Occurrence of genes associated with virulence in Escherichia coli isolates from chicken carcasses at different stages of processing at a slaughterhouse

Escherichia coli is a bacterium frequently found in chicken carcasses, causing carcass condemnation with losses to the industry and when present in food, it carries a risk to public health as there is evidence that some strains pathogenic to birds (APEC - Avian Pathogenic E. coli) have zoonotic potential. Carcass contamination can occur at the slaughterhouse, but the influence of the different stages of processing in the selection of potential extraintestinal pathogenic E. coli strains is unknown. This study aimed to analyze the influence of the processing steps in the slaughterhouse on the detection of E. coli isolates carrying APEC predictor's virulence-associated genes (VAGs), and to relate their presence with post-mortem condemnation. A sample consisted of four pooled carcasses collected at seven different stages of slaughter (before scalding, after scalding, after plucking, before evisceration/after shower wash, after evisceration, after pre-coolers, and after packing) from 15 batches of broilers. The total samples obtained was 105 pools with four carcasses each, totaling 420 carcasses analyzed. Enterobacteriaceae were counted from each pool and E. coli were subsequently selected, which were submitted to pentaplex PCR to identify the five VAG APEC predictor's: iroN, ompT, hlyF, iss, and iutA. The Enterobacteriaceae count demonstrated a reduction of 4.25 log CFU per gram of carcass from the first to the last stage analyzed, with scalding and pre-cooling by immersion being the procedures that contributed most to this reduction. The presence of VAGs and potential APEC (presence of two or more of these gene predictors) was observed at all points evaluated in the slaughterhouse, which suggested that bacteria carrying these genes could reach the consumer.

Automated summary

This study analyzed the impact of different processing stages in the slaughterhouse on the detection of E. coli isolates carrying APEC predictor's virulence-associated genes, finding that scalding and pre-cooling procedures contributed most to reducing bacterial count. The presence of VAGs and potential APEC was observed at all points evaluated in the slaughterhouse, suggesting the potential transmission of bacteria carrying these genes to consumers.