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

Objective-To determine patterns of methicillin-resistant staphylococci isol ated from apparently healthy horses. Sample Population-44 horses from 8 riding clubs in Japan. Procedure-Methicillin-resistant staphylococci were isolated from the skin o r nares, using a selective medium containing a beta-(symboric) lactam antib iotic, ceftizoxime. Clonality of isolates was determined by use of pulsed-f ield gel electrophoresis. Detection of mecA, mecl, and mecR1 genes was acco mplished by use of polymerase chain reactions. Result-Of the 44 horses, 13 (29.5%) yielded 15 isolates of methicillin-resi stant staphylococci. The 15 isolates were identified as 6 species (Staphylo coccus epidermidis, S lentus, S saprophyticus, S xylosus, S sciuri, and S h aemolyticus). However, methicillin-resistant S aureus was seldom isolated. Each isolate contained the mecA gene and had a high resistance to beta- lac tam antibiotics. Some isolates also were resistant to other antibiotics suc h as erythromycin and kanamycin. Conclusions and Clinical Relevance-Methicillin-resistant coagulase-negative staphylococci that were highly resistant to various antibiotics were isola ted from apparently healthy horses in Japan. These organisms must be consid ered a potential threat to horses and veterinarians who care for them.