Clonality and Antimicrobial Susceptibility of Staphylococcus aureus and Methicillin-Resistant S. aureus Isolates from Food Animals and Other Animals

cus aureus positive. Prevalence of methicillin-resistant S. aureus (MRSA) was high in pigs (animals, 21.3%; batches, 46.5%), with all MRSA isolates and most methicillin-sensitive S. aureus isolates belonging to clonal complex 9 (CC9) and being multidrug resistant. The predominant S. aureus CCs among dog and cat isolates were similar. Among rodent isolates, CC398 predomi-nated, with spa t034 the most frequent spa type detected. Staphylococcus aureus is a major pathogen in human and veter-inary medicine (3, 4, 14). Since 2005, there has been a marked increase in methicillin-resistant S. aureus (MRSA) among farm animals, especially pigs (14). These MRSA isolates belong to spe-cific clones (sequence type 9 [ST9] and ST398) and are often re-sistant to other non--lactam antibiotics (14). However, limited studies have been performed to compare the clonal structures of methicillin-sensitive S. aureus (MSSA) and MRSA populations in food animals and other animals. Here, we investigated the preva-lence of MRSA and MSSA among various animals and the strains were characterized by molecular methods. From September 2008 to August 2011, nasal or tracheal swabs were obtained from ani