On-farm epidemiology and phylogenetic evaluation of methicillin and beta-lactam-resistant Staphylococcus aureus isolated from dairy cattle and buffaloes with endometritis

Background: Staphylococcus aureus is a potential emerging and prevailing multidrug-resistant (MDR) pathogen involved in bovine endometritis. Aims: Present research evaluated the prevalence and molecular characterization of methicillin-resistant S. aureus (MRSA) and beta-lactam resistant S. aureus (BRSA) and also analyzed the associated risk factors with endometritis along with antibiotic resistance patterns. Methods: A total of 384 uterine and vaginal fluid samples were collected from the adult dairy cattle and buffaloes showing the clinical signs of endometritis including foul-smelling vaginal discharge, fever, enlarged and thickened uterine horns on rectal palpation, and confirmation by ultrasonography findings. The collected samples were subjected to standard microbiological methods for the detection of S. aureus. The confirmed isolates were further subjected to the Kirby-Bauer disc diffusion test and the detection of the mecA and blaZ genes for the confirmation of MRSA and BRSA. Results: Study found an overall prevalence of 17.96% for S. aureus from bovine endometritis cases. Among S. aureus isolates, 50.72% and 37.68% isolates were confirmed MRSA while BRSA was found as 36.23% and 18.84%, based on phenotypic and genotypic methods, respectively. Phylogenetic analysis indicated the possibility of pathogen transmission within and between livestock animals. Risk factor analysis showed that the breed of animal, visible discharge from vagina, lactation number, insemination procedure, and calving place showed significant (P<0.05) association with S. aureus-associated endometritis. Antimicrobial susceptibility testing of study isolates showed the resistance to various commonly used antibiotics. Conclusion: The study concluded that S. aureus is found in 17.96% of bovines affected with endometritis and require further intensive research to elucidate the farm economic losses.