Molecular Prevalence and Antimicrobial Resistance Patterns of Methicillin-Resistant Staphylococcus aureus in...

Methicillin-resistant Staphylococcus aureus (MRSA) is an emerging zoonotic pathogen in livestock and poses a potential public health threat.

This cross-sectional study investigated the prevalence, antimicrobial resistance profiles and molecular characteristics of S. aureus and MRSA isolated from buffalo nasal swabs in the Sylhet and Noakhali districts of Bangladesh.

A total of 400 nasal swabs were collected and screened using selective culture and biochemical tests, followed by PCR targeting the nuc gene for S. aureus and the mecA gene for MRSA. Antimicrobial susceptibility testing (AST) was conducted using disk diffusion as per the Clinical and Laboratory Standards Institute (CLSI) 2020 standard.

Overall, 78 isolates (19.5%; 95% CI: 15.7-23.7) were confirmed as S. aureus, of which 43 (10.5%; 95% CI: 7.7-13.9) were identified as MRSA. Higher MRSA prevalence was observed in buffaloes aged 1-3 years (14.1%), males (14.8%; p = 0.01) and animals with respiratory symptoms (25.2%) compared to healthy buffaloes (4.3%; p < 0.001). AST of MRSA isolates showed high resistance to cefoxitin (97.7%), ceftriaxone (86.0%) and tetracycline (65.1%), whereas resistance to ciprofloxacin (4.7%) and levofloxacin (9.3%) was low. Multidrug resistance was detected in 88.4% (95% CI: 74.9-96.1) of MRSA isolates, with multiple antibiotic resistance index (MARI) values ranging from 0.23 to 0.54. Virulence genes (sea, hla and icaA) and resistance genes (aac(3)-IV, sul1, tetA and strA) were detected.

These findings indicate a substantial MRSA burden in buffaloes, emphasizing the need for prudent antibiotic use and ongoing surveillance to reduce zoonotic transmission risks.