Phenotypic and genotypic characterization of antimicrobial resistance in Escherichia coli isolates

Abstract

Background:The major influences on the increase and spread of antimicrobial resistant bacteria are the use of antimicrobial agents in human medicine and their use in livestock for therapy and growth promotion. To generate baseline data to use in future risk assessment of antimicrobial resistance, a number of surveillance program on the local, continental and global scale have been initiated. The prevalence of resistance in commensal E. coli is a good indicator for the selective pressure by antibiotics use and resistance problems to be expected in pathogenic bacteria. The aim of this study was to determine and compare the occurrence of antimicrobial resistance phenotypes and genotypes among E. coli strains recovered from animal sources.Methods & Materials: Fifty-eight (58) E. coli strains were isolated from animal sources (Cattle, pig and chicken). MIC was determined according to Clinical and Laboratory Standards Institute (CLSI) guidelines. Strains were screened and mapped by PCR methods for antimicrobial resistant genes, integrons and gene cassettes.Results: The resistance profile of E. coli for ampicillin (100%), cefotaxime (100%), ceftazidime (83%), ciprofloxacin (43%) (C), tetracycline (100%) (T), gentamicin (90%) (G), kanamycin (77%) (K), streptomycin (100%) (S), chloramphenicol (97%) (Ch) sulphamethoxazole (100%) (Su) and trimethoprime (97%) (T). Eight-Five per cent (85%) of E. coli harbored class 1 integron and variable gene cassettes were revealed. A prevalence of gene cassettes that present resistance to streptomycin and trimethoprime was observed. The resistance genes determinant present in gentamicin resistance were aac(3')-IIc, aac(6')-Ib and ant(2")-1a. The occurrence of aph(3)-Ia in kanamycin resistant strains was 68%. The prevalence of sul1 (80%) and sul2 (100%) was observed. The prevalence of tet(A) is higher than tet(B) in tetracycline-resistant strains. The gene determinants for chloramphenicol resistance (cat1 and catB) were detected. Differences in the rates and profile of resistance were observed, possibly reflecting differences in antibiotic use regimens among these strains.Conclusion: This study shows that multi-drug resistant E. coli isolates are prevalent in animal sources and a considerable proportion of E. coli strains are resistant to a variety of antimicrobial agents. Genotypic characterization revealed high number of diverse resistance determinants.http://dx.