Antimicrobial resistance and occurrence of indicator and pathogenic bacteria in organic and conventional chicken meat: comparative study

Abstract

The aim of this study was to comparatively assess the occurrence of pathogenic and indicator bacteria, and the antimicrobial resistance of Enterobacteriaceae, isolated from organic and conventional chicken carcasses. Fifty frozen chickens were assessed from five different commercial brands purchased at retail stores in the South and Southeast regions of Brazil. Of these chickens, 25 were conventionally farmed and 25 were organically farmed. Mesophilic and psychrotrophic counts were made, as well as counts for total coliform, Escherichia coli, coagulase-positive Staphylococcus and the assessment of Salmonella sp. Antimicrobial resistance was evaluated using the disk diffusion method. The results were statistically analyzed by ANOVA, and Tukey´s test was used to compare means between brands within the organic and conventional groups. The Kolmogorov-Smirnov test was used to compare bacterial counts between organic and conventional group. Differences of antimicrobial resistance between groups were calculated using the Chi square test (P<0.05). The organic chicken carcasses showed higher microbiological contamination (P<0.05) compared to conventional carcasses; however, Enterobacteriaceae from the organic chicken showed lower antimicrobial resistance. The highest frequency of resistance in Enterobacteriaceae isolated from both organic and conventional chicken was tetracycline. The restricted use or absence of antibiotics in organic farming practices can lower the risk of dissemination of antibiotic resistant bacteria when chicken is consumed.

Keywords

• Antimicrobial resistance
• Microbiological contamination
• Organic chicken