Investigation of antimicrobial resistance and antimicrobial resistance genes in Staphylococcus aureus and coagulase-negative staphylococci isolated from rabbit.

Background and aim: Staphylococci, which inhabit skin and mucous membranes in humans and animals, are opportunistic pathogens. Coagulase-positive and coagulase-negative staphylococci (CoNS) are the two main groups. Clinical abscesses in rabbits often harbor Staphylococcus aureus and CoNS. This study estimated S. aureus and CoNS prevalence, resistance profiles, antimicrobial-resistant genes, and the accessory gene regulator (agr) group in rabbit clinical abscesses.

Materials and methods: Sixty-seven abscesses were gathered from 67 rabbits who visited Prasu-Arthorn Animal Hospital in Nakornpathom, Thailand, from January 2014 to October 2015. Thirty-four subcutaneous, 29 dental, 2 ocular, 1 mammary gland, and 1 uterine abscess were present. Conventional methods, including Gram staining, mannitol fermentation, hemolysis on blood agar, catalase testing, and coagulase production, identified and isolated S. aureus and CoNS from all abscesses. All S. aureus and CoNS isolates underwent antimicrobial susceptibility testing using the disk diffusion method. Polymerase chain reaction was used to detect the presence of blaZ, aacA-aphD, msrA, tetK, gyrA, grlA, dfrG, and cfr antimicrobial-resistant genes. Methicillin resistance was identified through the detection of a cefoxitin-resistant phenotype and the presence of mecA gene. Further investigation was conducted on the agr group of S. aureus isolates.

Results: In 67 abscesses, we found 19 S. aureus isolates in 9 abscesses (13.43%) and 37 CoNS isolates in 18 abscesses (26.87%), both majorly located at subcutaneous sites. About 59.46% of CoNS isolates were methicillin-resistant compared to 5.26% of S. aureus isolates. Methicillin-resistant S. aureus (MRSA) and methicillin-resistant CoNS (MRCoNS) both displayed multidrug resistance (MDR). Both MRSA and MRCoNS expressed multiple antimicrobial resistance genes, including blaZ, aacA-aphD, gyrA, grlA, msrA, tetK, and dfrG. Approximately 73.68% of the agr groups were agr I, 15.79% were agr III, and 10.53% were agr II.

Conclusion: This study found a high prevalence of MRCoNS with antimicrobial resistance and multiple antimicrobial-resistant genes in rabbits with clinical abscesses. The effectiveness of antibiotics against infections caused by such strains is a matter of concern. Owners should be educated about the importance of good hygiene practices and judicious antibiotic use to prevent widespread antimicrobial resistance.