H Mita, T Kuroda, M Nomura, M Ohta
Biofilm formation at surgical sites should be considered following equine orthopedic surgery. In this in vitro study, povidone-iodine had greater activity than other agents against established biofilms, suggesting its potential usefulness for biofilm-associated surgical site disinfection.
BACKGROUND: Surgical site infection (SSI) is a serious complication of equine orthopedic surgery. Biofilm formation by the causative bacteria contributes to treatment failure by conferring tolerance to antimicrobial agents and disinfectants; however, data on biofilm formation and antiseptic or antimicrobial exposure in equine clinical isolates are limited.
AIMS/OBJECTIVES: Our objectives were to evaluate the biofilm-forming ability of bacterial strains isolated from postoperative equine orthopedic SSI and to assess the susceptibility of established biofilms to disinfectants and antimicrobial agents after short-term exposure.
METHODS: A total of 102 bacterial strains were evaluated. Biofilms were formed using a 96-well plate with a peg-lid system, and biofilm biomass was quantified spectrophotometrically. Biofilms were exposed for 10 min to five agents: povidone-iodine, chlorhexidine, benzalkonium chloride, gentamicin, and ampicillin. Viable bacteria were quantified by colony-forming unit counts, and effects were expressed as log reductions relative to controls.
RESULTS: Biofilm-forming ability varied among bacterial groups, with Acinetobacter spp. showing the highest optical density (1.68 ± 0.91) and methicillin-sensitive Staphylococcus aureus exhibiting lower values (0.12 ± 0.08). Povidone-iodine achieved a >5 log₁₀ CFU reduction across all bacterial groups. In Gram-negative bacteria, it achieved significantly greater reductions than chlorhexidine and benzalkonium chloride (1-3 log₁₀ CFU reduction). Antimicrobial agents showed little bactericidal activity against 24-h biofilms.
CONCLUSION: Biofilm formation at surgical sites should be considered following equine orthopedic surgery. In this in vitro study, povidone-iodine had greater activity than other agents against established biofilms, suggesting its potential usefulness for biofilm-associated surgical site disinfection.