prevalence of extended-spectrum ß-lactamase-producing escherichia coli in agricultural fields of gorgan district using bovine manure

the aim of this study was to assess the prevalence of esbl-producing e. coli in agricultural fields of gorgan district, golestan province. soil samples were collected from 20 agricultural fields, half of them treated with chemical fertilizers and the rest with bovine manure. two samples, from surface and a depth of 15cm, were taken. after enrichment and culture onto macconkey agar, pink colored colonies were examined for escherichia coli. the cefotaxime resistant e. coli were examined by phenotypic confirmatory tests. then, antibiotic susceptibility of the confirmed esbl-producing e. coli strains was determined. the results of this study showed that the prevalence of e. coli in the manure-amended soils were higher than the soils enriched with chemical fertilizers. moreover, e. coli strains in the depth samples were more than the surface samples. about %53.1 of the strains isolated from the manure-amended soils were resistant to cefotaxime and the %43 of them were positive for esbl. meanwhile, %33.3 of the strains isolated from the soils treated with chemical fertilizers were resistant to cefotaxime in which %75 of them were esbl producers. the highest resistance rate was observed against amoxicillin in all the esbl-producing isolates. the results of this study showed that the use of animal manure may increases the dissemination of the antibiotic resistant bacteria to the soil. this may transfer antibiotic-resistant genes to other bacteria, causing spreading of these genes in the environment.