Isolation, characterization and molecular evaluation of genetic factors of antibiotic resistance in pathogenic Escherichia coli

The usage of antimicrobial drugs in the veterinary field can cause the emergence, prevalence, and dissemination of antimicrobial resistance in bacteria isolated from food-producing animals. Antimicrobial drugs are essential for the treatment of bacterial infections in cattle. Class 1 integrons can extend antibiotic resistance genes among bacteria Escherichia coli from animal.The objective of this study was to investigate the antimicrobial resistance pattern and the frequency class 1 integrons Escherichia coli strains isolated from diarrheic calves in Fars province. A one hundred and twenty samples from 120 different diarrheic calves from Fars province in Iran were screened for the presence of virulence factors associated with diarrhea. Following isolation and identification of Escherichia coli strains on the basis of cultural, morphological and biochemical properties, the presence of various virulence genes of ETEC (k99, F41 fimbria and Sta), EHEC (Stx1, Stx2 and eae) was investigated by multiplex PCR. The isolates were examined for susceptibility to antimicrobial agent and class 1 integrons using PCR and agar disk-diffusion method for 8 antimicrobial agents. Out of 120 samples, 57 (47/5%) were found to be positive for Escherichia coli and 35 of them identified as pathogenic Escherichia coli including 21( 36/8%) and 14 (24/5%) ETEC and EHEC strains respectively. The most antibiotic resistance level was seen against erythromycin (100%), penicillin (100%) co-trimoxazole (100%), tetracycline (91/5%), ampicillin (88/5%) and chloramphenicol (83%). All isolates shown MDR . The study of molecular results showed that class 1 integron was detected in (48/75%) of isolates. Our data demonstrate the presence of MDR and class 1 integrons were common in Escherichia coli from calves in Fars province experiencing problems with neonatal diarrhea.