# Genetic diversity with potential ESBL-producing and multidrug-resistant Salmonella strains from chicken meat

## TL;DR

This study analyzed Salmonella strains from chicken meat in Istanbul and found high levels of antibiotic resistance and genetic diversity.

## Contribution

The study provides a comprehensive analysis of ESBL-producing and multidrug-resistant Salmonella strains from chicken meat in Istanbul.

## Key findings

- S. Infantis was the dominant Salmonella type found in chicken meat samples.
- High resistance rates were observed for pefloxacin, azithromycin, and tetracycline.
- Multidrug resistance was identified in 84.6% of the Salmonella strains.

## Abstract

Salmonella, a major foodborne pathogen, is a primary concern due to its role in spreading antibiotic resistance. Raw chicken meat samples (n = 210) were collected from various retail locations in Istanbul.

The food samples were isolated according to ISO 6579-1 and 13 (6.2%) of Salmonella strains confirmed through PCR, agglutination tests, and Sanger sequencing; S. Infantis (84.6%) was identified as the dominant type. The other types found included S. Enteritidis (7.7%) and S. Virchow (7.7%). Additionally, antibiotic susceptibility was tested according to EUCAST and CLSI standards in different Salmonella serotypes. The serotypes were analyzed for susceptibility to 13 antibiotics using agar-disk diffusion assays, and resistance levels were determined via E-test.

The disc diffusion method revealed resistance to cefazolin across all Salmonella serotypes. High resistance rates were also observed for pefloxacin (84.6%), azithromycin (76.9%), and tetracycline (84.6%). Multidrug resistance was identified in 11 (84.6%) strains by the disc diffusion test. The minimum inhibitory concentration testing with MIC test strips showed high tetracycline resistance at 84.6%. The blaTEM gene was found in 30.7% of strains, while blaCTX-M subgroup 1 (7.7%) and blaCTX-M subgroup 9 (30%) were detected by multiplex PCR; however, and blaCTX-M, blaOXA-2, and blaSHV genes were not present. Resistance to carbapenem and colistin was also checked via PCR, and blaOXA-48, blaVIM, blaNDM, blaKPC, and mcr genes were not detected in the Salmonella serotypes.

This pioneering study provides a comprehensive analysis of serotyping and ESBL production in Salmonella strains isolated from Istanbul.