Investigation of the important virulence genes and antibacterial sensitivity of escherichia coli strains isolated from mastitic cattle milk

In this study, isolation and identification of E. coli from mastitic cattle milk samples, detection of important virulence genes [Shiga toxin 1 (stx1), Shiga toxin 2 (stx2), heat sensitive toxin (lt), heat resistant toxin (st), invasive antigen locus (ial), intimin (eaeA), bundle pilus (bfpA), fimbrial antigen (aafII)] and antibiotic susceptibility profiles of isolates were aimed. In the study, 390 milk samples were taken from 328 mastitic milk samples in a special farm for one year. E. coli isolation was performed using conventional methods. Polymerase chain reaction (PCR) was used to confirm bacterial identification and identification of virulence genes. Sensitivities of ten isolates to ten antibiotics belonging to eight antimicrobial families were examined by disk diffusion method. In the study, E. coli was isolated and identified in 17.2% (67/390) of mastitis milk samples. Most prevalent virulence genes were stx1 (5/13=38.5%), stx2 (2/13=15.4%), st (2/13=15.4%), lt (1/13=7.7%), eaeA (3/13=23.1%); bfpA and aafII were not present in any isolate. 53.8% (7/13) of the isolates were identified as EHEC, 23.1% (3/13) as ETEC and 23.1% (3/13) as EPEC. It was determined that 89.5% (60/67), 37.3% (25/67), 35.8% (24/67) of isolates were resistant to chloramphenicol, ampicillin and tetracycline while antibiotic resistances for other 8 antibiotics varying between 2.9% and 22.3%, 3.0% (2/67) of the isolates were susceptible to all antibiotics used; 30.0% (20/67) were multiple resistant. Antimicrobial susceptibility should be monitored to detect changes in bacterial resistance profiles. Key Words: Escherichia coli, mastitis, antibiogram, virulence gene