# Characterization of Extended-Spectrum β-Lactamase-Producing Escherichia coli in Animal Farms in Hunan Province, China

## TL;DR

This study examines antibiotic-resistant Escherichia coli in animal farms in China and finds high resistance to common antibiotics, with potential risks to human health.

## Contribution

The study characterizes ESBL-producing E. coli in animal farms in Hunan Province, identifying resistance patterns and genetic subtypes.

## Key findings

- 6.66% of fecal samples tested positive for ESBL-producing Escherichia coli.
- The most common ESBL genotype was blaCTX-M-55, and the predominant plasmid type was IncFIB.
- ESBL-EC isolates showed resistance to cefotaxime, tetracycline, and trimethoprim-sulfamethoxazole but remained susceptible to meropenem.

## Abstract

Multi-drug resistance of bacteria producing extended-spectrum β-lactamase (ESBL) is a public health challenge. Thus, this study aimed to investigate the antimicrobial susceptibility of ESBL-producing Escherichia coli (ESBL-EC) in Hunan Province, China. A total of 1366 fecal samples were collected from pig, chicken, and cattle farms over a six-year period, which were assessed using strain isolation, 16S rRNA identification, polymerase chain reaction, drug sensitivity testing, whole-genome sequencing, and bioinformatics analysis. The results showed an overall prevalence of 6.66% for ESBL-EC strains, with ESBL positivity extents for pigs, chickens, and cattle isolates at 6.77%, 6.54%, and 12.5%, respectively. Most ESBL-EC isolates were resistant to cefotaxime, tetracycline, and trimethoprim-sulfamethoxazole; however, all the isolates were susceptible to meropenem, with relatively low resistance to amikacin and tigecycline. Various multi-locus sequence types with different origins and similar affinities were identified, with ST155 (n = 16) being the most common subtype. Several types of resistance genes were identified among the 91 positive strains, with beta-lactamase blaCTX-M-55 being the most common ESBL genotype. IncFIB was the predominant plasmid type. Widespread use of antibiotics in animal farming may increase antibiotic resistance, posing a serious threat to the health of farmed animals and, thus, to human food security and health.