Antimicrobial resistance patterns in Escherichia coli of poultry origin in the Kandy district

Abstract

Infection by pathogenic Escherichia coli causes considerable economic losses in the poultry industry and the emergence of drug resistance in this pathogen due to indiscriminate use of antimicrobials in commercial poultry farming is a major concern. This study was conducted to compare antimicrobial resistance patterns among E. coli isolates from commercial and backyard poultry farms, as we predicted that irrational use of antimicrobials increases the occurrence of drug resistant strains of E. coli in commercial layers.

Ten commercial layer farms in the Kandy district were selected as the test group and five backyard poultry farms were used as the control group. Composite faecal and litter samples were collected from layer farms, and composite faecal samples were collected from backyard poultry farms. Antimicrobial sensitivity tests were carried out on E. coli isolates from these samples against enrofloxacin, amoxicillin, neomycin, tetracycline and sulphamethoxazole-trimethoprim. Fisher’s exact test was used to test for an association between the occurrence of antimicrobial resistance and poultry management system. Of the test group, 90% of faecal isolates and 30% of litter isolates were resistant to at least one of the antimicrobials tested. Faecal isolates from layer farms were resistant to all antimicrobials tested except enrofloxacin while the control group was only resistant to neomycin (60% of samples). Apparent multidrug resistance was observed in faecal E. coli isolates in the test group but not in backyard poultry, with 60% of layer faecal isolates being resistant to two or more antimicrobials. Of the litter isolates, 20% showed apparent multidrug resistance. There was a significant association between the occurrence of tetracycline resistance in E. coli and the type of poultry management system (P = 0.03).

According to information obtained from farmers, factors that may predispose to the development of drug resistance were use of antimicrobials without professional advice, prolonged use of prophylactic antimicrobials, poor litter management and improper biosecurity measures. This study indicates that measures should be undertaken to ensure the rational use of antimicrobials in the commercial poultry industry in order to prevent the emergence of antimicrobial resistance.