# Prospective Study of the Relative Abundance of Antimicrobial Resistance Genes in Escherichia coli O157:H7 Obtained from Chicken Carcasses from Local Markets in Lima, Peru

## TL;DR

This study found that chicken carcasses in Lima, Peru, carry E. coli O157:H7 and antimicrobial resistance genes, with higher bacterial loads and gene abundance in enclosed markets.

## Contribution

The study provides new evidence of the association between E. coli load and ARG abundance in chicken carcasses from different market types in Peru.

## Key findings

- E. coli O157:H7 was detected in 76.9% and 86.6% of samples from enclosed and open markets, respectively.
- Bacterial load was higher in enclosed markets compared to open markets.
- A strong positive correlation was found between E. coli load and ARG abundance, especially in enclosed markets.

## Abstract

Objective: This study addresses antimicrobial resistance (AMR), a growing public health threat, by evaluating the role of chicken carcasses as possible vehicle for the spread of Escherichia coli O157:H7 and antimicrobial resistance genes (ARGs), with the aim of analyzing the association between bacterial load and the relative abundance of ARGs in samples obtained from an open and an enclosed market in Lima, Peru. Methods: SYBR Green qPCR was used to analyze 28 chicken carcasses from two local markets in the Lima metropolitan area (Enclosed market n = 13, and Open Market n = 15), detecting Escherichia coli O157:H7 and ARGs like blaCTX-M, blaTEM, and strA. Results: The bacterial load was higher in the enclosed market (5.062 log CFU/mL) than in the open market (3.875 log CFU/mL). E. coli O157:H7 was detected in 76.9% and 86.6% of samples, with average loads of 1.676 and 1.251 log CFU/mL, respectively. The relative abundance of blaCTX-M and blaTEM showed greater dispersion in the open market, whereas strA was more homogeneous in both markets. Significant positive correlation was found between E. coli load and ARGs abundance, stronger in the enclosed market (r = 0.904–0.945) and moderate to high in the open market (r = 0.794–0.920). Conclusions: The results demonstrate a significant correlation between E. coli O157:H7 load and ARGs, highlighting the need for a comprehensive approach within the framework of the “OneHealth” initiative.