Methicillin-resistant coagulase-negative staphylococci isolated from healthy horses in Japan

Abstract

Objective - To determine patterns of methicillin-resistant staphylococci isolated from apparently healthy horses. Sample Population - 44 horses from 8 riding clubs in Japan. Procedure - Methicillin-resistant staphylococci were isolated from the skin or nares, using a selective medium containing a β-(symboric) lactam antibiotic, ceftizoxime. Clonality of isolates was determined by use of pulsed-field gel electrophoresis. Detection of mecA, mecl, and mecR1 genes was accomplished by use of polymerase chain reactions. Result - Of the 44 horses, 13 (29.5%) yielded 15 isolates of methicillin-resistant staphylococci. The 15 isolates were identified as 6 species (Staphylococcus epidermidis, S lentus, S saprophyticus, S xylosus, S sciuri, and S haemolyticus). However, methicillin-resistant S aureus was seldom isolated. Each isolate contained the mecA gene and had a high resistance to β- lactam antibiotics. Some isolates also were resistant to other antibiotics such as erythromycin and kanamycin. Conclusions and Clinical Relevance - Methicillin-resistant coagulase-negative staphylococci that were highly resistant to various antibiotics were isolated from apparently healthy horses in Japan. These organisms must be considered a potential threat to horses and veterinarians who care for them.