High Frequency of Class 2 and 3 Integrons Related to Drug-Resistance in Clinical Isolates of Diarrheagenic E. coli in Iran

Integrons are mobile genetic elements able to obtain the antibiotic resistance gene cassettes. The prevalence of integrons in the Enterobacteriaceae family has been varied and played an important role in the development of the drug resistant bacteria. The present study aimed to investigate the contribution of class 2 and 3 integrons in drug resistant Diarrheagenic Escherichia coli strains.
The 164 Diarrheagenic E. coli collected from feces samples of children in the Yasuj –Iran and all isolates were identified by standard biochemical tests. The antimicrobial susceptibility for 14 antibiotics, which are used conventionally was determined by disk diffusion. The presence of class 2 and 3 integrons in all isolates was investigated by PCR.
Of 164 E. coli isolates from children, 80.49% carried class 2 integron and the length of the amplicons ranged from 800 bp to 2 kb. Class 3 integrons were identified among 24 E. coli isolates. All the E.coli isolates were susceptible to imipenem and the greatest resistance was correspondent to nalidixic acid. A significant correlation was revealed between Class 2 integron and resistance to kanamycin, amikacin, gentamicin, ceftazidime, chloramphenicol and cephalexin. The presence of class 3 integron was significantly associated with resistance to ampicillin, gentamicin, streptomycin, kanamycin, tetracycline and trimetoprime-sulfametoxazol.
The results indicated that integrons are widespread in Diarrheagenic E. coli and its carriage contributed significantly to the emergence of resistance among Diarrheagenic E. coli. However, factors leading to the wide spread of integrons are still to be determined.