, 14(6), 575; https://doi.org/10.3390/antibiotics14060575 - 3 Jun 2025

Abstract

Background/Objectives: Clostridium perfringens is a normal inhabitant of the intestinal tract of poultry, and it has the potential to induce cholangiohepatitis and necrotic enteritis (NE). The poultry industry suffers significant financial losses because of NE, and treatment becomes more challenging due to [...] Read more.

Background/Objectives: Clostridium perfringens is a normal inhabitant of the intestinal tract of poultry, and it has the potential to induce cholangiohepatitis and necrotic enteritis (NE). The poultry industry suffers significant financial losses because of NE, and treatment becomes more challenging due to resistant C. perfringens strains. Methods: The antimicrobial and antibiofilm activities of cellulose nanocrystals/zinc oxide nanocomposite (CNCs/ZnO) were assesses against pan drug-resistant (PDR) C. perfringens isolated from chickens and turkeys using phenotypic and molecular assays. Results: The overall prevalence rate of C. perfringens was 44.8% (43.75% in chickens and 58.33% in turkeys). Interestingly, the antimicrobial susceptibility testing of C. perfringens isolates revealed the alarming PDR (29.9%), extensively drug-resistant (XDR, 54.5%), and multidrug-resistant (MDR, 15.6%) isolates, with multiple antimicrobial resistance (MAR) indices ranging from 0.84 to 1. All PDR C. perfringens isolates could synthesize biofilms; among them, 21.7% were strong biofilm producers. The antimicrobial potentials of CNCs/ZnO against PDR C. perfringens isolates were evaluated by the agar well diffusion and broth microdilution techniques, and the results showed strong antimicrobial activity of the green nanocomposite with inhibition zones’ diameters of 20–40 mm and MIC value of 0.125 µg/mL. Moreover, the nanocomposite exhibited a great antibiofilm effect against the pre-existent biofilms of PDR C. perfringens isolates in a dose-dependent manner [MBIC50 up to 83.43 ± 1.98 for the CNCs/ZnO MBC concentration (0.25 μg/mL)]. The transcript levels of agrB quorum sensing gene and pilA2 type IV pili gene responsible for biofilm formation were determined by the quantitative real time-PCR technique, pre- and post-treatment with the CNCs/ZnO nanocomposite. The expression of both genes downregulated (0.099 ± 0.012–0.454 ± 0.031 and 0.104 ± 0.006–0.403 ± 0.035, respectively) when compared to the non-treated isolates. Conclusions: To the best of our knowledge, this is the first report of CNCs/ZnO nanocomposite’s antimicrobial and antibiofilm activities against PDR C. perfringens isolated from chickens and turkeys. Full article

(This article belongs to the Special Issue Antimicrobial and Antibiofilm Activity by Natural Compounds)

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