Molecular Identification and Antimicrobial Resistance Patterns of Bacteria Isolated from Bovine Mastitis in Urban and Peri-urban Dairy Farms

Background: Mastitis is a frequently occurring disease in cattle, generating significant economic losses to the dairy industry. Milk produced from mastitis affected cows has a potential to disseminate antimicrobial resistance (AMR), which induces public health risks. Therefore, the present study was intended to perform molecular characterization and AMR profiling for pathogens isolated from mastitis milk of dairy cows in Chhattisgarh, a densely dairy-populated state in central India. Methods: PacBio SMART sequencing technology was applied for identification of mastitis causing pathogens through full length 16S rRNA gene sequencing. Phenotypic AMR profiling of these pathogens was performed through antimicrobial susceptibility testing and molecular profiling through PCR assay by determining antibiotic resistance genes. Result: Molecular identification of 125 bacterial isolates represented 37 species of pathogens that cause mastitis in dairy cattle. Among these, prevalent pathogens were identified as Escherichia coli (19.2%), Enterobacter cloacae (8.8%), Klebsiella pneumoniae (7.2%) and Staphylococcus chromogenes (6.4%). Pathogens showed a high degree of resistance to cefixime (87.2%) followed by cefotaxime (82.4%), ciprofloxacin (68.8%), ceftriaxone (65.6%) and amikacin (52.8%) antibiotics. In total, 94 out of 125 bacterial isolates emerged as multidrug-resistant. Antibiotic resistant genes profiling revealed the existence of extended-spectrum beta-lactamase genes viz. blaTEM, blaZ, blaNDM1 and blaNDM2 among the multidrug-resistant pathogens. Our findings delineated the growing resistance to beta-lactam antibiotics among the milk-borne pathogens in central India and therefore, it suggests an urgent need to combat transmission of AMR through the dairy food chain.