Abstract
Non-typhoidal salmonellosis remains a pressing public health problem worldwide. Quinolones, particularly fluoroquinolones, are widely used to treat various infections, including non-typhoidal salmonellosis, which can be a serious illness. The emergence of fluoroquinolone-resistant Salmonella has resulted in treatment failure and high mortality rates. In this study, we estimated the presence of plasmid-mediated quinolone resistance (PMQR) genes in Salmonella enterica isolated from human salmonellosis patients in South Korea from 2016 to 2019. We evaluated the association of these genes with fluoroquinolone susceptibility. Antimicrobial susceptibility tests for Salmonella isolates were performed using the Vitek II system, and the minimum inhibitory concentrations (MIC) of ciprofloxacin and levofloxacin were determined using the E-test method. Plasmid-mediated quinolone resistance (PMQR) genes were detected by PCR amplification and quinolone resistance-determining regions (QRDRs) of the gyrA and parC genes were analyzed following Sanger sequencing of the PCR products. Thirty-four Salmonella strains with reduced susceptibility to fluoroquinolones (ciprofloxacin MIC ≥ 0.125 µg/mL and levofloxacin MIC ≥ 0.25 µg/mL) were selected from 208 human clinical Salmonella isolates. Among them, 22 Salmonella strains harbored one PMQR gene (qnrA, qnrB, or qnrS), and three Salmonella strains carried two PMQR genes (qnrS and aac(6′)-Ib-cr or qnrA and qnrB). qnrS was the most common PMQR gene. Serotyping revealed that Salmonella 4,[5]12:i:- (32.4%, 11/34) and Salmonella Typhimurium (29.4%, 10/34) were the two most predominant serovars, and Multi-locus sequence typing (MLST) showed that ST19 and ST34 were the most frequent sequence types. In conclusion, qnr gene-positive Salmonella 4,[5],12:i:- and Salmonella Typhimurium were the main serovars responsible for reduced susceptibility to fluoroquinolones. Therefore, our findings suggest that PMQR-positive Salmonella strains, which can be isolated from various samples including human, food, and the environment, should be carefully monitored.
Highlights
Salmonellosis is a disease caused by Salmonella that usually produces acute onset of fever, abdominal pain, diarrhea, and vomiting
The presence of plasmid-mediated quinolone resistance (PMQR) genes in Salmonella strains with reduced susceptibility to fluoroquinolones indicates that continuous monitoring and clinical attention are required
Thirty-four Salmonella strains with reduced susceptibility to fluoroquinolones were identified from Gyeonggi-do, South Korea, from 2016 to 2019
Summary
Salmonellosis is a disease caused by Salmonella that usually produces acute onset of fever, abdominal pain, diarrhea, and vomiting. The presence of PMQR genes in Salmonella strains with reduced susceptibility to fluoroquinolones indicates that continuous monitoring and clinical attention are required. The United States National Antimicrobial Resistance Monitoring System (NARMS) has indicated the presence of PMQR genes among Salmonella and other enteric bacteria isolated from humans, retail meat, and food animals in the United States. NARMS recently reported an increase in the proportion of ciprofloxacin-non-susceptible strains lacking nalidixic acid resistance [12]. In Canada, a relatively high prevalence of PMQR genes has been reported in human isolates of non-typhoidal Salmonella with resistance and reduced susceptibility to fluoroquinolones [13]. We aim to estimate the presence of the plasmid-mediated quinolone resistance genes and their association with fluoroquinolone susceptibility in non-typhoidal Salmonella isolates from human clinical samples in South Korea from 2016 to 2019
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