By conducting retrospective analysis, this study aim to investigate the resistance mechanism of quinolones in non-typhoidal Salmonella (NTS). A total of 105 strains of NTS isolated from clinical specimens from the Fifth Affiliated Hospital of Southern Medical University from May 2020 to February 2021 were used as research objects. VITEK2 Compact automatic identification drug sensitivity analysis system and serological test were used to identify the strains. The sensitivity of the strains to ciprofloxacin, levofloxacin and nalidixic acid was detected by AGAR dilution method. The whole genome of 105 strains of NTS was sequenced. Abricate and other softwares were used to analyze drug-resistant genes, including plasmid-mediated quinolone resistance gene (PMQR) and Quinolone resistance determination region (QRDR). Serotypes and ST types were analyzed using SISTR and MLST, and phylogenetic trees were constructed. The results showed that the NTS isolated in this region were mainly ST34 Salmonella typhimurium (53.3%). The drug sensitivity results showed that the drug resistance rates of NTS to ciprofloxacin, levofloxacin and nalidixic acid were 30.4%, 1.9% and 22.0%, respectively, and the intermediate rates of ciprofloxacin and levofloxacin were 27.6% and 54.2%.A total of 46 (74.2%) of the 62 quinolone non-susceptible strains carried the PMQR gene, mainly qnrS1 (80.4%), followed by aac(6')-Ib-cr(15.2%); there were 14 NTS and 8 NTS had gyrA and parC gene mutations, respectively. The gyrA was mutations at the amino acid position 87, Asp87Tyr, Asp87Asn, Asp87Gly, and Thr57Ser mutations were detected in parC. In conclusion, this study found that NTS had relatively high resistance to quinolones, carrying qnrS1 gene mainly resulted in decreased sensitivity of NTS to ciprofloxacin and levofloxacin, and gyrA:87 mutation mainly resulted in NTS resistance to Nalidixic acid; Salmonella typhimurium in clinical isolates showed clonal transmission and required further epidemiological surveillance.
通过回顾性研究分析，探究非伤寒沙门菌（NTS）对喹诺酮类药物的耐药性及耐药机制。以南方医科大学第五附属医院2020年5月至2021年2月临床标本中分离的105株NTS为研究对象，采用VITEK2 Compact全自动鉴定药敏分析系统和血清学实验对菌株进行鉴定；用琼脂稀释法检测菌株对环丙沙星、左氧氟沙星和萘啶酸的敏感性；对105株NTS 进行全基因组测序，采用Abricate等软件分析菌株的耐药相关基因，包括质粒介导的喹诺酮耐药基因（PMQR）和喹诺酮耐药决定区（QRDR）；采用SISTR和MLST分析血清型和ST型，并构建系统发育树。结果显示，分离的NTS主要为ST34鼠伤寒沙门菌（53.3%）。药敏结果显示NTS对环丙沙星、左氧氟沙星和萘啶酸的耐药率分别为30.4%、1.9%和22.0%，对环丙沙星、左氧氟沙星的中介率为27.6%、54.2%；62株喹诺酮类非敏感株中共有46株（74.2%）携带PMQR基因，主要为qnrS1（80.4%），其次为aac（6′）-Ib-cr（15.2%）；QRDR突变分析共有14株和8株NTS分别存在gyrA和parC基因突变，gyrA均为第87位氨基酸位点突变，分别为Asp87Tyr、Asp87Asn、Asp87Gly，parC检出Thr57Ser突变。综上，本研究发现，NTS对喹诺酮类药物耐药性相对较高，携带qnrS1基因主要导致NTS对环丙沙星和左氧氟沙星的敏感性下降，发生gyrA：87位点突变主要导致NTS对萘啶酸耐药；同时携带多种PMQR和存在QRDR突变，可导致NTS对3种喹诺酮类药物耐药。鼠伤寒沙门菌在临床分离株中存在克隆传播现象，需进一步加强流行病学的监测。.