广东省零售市场鸡肉中肯塔基沙门菌的流行情况及耐药性分析

本研究旨在了解广东省零售市场鸡肉中肯塔基沙门菌的流行情况、耐药水平与耐药基因携带情况。对2016年从广东省五个地级市采集的鸡肉样品进行沙门菌分离鉴定、血清型鉴定、药敏试验、耐药基因的检测和分子分型。结果显示,245份鸡肉样品中沙门菌阳性率为62.04%（152/245）,共鉴定出19种血清型,其中主要血清型有阿贡纳（Salmonella Agona,29/152,19.08%）、科瓦利斯（S.Corvallis,25/152,16.45%）以及肯塔基（S.Kentucky,20/152,13.16%）。肯塔基沙门菌药敏试验结果显示对磺胺异噁唑（100%）、萘啶酸（90%）、四环素（75%）、氨苄西林（65%）、头孢他啶（55%）、环丙沙星（55%）的耐药率较高,有85%（17/20）的菌株对3种及3种以上的抗菌药物耐药。对喹诺酮耐药基因的检测结果显示,95%（19/20）的菌株具有gyrA突变（Ser83Phe、Asp87Asn、Asp87Gly）,其中有57.89%（11/19）的菌株发生gyrA双突变（Ser83Phe与Asp87Asr、Ser83Phe与Asp87Gly）,5.26%（1/19）发生gyrA三突变（Ser83Phe、Asp87Asn、Asp87Gly）;100%（20/20）的菌株具有parC突变（Tyr62Ser、Ser85Ile）。45%（9/20）分离株携带质粒介导的喹诺酮抗性（PMQR）基因（aac（6'）-Ib-cr、qnrB、qnrS、oqxAB）,最常见的是aac（6'）-Ib-cr耐药基因。β-内酰胺类耐药基因bla_TEM-1、bla_OXA-1和bla_CTX-M-55的检出率分别为25%、10%和5%。PFGE图谱的聚类分析结果显示,肯塔基沙门菌之间具有不同的亲缘关系与遗传多样性,部分菌株具有高度同源性。肯塔基沙门菌在广东省零售市场鸡肉中是主要的流行血清型之一。其对传统药物磺胺异噁唑、萘啶酸、四环素和氨苄西林耐药较严重,对环丙沙星以及头孢他啶耐药尤其严重,具有多种多重耐药表型。肯塔基沙门菌其喹诺酮耐药决定区突变率高。分子分型揭示了菌株间跨地区传播的可能,为肯塔基沙门菌溯源提供一定的依据。

Analysis of Prevalence and Drug Resistance of Salmonella Kentucky in Chicken from Retail Markets in Guangdong

The aim of this study was to understand the prevalence, drug resistance and drug resistance genes carried by Salmonella Kentucky in the chickens from the retail markets in Guangdong province. The chicken samples collected from five prefecture-level cities of Guangdong in 2016 were selected to isolate Salmonella strains.Then the Salmonella serotypes were identified. Drug sensitivity test, drug resistance gene detection and molecular typing of the isolated S. Kentucky were carried out. As a result, 152 strains of Salmonella were isolated from 245 chicken samples, with the positive rate of 62.04% (152/245). Nineteen serotypes were identified, of which the main serotypes were S. Agona (29/152, 19.08%), S. Corvallis (25/152, 16.45%) and S. Kentucky (20/152, 13.16%). The drug sensitivity test of S. Kentucky showed that they were highly resistant to sulfafurazole (100%), nalidixic acid (90%), tetracycline (75%), ampicillin (65%), ceftazidime (55%), and ciprofloxacin (55%). Eighty-five percent (17/20) of the strains were resistant to three or more antimicrobial agents. The detection of quinolone resistance genes presented gyrA mutations (Ser83Phe, Asp87Asn and Asp87Gly) in 95% (19/20) of the strains, including double mutations in gyrA (Ser83Phe and Asp87Asr, Ser83Phe and Asp87Gly) in 57.89% (11/19) of the strains and triple mutation in gyrA in 5.26% (1/19) of the strains. In addition, parC mutations occurred in 100% (20/20) of the strains (Tyr62Ser and Ser85Ile). Forty-five percent of the isolates (9/20) carried plasmid-mediated quinolone resistance (PMQR) genes (aac(6')-Ib-cr, qnrB, qnrS, oqxAB), with aac(6')-Ib-cr resistance gene as the most common one. The detection rates of β-lactam resistance genes, encompassing bla_TEM-1, bla_OXA-1 and bla_CTX-M-55, were 25%, 10% and 5%, respectively. The results of cluster analysis of pulsed field gel electrophoresis (PFGE) map unveiled the genetic relationship between the serotypes of S. Kentucky, their genetic diversity, and high homology in some strains. It was found that S. Kentucky was one of the major epidemics in the retail chicken meat in Guangdong. It was more resistant to traditional drugs such as sulfisoxazole, nalidixic acid, tetracycline and ampicillin, and was particularly resistant to ciprofloxacin and ceftazidime, featuring multiple and multi-drug resistant phenotypes. S. Kentucky characterized high mutation rates in the quinolone resistance-determining regions of gyrA and parC. Molecular typing revealed the possibility of cross-regional transmission between strains, underpinning the studies on the traceability of S. Kentucky.