Molecular serotyping of Salmonella strains isolated from retail chicken meats by in silico derived multiplex PCR, determination of ESBL, and colistin resistance genes mcr-1 to -5

Abstract

Salmonella spp. are zoonotic pathogenic agents that cause important infections in humans and animals. They are the most common foodborne pathogens after Campylobacter spp. worldwide. The aim of this study was to determine the phenotypic and genotypic extended-spectrum β-lactamase (ESBL) and colistin resistance of 67 Salmonella spp. isolated from retail chicken meats between May and December 2016, and stored in the culture collection of Ataturk University, Faculty of Veterinary Medicine, Department of Microbiology. The isolates were serotyped using multiplex polymerase chain reaction (mPCR). The serovar distribution of strains was 74.6% S. Infantis, 16.4% S. Enteritidis, 3.0% S. Arizonae, 3.0% S. Dublin, 1.5% S. Gallinarum and 1.5% S. Indica. Of the 67 strains, 20 (29.9%) were ESBL-positive. The main types of β-lactamase identified were blaCTX-M-1, blaCTX-M-8-25, blaSHV and blaTEM. Four isolates were found to be phenotypically colistin-resistant. These isolates did not carry mobilised colistin resistance (mcr) genes 1 to 5. In this study, both genotypically ESBL-producing and phenotypically colistin-resistant Salmonella strains were found. We revealed that ESBL-producing Salmonella strains have dramatically increased over the years, especially when compared with previously reported chicken meat Salmonella strains in Turkey. The increase in Salmonella strains, particularly ESBL producers and the colistin resistant, is of great concern for selected antimicrobial therapy in human infections. Hence, epidemiological information and monitoring systems are extremely important in controlling Salmonella infections in public health services.