Methicillin-resistant (MRSA) associated with mastitis among water buffaloes in the Philippines.

Methicillin-resistant (MRSA) from dairy animals could pose a public health concern in the population. The study was designed to determine the prevalence of and MRSA associated with mastitis among water buffaloes in the central part of Luzon island, the Philippines, and to investigate its associated factors. Three hundred and eighty-four water buffaloes were examined for mastitis using California mastitis test (CMT). Composite milk samples (n = 93) were collected from buffaloes showing positive reaction with CMT. was identified from milk samples using biochemical tests. Cefoxitin disk diffusion assay and PCR detecting gene were performed to identify MRSA isolates. Disk diffusion assay was used to investigate the antimicrobial resistance against 9 antibiotics. The prevalence of was 41.94% (39/93) MRSA isolates resistant to cefoxitin were at 25.81% (24/93) but only 37.5% (9/24) harbored the gene. All 24 MRSA isolates were resistant to penicillin while the majority were susceptible to clindamycin, trimethoprim-sulfamethoxazole, gentamycin, tetracycline, rifampicin, ciprofloxacin and chloramphenicol with intermediate susceptibility to erythromycin. Furthermore, 37.5% of the isolates were found resistant to two or more antibiotics. Animal-level factor associated with MRSA infection was the history of mastitis (OR = 3.18, CI = 1.03-9.79, p = 0.040). Herd-level factors associated with the detection of MRSA in milk included herd size (OR = 4.24, CI = 1.05-17.07, p = 0.042) and the presence of other animals (OR = 0.15, CI = 0.04-0.58, p = 0.006). High prevalence of intramammary infection with and MRSA in dairy buffaloes was observed in the region. This finding raises the concern of preventing zoonotic spread of MRSA.