Virulence, Antimicrobial Resistance and Biofilm Production in Veterinary, Zoonotic and Food-Related Pathogens

A special issue of Antibiotics (ISSN 2079-6382). This special issue belongs to the section "Antibiotics in Animal Health".

Deadline for manuscript submissions: 28 February 2026 | Viewed by 3846

Special Issue Editors


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Guest Editor
Department of Animal Health, Universidad de León, León, Spain
Interests: antimicrobial resistance; biofilm; genomics; microbiology; microbiome; veterinary pathogens; zoonosis

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Guest Editor
Department of Food Hygiene and Technology, Universidad de León, León, Spain
Interests: biofilm; fermented beverages; food-related pathogens; microbial dynamics; microbiome

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Guest Editor
Department of Animal Health, Universidad de León, León, Spain
Interests: antimicrobial resistance; biofilm; microbiology; porcine respiratory disease complex; vaccination
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Special Issue Information

Dear Colleagues,

The emergence and persistence of virulent, antimicrobial-resistant pathogens in veterinary and food-related environments pose significant threats to both animal and human health. This Special Issue aims to explore the complex interplay between virulence factors, antimicrobial resistance mechanisms, and biofilm production in veterinary, zoonotic, and food-related pathogens.

Understanding these interactions is critical for developing effective strategies to control infections, ensure food safety, and mitigate the spread of resistance. Contributions to this issue will encompass a range of topics, including the molecular mechanisms underlying virulence and resistance, the impact of biofilm formation on pathogen survival and treatment efficacy, and innovative approaches for detection and intervention.

By bringing together cutting-edge research from leading experts, this Special Issue seeks to provide a comprehensive overview of current challenges and advancements in the field. We aim to foster interdisciplinary collaboration and inspire new insights that can lead to improved therapeutic and preventative measures.

Through a deeper understanding of these critical aspects of pathogen biology, we hope to contribute to the development of more effective policies and practices that safeguard animal health, food security, and public health.

Dr. Óscar Mencía-Ares
Dr. Paula Fernández-Gómez
Dr. Sonia Martinez
Guest Editors

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Keywords

  • animal health
  • antimicrobial resistance
  • biofilm
  • food-borne pathogens
  • microbiology
  • pathogenicity
  • public health
  • veterinary pathogens
  • virulence
  • zoonosis

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Published Papers (5 papers)

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Research

12 pages, 319 KiB  
Communication
Raw Sheep Milk as a Reservoir of Multidrug-Resistant Staphylococcus aureus: Evidence from Traditional Farming Systems in Romania
by Răzvan-Dragoș Roșu, Adriana Morar, Alexandra Ban-Cucerzan, Mirela Imre, Sebastian Alexandru Popa, Răzvan-Tudor Pătrînjan, Alexandra Pocinoc and Kálmán Imre
Antibiotics 2025, 14(8), 787; https://doi.org/10.3390/antibiotics14080787 (registering DOI) - 2 Aug 2025
Abstract
Background/Objectives: Staphylococcus aureus is a major pathogen of concern in raw milk due to its potential to cause foodborne illness and its increasing antimicrobial resistance (AMR). In Romania, data on the occurrence and resistance patterns of S. aureus in raw sheep milk [...] Read more.
Background/Objectives: Staphylococcus aureus is a major pathogen of concern in raw milk due to its potential to cause foodborne illness and its increasing antimicrobial resistance (AMR). In Romania, data on the occurrence and resistance patterns of S. aureus in raw sheep milk from traditional farming systems remain limited. This study investigated the presence and antimicrobial resistance of S. aureus in 106 raw sheep milk samples collected from traditional farms in the Banat region of western Romania. Methods: Coagulase-positive staphylococci (CPS) were enumerated using ISO 6888-1:2021 protocols. Isolates were identified at the species level using the Vitek 2 system and molecularly confirmed via PCR targeting the 16S rDNA and nuc genes. Methicillin resistance was assessed by detecting the mecA gene. Antimicrobial susceptibility was determined using the Vitek 2 AST-GP79 card. Results: CPS were detected in 69 samples, with S. aureus confirmed in 34.9%. The mecA gene was identified in 13.5% of S. aureus isolates, indicating the presence of methicillin-resistant S. aureus (MRSA). Resistance to at least two antimicrobials was observed in 97.3% of isolates, and 33 strains (89.2%) met the criteria for multidrug resistance (MDR). The most frequent MDR phenotype involved resistance to lincomycin, macrolides, β-lactams, tetracyclines, and aminoglycosides. Conclusions: The high prevalence of S. aureus, including MRSA and MDR strains, in raw sheep milk from traditional farms represents a potential public health risk, particularly in regions where unpasteurized dairy consumption persists. These findings underscore the need for enhanced hygiene practices, prudent antimicrobial use, and AMR monitoring in small-scale dairy systems. Full article
18 pages, 2560 KiB  
Article
In Vitro Insights into the Anti-Biofilm Potential of Salmonella Infantis Phages
by Jan Torres-Boncompte, María Sanz-Zapata, Josep Garcia-Llorens, José M. Soriano, Pablo Catalá-Gregori and Sandra Sevilla-Navarro
Antibiotics 2025, 14(8), 744; https://doi.org/10.3390/antibiotics14080744 - 24 Jul 2025
Viewed by 382
Abstract
Background/Objectives: As bacteriophage-based strategies to control bacterial pathogens continue to gain momentum, phage therapy is increasingly being explored across various fields. In the poultry industry, efforts to minimize the public health impact of Salmonella have spurred growing interest in phage applications, particularly [...] Read more.
Background/Objectives: As bacteriophage-based strategies to control bacterial pathogens continue to gain momentum, phage therapy is increasingly being explored across various fields. In the poultry industry, efforts to minimize the public health impact of Salmonella have spurred growing interest in phage applications, particularly as prophylactic and disinfecting agents. Although the disinfecting potential of bacteriophages has been recognized, in-depth studies examining their efficacy under varying environmental conditions remain limited. This study focused on evaluating the effectiveness of bacteriophages as disinfecting agents against biofilm-forming Salmonella Infantis under different environments. Methods: A comprehensive screening of biofilm-producing strains was conducted using Congo Red Agar and 96-well plate assays. Two strains with distinct biofilm-forming capacities were selected for further analysis under different environmental conditions: aerobic and microaerobic atmospheres at both 25 °C and 37 °C. The resulting biofilms were then treated with four phage preparations: three individual phages and one phage cocktail. Biofilm reduction was assessed by measuring optical density and CFU/well. Additionally, scanning electron microscopy was used to visualize both untreated and phage-treated biofilms. Results: The results demonstrated that all S. Infantis strains were capable of forming biofilms (21/21). All three phage candidates exhibited biofilm-disrupting activity and were able to lyse biofilm-embedded Salmonella cells. Notably, the lytic efficacy of the phages varied depending on environmental conditions, highlighting the importance of thorough phage characterization prior to application. Conclusions: These findings underscore that the effectiveness of bacteriophages as surface disinfectants can be significantly compromised if inappropriate phages are used, especially in the presence of biofilms. Full article
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16 pages, 1873 KiB  
Article
Antimicrobial Susceptibility Profiles of Staphylococcus aureus and Streptococcus spp. Isolates from Clinical Cases of Waterfowl in Hungary Between 2022 and 2023
by Ádám Kerek, Ábel Szabó and Ákos Jerzsele
Antibiotics 2025, 14(5), 496; https://doi.org/10.3390/antibiotics14050496 - 12 May 2025
Viewed by 766
Abstract
Background: Antimicrobial resistance (AMR) is an escalating concern in both human and veterinary medicine, particularly in the poultry sector, where antibiotic usage is substantial. Streptococcus spp. and Staphylococcus aureus are important pathogens in waterfowl, causing systemic infections. However, there is a significant [...] Read more.
Background: Antimicrobial resistance (AMR) is an escalating concern in both human and veterinary medicine, particularly in the poultry sector, where antibiotic usage is substantial. Streptococcus spp. and Staphylococcus aureus are important pathogens in waterfowl, causing systemic infections. However, there is a significant lack of data regarding their antimicrobial susceptibility patterns in waterfowl populations. This study aims to address this gap by determining the minimum inhibitory concentrations (MICs) of isolates from Hungarian waterfowl farms and evaluating resistance patterns in clinical isolates. Methods: A total of eight S. aureus and 19 Streptococcus isolates were collected from ducks and geese between 2022 and 2023. Antimicrobial susceptibility testing was performed for 15 antimicrobials using the broth microdilution method. Potential associations between MIC values were analyzed using Spearman’s rank correlation test. Results: High MIC values were observed for tetracyclines, phenicols, and fluoroquinolones, in the case of Streptococcus, with 89.5% of isolates exhibiting resistance to doxycycline, 63.2% to florfenicol, and in the case of S. aureus, 25.0% to enrofloxacin. In the case of Streptococcus, a strong positive correlation was identified between tylosin and tiamulin (0.88, p < 0.001), as well as between tylosin and lincomycin (0.75, p < 0.001). A moderate correlation was observed between doxycycline and spectinomycin (0.72, p = 0.03), suggesting potential co-selection mechanisms. Conclusions: Our findings emphasize the necessity of continuous AMR surveillance in the waterfowl industry, particularly for multidrug-resistant strains. Understanding cross-resistance patterns is crucial for developing targeted control measures, and future studies should incorporate whole-genome sequencing to elucidate resistance determinants and co-selection mechanisms. This study highlights the potential public health and veterinary risks associated with AMR in waterfowl and reinforces the importance of responsible antibiotic use and the development of alternative therapeutic strategies in veterinary practice. Full article
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17 pages, 3081 KiB  
Article
Antimicrobial Susceptibility Profiles of Erysipelothrix rhusiopathiae and Riemerella anatipestifer Isolates from Clinical Cases of Waterfowl in Hungary Between 2022 and 2023
by Ádám Kerek, Ábel Szabó and Ákos Jerzsele
Antibiotics 2025, 14(5), 478; https://doi.org/10.3390/antibiotics14050478 - 8 May 2025
Viewed by 682
Abstract
Background:Riemerella anatipestifer and Erysipelothrix rhusiopathiae remain clinically significant pathogens in the waterfowl industry, causing substantial economic losses and posing potential zoonotic risks. Antimicrobial resistance (AMR) continues to spread in the poultry sector, making regular surveillance of bacterial isolates essential. Methods: In [...] Read more.
Background:Riemerella anatipestifer and Erysipelothrix rhusiopathiae remain clinically significant pathogens in the waterfowl industry, causing substantial economic losses and posing potential zoonotic risks. Antimicrobial resistance (AMR) continues to spread in the poultry sector, making regular surveillance of bacterial isolates essential. Methods: In this study, eight R. anatipestifer and eighteen E. rhusiopathiae strains were isolated from clinical cases in Hungarian waterfowl between 2022 and 2023. Minimum inhibitory concentration (MIC) values were determined for antibiotics of veterinary and public health significance. Results: For R. anatipestifer, high resistance rates were observed for spectinomycin, lincomycin, and tiamulin, while beta-lactam antibiotics (amoxicillin, ceftriaxone, and imipenem) demonstrated strong efficacy. Among the E. rhusiopathiae isolates, resistance to amoxicillin (89%) and enrofloxacin (61%) was notable, whereas ceftriaxone and doxycycline exhibited moderate antibacterial effects. Conclusions: Our findings underscore the importance of targeted antimicrobial use in the waterfowl industry. Beta-lactam antibiotics remain effective, whereas rising resistance to fluoroquinolones and aminoglycosides raise serious concerns. Routine AMR surveillance and the adoption of alternative strategies are crucial for controlling infections and maintaining flock health. Full article
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15 pages, 2988 KiB  
Article
Insights into the Virulence and Antimicrobial Resistance of Staphylococcus hyicus Isolates from Spanish Swine Farms
by Oscar Mencía-Ares, Eva Ramos-Calvo, Alba González-Fernández, Álvaro Aguarón-Turrientes, Ana Isabel Pastor-Calonge, Rubén Miguélez-Pérez, César B. Gutiérrez-Martín and Sonia Martínez-Martínez
Antibiotics 2024, 13(9), 871; https://doi.org/10.3390/antibiotics13090871 - 11 Sep 2024
Cited by 1 | Viewed by 1563
Abstract
Staphylococcus hyicus is a significant pathogen in swine, primarily causing exudative epidermitis. Addressing S. hyicus infections requires both the characterization of virulence and antimicrobial resistance (AMR) in farm-recovered isolates. This study aimed to characterize the virulence, AMR, and biofilm formation of S. hyicus [...] Read more.
Staphylococcus hyicus is a significant pathogen in swine, primarily causing exudative epidermitis. Addressing S. hyicus infections requires both the characterization of virulence and antimicrobial resistance (AMR) in farm-recovered isolates. This study aimed to characterize the virulence, AMR, and biofilm formation of S. hyicus isolates from Spanish swine farms. A total of 49 isolates were analyzed, originating from animals with cutaneous, reproductive, and systemic clinical signs. Half of the isolates (49.0%) were positive for at least one virulence factor (VF) gene, with SHETA being the most frequent (28.6%). A high frequency of multidrug resistant (MDR) isolates was observed (83.7%), with significant resistance to commonly used antimicrobials, including lincosamides (83.7%), pleuromutilins (81.6%), penicillins (75.5%), and tetracyclines (73.5%). All isolates exhibited robust in vitro biofilm formation capacity (DC = 15.6 ± 7.0). Significant associations were found between VFs, biofilm formation, and AMR patterns, highlighting the link between the resistance to lincosamides and pleuromutilins (p < 0.001; Φ = 0.57) and macrolides (p < 0.001; Φ = 0.48), and the association of AMR with the ExhC and ExhD VF genes. These findings underscore the need for targeted diagnostics to improve management and therapeutic strategies to mitigate the impact of S. hyicus on swine production. Full article
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