No abstract

Coagulase positive Staphylococci (CoPS) are the leading cause of canine cutaneous and otic infections. Virulence factors associated with Staphylococci include the expression of mec and panton-valentine leukocidin (pvl) genes. Methicillin-resistance (MR) is commonly associated with mecA gene expression, although a recently identified variant, mecC, has been reported. This study aims to evaluate the prevalence of mecA, mecC and pvl genes in 232 clinical isolates of CoPS collected from dogs with pyoderma. A multiplex PCR, and Kirby-Bauer disk diffusion susceptibility test for cefoxitin was performed for all isolates. PBP2a agglutination test was performed on 127 isolates. Standard MRSA isolates were used as positive controls. The mecA gene was identified in 149/232 isolates (64.2%): 116 S. pseudintermedius, 30 S. coagulans and three S. aureus. The pvl gene was present in only 1 isolate of S. pseudintermedius (0.4%), whereas no isolates carried the mecC gene. 34 isolates were resistant to cefoxitin (14.6%) and they were all mecA positive. The results of this study show an MR prevalence of 64.2% confirming concerns about antibiotic resistance in veterinary medicine. In conclusion, this is the first study analyzing the prevalence of mecC and pvl in comparison to mecA, in a large cohort of CoPS clinical isolates from dogs with pyoderma. A multimodal surveillance on the prevalence of mecC and pvl in veterinary medicine is essential to appropriate antimicrobial management.

Background -Because of the increased incidence of multidrug-resistant (MDR) bacteria, the use of disinfectants over antibiotics has been encouraged. However, the interactions between disinfectants and host local immunity are poorly understood.Objective -To assess the effects of chlorhexidine digluconate (Chx), with and without selected host defence peptides (HDPs), against MDR Staphylococcus pseudintermedius (MDR-SP).Methods and materials -Ten clinical isolates of MDR-SP were tested, using a modified microbroth dilution method. Four two-fold dilutions of 2% Chx and 1 lg/mL the HDPs synthetic canine b-defensin 103 (cBD103) or cathelicidin (cCath) were tested alone or in combination. Colony counts after 5, 15, 30 and 60 min, and a minimum inhibitory concentration (MIC) after 24 h were recorded. Friedman followed by Dunn's multiple comparison tests with significance of P < 0.05 were used for statistical analysis. Synergy, additivity/neutrality or antagonism were calculated.Results -Growth was not inhibited by either HDP alone. An MIC of 0.312 lg/mL Chx was achieved for nine of the isolates. One isolate had an MIC of 0.078 lg/mL Chx. A MIC 90 (in nine of 10 isolates) of 0.312 µg/mL was seen for Chx in combination with either HDP. Synergy was seen in the combination Chx/cCath used at the highest concentrations of Chx (0.624 µg/mL and 0.312 µg/mL) after 30 and 60 min incubation. Additivity/neutrality was seen for most of the other concentrations and times of incubation.Conclusions and clinical importance -These results suggest a synergistic/additive effect between Chx and HDPs in dogs. Further studies evaluating the mechanisms behind this effect are needed.

Biofilm has been recognized as an important source of antimicrobial resistance. These sessile microbial colonies tend to attach and grow on every surface, biotic and abiotic, and they account for approximately 80% of chronic and recurrent infections.