Resistance Profile of Salmonella spp. to Third Generation Cephalosporins and Quinolones in Chicken Carcasses from Rio de Janeiro, Brazil

Abstract

ABSTRACT Salmonella spp. is one of the major bacterial causes of foodborne gastroenteritis in humans. The aim of this study was to investigate antimicrobial susceptibility to cephalosporins and quinolones, and to identify the genetic mechanisms related to this resistance in strains of Salmonella spp. Seventy chicken carcass samples were collected from slaughterhouses in the state of Rio de Janeiro, Brazil. The phenotypic profile was detected by the disk-diffusion method and the search for genes encoding betalactamases, and resistance to quinolones was evaluated by PCR. The search for mutations in gyrA and parC was carried out by sequencing these genes. Eleven strains of Salmonella spp. of different serotypes were isolated. All the strains were resistant to at least one of the antimicrobials tested, and 63.64% (7/11) showed resistance to three or more antimicrobials. In the phenotypic test for ESBL production, 36.36% (4/11) of the strains were considered positive. PCR detected the resistance genes bla CMY-2, qnrB, bla CTX-M, and bla TEM. Among the isolates, 45.45% (5/11) simultaneously presented the bla CTX-M, bla TEM, qnrB genes and a mutation (Thr-57→Ser) in parC. Point mutations in the parC gene were detected in all the analyzed samples. Genes such as bla SHV, qnrA, qnrC, qnrD, qnrS, aac(6’)-Ib, qepA, and oqxAB were not detected. The study identified Salmonella spp. resistant to cephalosporins and quinolones, with resistance genes and mutations in parC, highlighting concerns about the adoption of biosecurity measures, responsible use of antimicrobials, and surveillance of resistant strains in the poultry chain.

Keywords

• Antimicrobial susceptibility
• cephalosporins
• chicken carcasses
• Salmonella spp
• quinolones