Genomic characterization of cephalosporin, quinolone and macrolide resistance in Salmonella enterica

Konyali, Diala
Salmonella infections are considered a significant burden in developing and developed countries. Each year, Non-Typhoidal Salmonella (NTS) causes more than 90 million cases of gastroenteritis, 85% of which are food-borne. Salmonellosis is usually self-limiting in healthy adults but might be severe in risk groups. Fluoroquinolones, macrolides, and cephalosporins are recommended when antimicrobial treatment is necessary. However, Salmonella is increasingly showing resistance to these antimicrobials by chromosomal mutations in DNA Gyrase and Topoisomerase, conferring plasmid-mediated quinolone resistance (PMQR) as well as having some of the extended-spectrum beta-lactamase genes, such as blaCTX and blaCMY. This study determined the resistance of 373 Salmonella isolates, isolated from food, animals, humans, and the environment between 2005 and 2020. Phenotypic examination of this resistance was carried out by disk diffusion method against ampicillin, ceftiofur, cefoxitin, ceftriaxone, cephalothin, ciprofloxacin, pefloxacin, nalidixic acid, trimethoprim-sulfamethoxazole, sulfisoxazole, azithromycin, and kanamycin. Then isolates that show resistance to any of the following antibiotics: ciprofloxacin, pefloxacin, ceftriaxone, and azithromycin were tested by PCR and gel electrophoresis for the presence of quinolone resistance genes and beta-lactamase genes as well as macrolide resistance gene. Isolates that conveyed resistance to fluoroquinolones were more than 32% (122/373). We observed an increased prevalence of mutated parC and gyrA genes accounting for the quinolone resistance. On the other hand, isolates that exhibited resistance to ceftriaxone were 2% accounting for 8/373. As for macrolides, 42% (106/250) showed resistance phenotypically, of which 10% harbored mphA gene. MDR isolates that possessed resistance genes were then further sequenced and characterized.


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Citation Formats
D. Konyali, “Genomic characterization of cephalosporin, quinolone and macrolide resistance in Salmonella enterica,” M.S. - Master of Science, Middle East Technical University, 2022.