Characterization of extended spectrum β-lactamases in Colombian clinical isolates of non-typhoidal Salmonella enterica between 1997 and 2022

Introduction. Salmonella spp. is a zoonotic pathogen transmitted to humans through contaminated water or food. The presence of extended-spectrum β-lactamases is a growing public health problem because these enzymes are resistant to third and fourth generation cephalosporins. Objective. To characterize extended-spectrum β-lactamases in Salmonella spp. isolates received by the acute diarrheal disease/foodborne disease surveillance program of the Grupo de Microbiología of the Instituto Nacional de Salud. Materials and methods. A total of 444 Salmonella spp. isolates, resistant to at least one of the cephalosporins, were obtained between January 1997 and June 2022. The extendedspectrum β-lactamases phenotype was identified by the double disk test. DNA extraction was carried out by the boiling method, and the blaCTX-M, blaSHV, and blaTEM genes were amplified by PCR. Results. All the isolates were positive for the extended-spectrum β-lactamases test. The genes identified were: blaCTX-M + blaTEM (n=200), blaCTX-M (n=177), blaSHV (n=16), blaSHV + blaCTX-M (n=6), blaTEM (n=13) and blaSHV + blaCTX-M + blaTEM (n=3). Twenty-six isolates were negative for the evaluated genes. Positive extended-spectrum β-lactamases isolates were identified in Bogotá and 21 departments: Chocó, Magdalena, Meta, Bolívar, Casanare, Cesar, Córdoba, Quindío, Atlántico, Tolima, Cauca, Cundinamarca, Huila, Boyacá, Caldas, Norte de Santander, Risaralda, Antioquia, Nariño, Santander y Valle del Cauca. Conclusion. Resistance to third generation cephalosporins in Salmonella spp. isolates was mainly caused by blaCTX-M. Isolates were resistant to ampicillin, tetracycline, chloramphenicol, and trimethoprim-sulfamethoxazole (44 %; 197/444). The most frequent extended-spectrum β-lactamases-expressing serotypes were Salmonella Typhimurium and Salmonella Infantis.