The character of multidrug-resistant methicillin-resistant Staphylococcus aureus (MRSA) isolated from a subtropical river and its tributaries contaminated by the nearby livestock industry

The Methicillin-resistant<i> Staphylococcus aureus</i> (MRSA) is a major health threat that can cause infections in hospitals, communities, and animal husbandry areas. The subtropical river basin of the Puzih River in Taiwan is the confluence of river branches flowing through agricultural settlements containing farmlands and animal husbandry areas. A typical LA-MRSA is SCCmec IV or V, either of which lacks the Panton–Valentine leukocidin (PVL) gene but has broad variable patterns of antimicrobial susceptibility. This study aimed to determine the existence of MRSA in the Puzih River and to investigate multidrug resistance and SCCmec typing to explore possible routes of transmission. Our results revealed that the detection rate (7.8%) for MRSA in the suburban livestock intensive areas was higher than for other Puzih River areas. The ratio for multidrug-resistant (MDR) MRSA against all isolates was 76.9% (30/39). Major MDR isolates (66.7%) exhibited resistance to chloramphenicol, ciprofloxacin, clindamycin, erythromycin, sulfamethoxazole-trimethoprim, and tetracycline. Moreover, diversity in MDR patterns was higher in MRSA isolates from downtown and suburban livestock intensive areas than in other Puzih River areas. The majority of MRSA isolates (64.1%) in this study possessed SCCmec type IV without the existence of PVL, which is a typical characteristic of LA-MRSA. The enterobacterial repetitive intergenic consensus PCR (ERIC-PCR) typing method provided a method to distinguish SCCmec types of MRSA isolates and was advantageous for discriminating the diversity of resistance patterns. This study thus highlights the potential threat posed by highly drug-resistant LA-MRSA to human health through waterborne transmission.<br>