Investigation of the Presence of Extended Spectrum Beta Lactamase, Carbapenem and Colistin Resistances in Salmonella spp. Isolates by Phenotypic Method and PCR

The study was aimed to investigate extended-spectrum beta lactamase (ESBL) and carbapenem resistance by phenotypically and genotypically in Salmonella spp. strains isolated from stool samples of free-range chickens between August 2018 and January 2020. Also it was aimed to investigate colistin resistance gene mcr-1 by PCR. Stool samples collected from flocks’ ground from 110 different family-type chicken flocks by veterinarians about at least 25 grams of each flocks into the sterile containers for microbiological examinations in regions and villages of Balıkesir province. Salmonella spp. isolation were done according to ISO 6579-2017 method. A total of 34 Salmonella spp. isolates were identified based on biochemical characterization and confirmed by PCR targeting the 16S rRNA gene. ESBL and carbapenem resistance investigated by conventionally according to EUCAST methods. The presence of blaTEM, blaSHV, blaCTX-M, IMP, OXA-48 like, NDM, KPC resistance genes was investigated using the polymerase chain reaction (PCR) method. Colistin resistance was investigated by PCR method to determine the presence of mcr-1 gene. One isolate (2.94%) showing a meropenem inhibition zone <25 mm and resistance to piperacillin/tazobactam was classified as carbapenem-resistant. As a result of serotyping of carbapenem resistant isolate was identified as Salmonella Infantis. PCR analysis revealed the presence of both the IMP and OXA-48-like resistance genes in this strain. Phenotypic characterization supported the genotypic findings were resistance to temocillin indicated OXA-48-like carbapenemase activity, while the detection of a synergistic effect with dipicolinic acid (DPA) in the combined disk diffusion assay confirmed the functional expression of a metallo-β-lactamase (MBL) associated with the IMP gene. To the best of our knowledge, this study represents the first report of the detection of carbapenem resistance in Salmonella spp. isolates, isolated from chicken stool in Türkiye. The presence of carbapenem resistance was detected in one Salmonella isolate, serotyped as S. Infantis.