LAUSR

PurposeThe aims of the current study were to investigate the frequency and genetic diversity of Staphylococcus aureus from healthy horses, including both methicillin-resistant (MRSA) and -susceptible S. aureus (MSSA).MethodsThree hundred-one nasal swabs were collected from healthy horses in three provinces, Iran. Sixty-one of the 301 tested samples contained S. aureus (20.3%), among which five were MRSA. Isolates were typed by spa PCR-RFLP and agr typing, followed by sequence-based spa typing and MLST on representative strains from each restriction pattern and SCCmec typing for MRSA strains. The presence of Panton-Valentine Leukocidin (PVL) encoding genes was also tested using PCR.ResultsEight distinct RFLP patterns (designated as N1-N8) were observed, with N2 (23/61; 37.7%) and N4 (18/61; 29.5%) the most common. On sequencing, N1-N8 patterns were found to be of clonal types ST15-t084, ST2151-t2484, ST291-t937, ST1-t127, and ST1-t1383, ST700-t11926, ST133-t1166, and ST1278-t12595, respectively. No PVL-positive S. aureus were detected. Five MRSA were identified as ST2151-t2484-SCCmecIVa (2 isolates), ST15-t084-SCCmecIVa, ST1-t1383-SCCmecIVa, and t12595-SCCmecIVa (one isolate each). Majority of S. aureus isolates were ascribed to agr types III (n = 30; 49.2%) and IV (n = 28; 45.9%), followed by types II (n = 2, 3.3%) and I (n = 1, 1.6%). The carriage of S. aureus was found to be associated with geographic locations.ConclusionsThis study for the first time describes the circulation of diverse clones of MSSA and MRSA among the Iranian horse population. This may pose a public health risk, which supports the need for their epidemiological monitoring.