重庆市部分超市鸡肉中单增李斯特菌的耐药性与分子特征分析

Drug Resistance Analysis and Molecular Characterization of Listeria monocytogenes in the Chicken Meat from Some Supermarkets in Chongqing

为了解重庆市部分地区超市鸡肉中单增李斯特菌(Listeria monocytogenes,LM)的耐药性、毒力基因分布和分子特征,为LM监测程序的建立提供一定的数据支撑,以该地区5个超市鸡肉中分离鉴定的24株LM为研究对象,选用19种抗生素开展药敏试验;用PCR方法检测菌株携带的毒力基因,并开展血清型分型以及多位点序列分型(Multilocus sequence typing,MLST)研究.结果显示:24株分离株对苯唑西林(96.0%)、头孢噻肟(41.7%)和多粘菌素B(37.5%)的耐药率较高,多重耐药率为29.2%;24株单增李斯特菌中23株均检测出10个毒力基因,仅1株在inlB基因上出现基因缺失.血清型分型结果表明:24株单增李斯特菌大多为1/2型,另有4株致病性较强的4b型菌株.MLST分型共鉴定出11个序列型(Sequence type,ST),其中易引起单增李斯特菌病的常见ST型(ST87,ST9,ST2)菌株占50%(12/24),并发现1个新的ST型ST1011.该研究结果说明该地区超市鸡肉中单增李斯特菌的污染比较严重,耐药情况普遍,且分离株多是致病性较强的菌株.因此,加强对超市鸡肉中单增李斯特菌污染的监测和控制对有效降低潜在的风险具有重要的现实意义.

To understand the drug resistance,virulence gene distribution and molecular characteristics of Listeria monocytogenes(LM)in supermarket chickens in some areas of Chongqing and provide some data support for the establishment of LM monitoring program,a total of 24 strains of LM isolated from the chickens in 5 supermarkets in Chongqing were selected to analyze the drug resistances using 19 antibiotics.By using PCR,the virulence genes carried by those isolates were detected,and serotyping and multilocus sequence typing(MLST)were studied.The results showed that the 24 isolates had higher resistance rates to oxacillin(96.0%),cefotaxime(41.7%)and polymyxin B(37.5%),and multi-drug resistance rate of 29.2%.The isolates exhibited 100%sensitivity to cefalotin,ciprofloxacin,amikacin and nitrofurantoin.Virulence gene test showed that 23 of the 24 strains of LM had all virulence genes and 1 strain is a gene deletion of inlB gene.Serotyping indicated that most of the strains were 1/2a,1/2b and 1/2c,and there were 4 strains of 4b type strain with strong pathogenicity.A total 11 different STs were identified from 24 isolates by MLST.The 50%(12/24)of isolates were the common STs(ST87,ST9,ST2),which are susceptible to LM disease.A new ST,ST1011 was found.Phylogenetic tree analysis showed that the isolates with the same serotype were homogeneous.The results suggested that in supermarkets of Chongqing,contamination of LM in the chicken is considerably serious.In addition,the molecular characteristics analysis also demonstrated that most of the strains are potentially high pathogenic and commonly resistant to drug.It is of great practical significance to strengthen the monitoring and control contamination of LM in the chicken in supermarket for effectively reducing the potential risks.