Molecular surveillance of putative virulence factors and antibiotic resistance in staphyloccus aureus isolates recovered from intra-mammary infections of river buffalo



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Microbial Pathogenesis






In dairy and healthcare surroundings, Staphylococcus aureus has been documented as a leading pathogen. Prevalence of drugs resistant strains in mastitic ruminants is another serious problem. To elucidate the antibiotic-resistant and virulence gene patterns,S. aureus isolates (111) were recovered from intra-mammary infections suffering buffaloes, and characterized using PCR and disk diffusion assays. The pathogenic factors were associated with antibiotic-resistant patterns and analyzed. Molecular and phenotypic characterization of tested isolates showed significantly resistance to tetracycline, macrolides, lincosamides and aminoglycosides. MecA gene was detected in 5.4% of isolates of S. aureus. The isolates showed variation in expression of pathogenic factors. Coagulase genotype VI showed high antibiotics susceptibility while patterns I, III, IV and V belonged to resistant category of tested bacterial population. The prevalence of other virulent genes namely, Ebp, Fib, FnbB, Bbp and Map were present significantly in highly pathogenic isolates. The isolates (41.4%) were found positive for super-antigen enterotoxins Sec, See, Seg and Sei genes only and predominated in methicillin-susceptible compared to resistant ones. The allelic variants of Agr-1 and 3 were considerably associated with coagulase genotypes and other virulence factors, while the enterotoxins were found considerably associated with Agr-1 and 2. Distribution of virulent genes between methicillin-susceptible and resistant isolates was uneven. The distribution of high pathogenic characteristic in antibiotic-susceptible isolates indicated that these were equally responsible in maintaining the intra-mammary infections in animals and cannot be overlooked.

The surveillance of pathogenic and antibiotics resistance factors of isolates revealed that certain genetic elements were over producing (Ebp, Fib, FnbB, Bbp, Map, TetK, MsrB, AacA-D) in mastitic S. aureus isolates especially from clinical cases. This outcome or genetic frame of S. aureus isolates may be further use for culling or segregation of animals infected with harmful strains to reduce the dissemination of pathogenic microorganisms or containment of mastitis.