EDTA potentiates gentamicin and ofloxacin antibacterial activity against biofilms of methicillin-resistant Staphylococcus pseudintermedius derived from canine superficial pyoderma.

Canine pyoderma often results from infections caused by methicillin-resistant Staphylococcus pseudintermedius (MRSP), which frequently exhibits multidrug resistance and potent biofilm-forming capabilities. Therefore, veterinary clinicians have limited effective antibiotic options. This study aimed to investigate the potential of ethylenediaminetetraacetic acid (EDTA) combined with antibiotics commonly used to treat canine pyoderma (gentamicin and ofloxacin) on MRSP biofilms in vitro. We performed in vitro biofilm survival assays to determine whether EDTA enhances the efficacy of gentamicin and ofloxacin against MRSP in biofilms. MRSP biofilms were cultured on polyvinyl chloride plates and exposed to high concentrations of gentamicin or ofloxacin. Survival rates varied among strains; however, ofloxacin proved to be more effective than gentamicin in reducing bacterial viability. Notably, some strains exposed to gentamicin showed survival rates exceeding 10%. Co-administration of EDTA with these antibiotics decreased MRSP survival in biofilms compared to antibiotic treatment alone, suggesting that EDTA augments the bactericidal activity of gentamicin and ofloxacin. This effect was particularly striking in antibiotic-tolerant strains, where the addition of EDTA markedly improved survival reduction beyond that achieved with antibiotics alone. These findings underscore the potential of EDTA as an adjunct treatment to enhance the effectiveness of antibiotics against MRSP-induced pyoderma.