Molecular identification, antimicrobial resistance and virulence gene profiling of spp. associated with bovine sub-clinical mastitis in Bangladesh.

This study was conducted to investigate the diversity and antimicrobial resistance profiling of species causing sub-clinical mastitis (SCM) in dairy herds in Bangladesh as well as putative risk factors associated with the infections. Individual quarter milk samples were collected from a total of 284 lactating cows from 30 dairy farms were screened by means of California mastitis test; 178 (62.7%) of them had at least of quarter affected by SCM. After conventional microbiological isolation procedures, PCR tests were used for species identification and detection of antimicrobial resistance and virulence genes. (65.7%) was the most predominant species followed by, (20.2%), (19.1%), (15.7%), and (5.6%). High levels of antimicrobial resistance to ampicillin and amoxicillin/clavulanic acid were observed in (82.1% and 75%) and (80% and 70%), while resistance to cefepime was markedly higher in (95.7%), (94.1%) and (97.2%). Multidrug resistance isolates were identified in all five species. The A gene was detected in (32.1%) and (5.98%). In addition, 20% and 17.7% carried the cytotoxin () gene, while 14.3% harbored the toxic shock syndrome toxin () gene. Multivariable logistic regression analysis identified "Old aged" (OR [CI]: 3.5 [1-12.4]); "Early stage of lactation" (OR [CI]: 3.4 [1.2-9.7]) and, "Firm udder condition" (OR [CI]: 4.2 [1.2-14.6]) as risk factors associated with SCM caused by , and , respectively. Moreover, "Use of antimicrobials" (OR [CI]: 10.4 [3.4-32.1] and "History of previous clinical mastitis" (OR [CI]: 4.9 [1.2-19.7] for the carriage of methicillin-resistant spp.