Prevalence of neonatal calf diarrhea caused by Escherichia coli and investigation of virulence factors, serotypes, and antibiotic susceptibility.

Neonatal calf diarrhea (NCD) is one of the most important concerns in cattle production. Escherichia coli is the most important bacterial agent of NCD. Although vaccination and antibiotic treatment are common in NCD, the high antigenic diversity of E. coli and the increase in antibiotic resistance cause difficulties in the control. The study aimed to investigate the rate of E. coli in calf diarrhea, isolate an agent of the NCD E. coli strain, determine antimicrobial resistance, and find out about some surface antigens. Fecal samples (n=115) were analyzed to isolate pathogenic E. coli strains with nine mixed infections; sixty-one strains isolate from fifty diarrhoeic calves. Among the isolates from diseased animals, 22 K99+STa+F41, 3 K99+STa, 3 strains F41, 2 strains Stx1, one strain K99, one strain eae, and one strain Stx2+eae were detected. 27 strains of F17- associated fimbriae have been identified. 17 strains F17a, 6 strains F111, 3 strains F17c, one strain carrying the F17a and F17c gene regions, whereas subfamily typing of one strain could not be performed. Serotypes were determined by molecular and serological methods: 32/61 (52.5%) isolates were O101 and 2/61 (3.3%) isolates were O9 serotypes. But 27 strain serotypes could not be detected. The antibiotic resistance profiles of the isolates were determined by the disc diffusion method. The resistance rates to antibiotics were trimethoprim- sulphamethoxazole 91.7%, ampicillin 86.7%, enrofloxacin 86.7%, gentamicin 45%, tobramycin 41.7%, cefotaxime 3.3%, and ceftazidime 1.7%. Due to increasing antibiotic resistance, prophylaxis is gaining importance. In further research, E. coli surface antigenic structures should be examined in detail, and it should form the basis for vaccine and hyperimmunization studies to be developed.