Biofilm Production by Critical Antibiotic-Resistant Pathogens from an Equine Wound.
Authors: Afonso Ana C, Sousa Mariana, Pinto Ana Rita, Cotovio Mário, Simões Manuel, Saavedra Maria José
Journal: Animals : an open access journal from MDPI
Summary
# Editorial Summary: Biofilm Production in Equine Wound Pathogens Chronic equine wounds frequently resist conventional treatment because polymicrobial biofilms establish protective communities that antibiotics cannot penetrate effectively, yet clinical investigation of this problem remains limited in equine practice. Researchers isolated four bacterial strains from a 21-day-old non-healing wound in a Lusitano mare treated only with antiseptic—three *Staphylococcus aureus* isolates and one *Pseudomonas aeruginosa*—and evaluated both their antibiotic resistance profiles and biofilm-forming capacity. The *P. aeruginosa* isolate demonstrated concerning resistance to carbapenems and fluoroquinolones without prior antibiotic exposure at the yard, suggesting possible cross-resistance between antiseptic use and antibiotic resistance; all isolates produced substantial biofilms, though gentamicin achieved 59.3–85.7% biofilm removal at ten times the minimum inhibitory concentration, with *P. aeruginosa* showing the greatest susceptibility at the highest dose. These findings underscore the critical importance of early culture-based diagnosis when chronic wounds fail to respond to standard care, as biofilm-producing pathogens require higher antimicrobial concentrations and potentially alternative treatment strategies such as topical high-concentration gentamicin or mechanical debridement rather than systemic therapy alone. The case also highlights biosecurity implications, as antibiotic-resistant wound pathogens pose transmission risks to other horses, handlers, and the environment—particularly concerning where antiseptic-only protocols may inadvertently select for resistant organisms.
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Practical Takeaways
- •Chronic equine wounds treated only with antiseptics should be cultured and susceptibility tested, as biofilm-forming, antibiotic-resistant bacteria may develop without antibiotic therapy
- •Biofilm presence in infected equine wounds requires aggressive antimicrobial strategies; single-agent therapy may be inadequate, and higher antimicrobial concentrations or combination approaches may be necessary
- •Wound management protocols should include consideration of resistance transmission risks to handlers and the environment, emphasizing hygiene and appropriate antimicrobial stewardship
Key Findings
- •A 21-day-old equine chronic wound yielded three S. aureus isolates and one P. aeruginosa isolate, with the P. aeruginosa showing resistance to carbapenems and fluoroquinolones despite no prior antibiotic therapy
- •All four bacterial isolates (S. aureus and P. aeruginosa) demonstrated biofilm production capacity
- •Gentamicin at 10× MIC achieved the highest biofilm removal rate of 85.7% for P. aeruginosa and 59.3-78% for S. aureus isolates
- •Cross-resistance between antiseptics and antibiotics may occur in wound colonizers even without prior antibiotic exposure