南方食品中沙门氏菌污染调查及分型

Prevalence and characterization of Salmonella spp. from foods in South China

【目的】系统调查我国南方代表性地区食品中沙门氏菌污染情况,并对分离株进行血清分型和肠杆菌基因间重复共有序列聚合酶链式反应(Enterobacterial Repetitive Intergenic Consensus Polymerase Chain Reaction,ERIC-PCR)分型研究,为溯源和控制食品中沙门氏菌的污染提供数据。【方法】采用定性法和最大可能数(Most Probable Number,MPN)法对七大类食品(肉与肉制品、水产品、速冻食品、熟食、蔬菜、乳制品和食用菌)中的沙门氏菌进行检测。利用血清分型和分子分型确定南方沙门氏菌血清型的分布和优势血清型,研究分离株的遗传多样性。【结果】从400份食品样品共检出75份沙门氏菌阳性样品,污染率为18.8%(75/400)。其中,97.3%(73/75)的阳性样品污染水平均低于10 MPN/g。对93株分离株进行血清分型,分属9个群、29种血清型。优势血清型为德尔卑沙门氏菌(Salmonella Derby)和鼠伤寒沙门氏菌(Salmonella Typhimurium)。利用ERIC-PCR对96株沙门氏菌(包括93株分离株和3株标准株)进行分型研究发现,在相似系数为0.75时可分为15个聚类簇,56种型别,分离株的基因型别呈现多样性。【结论】南方食品中沙门氏菌的污染率较高,但污染水平低。S.Derby和S.Typhimurium为优势血清型。初步建立了沙门氏菌ERIC-PCR指纹图谱数据库,南方食品中沙门氏菌的血清型和基因型呈现多样性。

[Objective]In this study,we studied systematically the prevalence of Salmonella in foods from various parts of South China. Isolated strains were characterized by serotyping and enterobacterial repetitive intergenic consensus polymerase chain reaction （ERIC-PCR）,to provide data support for effectively tracing the source of Salmonella and controlling food contamination.[Methods]In total 400 unique food samples were collected from retail markets in South China,including meat product （74）,frozen product （56）,seafood （80）,mushroom （54）,ready-to-eat food （80）,vegetables （32）,dairy （24）.Food samples were examined by qualitative method according to national food safety standard （GB4789.4-2010） and most probable number （MPN） method. The predominant serotype of Salmonella was figured out when all isolated strains were characterized by serotyping using slide agglutination method. We also applied ERIC-PCR for genetic diversity analysis of Salmonella isolates.[Results]Of the total 400 food samples,75（18.8%） tested positive for Salmonella.The results showed that MPN value of 97.3% （73/75） positive samples below 10 MPN/g.Ninety-three Salmonella isolates were belonged to 9 groups and 29 different serovars. Salmonella Derby and Salmonella Typhimurium were the two predominant serovars. The isolated strains were further discriminated by ERIC-PCR.The results revealed 96 strains including 93 isolates,Salmonella Enteritidis CMCC 50335,Salmonella Typhi CMCC 50098 and S. Typhimurium ATCC 14028 were divided into 15 clustering groups and generated 56 genotypes according to the similarity coefficient of 0.75,which suggested various genotypes of Salmonella.[Conclusion]The overall prevalence of Salmonella was high,however lower contamination level in foods from cities of South China.S. derby and S. typhimurium were found to be predominant serovars.ERIC-PCR fingerprints database of Salmonella from food samples in South China were preliminarily established.Salmonella present in foods were phenotypically and genotypically diverse.