上海市鼠伤寒沙门菌流行特征及分子分型研究

Epidemiological characteristics and molecular typing of Salmonella typhimurium in Shanghai

[目的]研究上海市2006—2007年鼠伤寒沙门菌腹泻病例株的分子流行病学特征。[方法]追溯2002—2007年食品中分离的鼠伤寒沙门菌来源,比较鼠伤寒沙门菌食源株与腹泻株的抗生素耐药性;对全球沙门菌监测(GSS)病例和食品中分离的鼠伤寒沙门菌进行血清、耐药表型和脉冲凝胶电泳(PFGE)分子分型。[结果]经培养确认的鼠伤寒沙门菌腹泻病例数,在2006—2007年本市非伤寒沙门菌型病例构成中仅次于肠炎沙门菌,食品菌株多源于禽(64.4%)和畜肉制品(17.8%),其多重耐药菌株显著高于腹泻株(P<0.05)。PFGE将7株食品株和44株腹泻株分为23种带型,优势型为1型(8株)、2型(6株)、29型(4株)、49型(8株)和6型(4株),与食源菌株完全匹配的仅有49型、6型共7个病例(15.9%,7/44)。PFGE-1型腹泻株在2006和2007年分别为2例和6例,2型分别为4例和2例。[结论]上海市鼠伤寒沙门菌腹泻病例存在高度散发和分散爆发的流行特征,没有与本地食品菌株相匹配的优势克隆型分别是PFGE 2型和1型,与市售生鲜类肉食品污染株之间的遗传同源性低。推测传染源可能由输入性传染源对食品等媒介形成二次污染所致。建议加强流行病学调查,以揭示潜在的传染源和传播途径。

[ Objective] To study the molecular epidemiological characteristics of Salmonella typhimurium（S. typhimurium） in diarrhea patients in Shanghai from 2006 to 2007. [ Methods ] A retrospective analysis from 2006 to 2007 was done to explore the source of food - borne S. typhimurium and make comparison in its drug resistance to antibiotics between food - borne and diarrhea strains. Data of S. typhimurium survey of patients on Global - Salm - Surv （ GSS ） and food were analysed , including serotype, drug resistance and pulsed field gel electrophoresis （ PFGE ）. [ Results] The number of diarrhea cases of S. typhimurium comfirmed by culture method was only next to that of S. enteritidis in cases of nontyphoidal Salmonella infection in Shanghai between 2006 to 2007. Food - borne S. typhi- murium strains were mostly from poultry （ 64.4% ） and meat products （ 17.8% ）. The antibiotic resistance of food - borne S. typhimurium was higher than those from clinical isolateed （ P 〈 0.05 ）. Seven food strains and 44 diarrheal strains were divided into 23 PFGE subtypes. The dominating subtypes were typel （8 strains） , type2 （6 strains） , type29 （ 4 strains ）, type49 （ 8 strains ） and type6 （ 4 strains）. Only in 7 cases, the diarrhea strains subtypes matched with food subtypes （ 4 strains were subtype 49, the other 3 strains subtype 6,15.9% ,7/44. Strains of PFGE subtype 6,13.3%, 6/45 ） . Diarrhea strains PFGE subtype 1 were 2 cases and 6 cases in 2006 and 2007 respectively. Subtype 2 were 4 cases and 2 cases in 2006 and 2007 respectively. [ Conclusion] Diarrhea with S. typhimurlum has epidemiological characteristics of being highly sporadic and sporadic outbreak in Shanghai. The dominant clone types which do not match with strains from local food are PFGE subtype 2 and 1. The genetic homology are low between strains from con- taminant local fresh animal meat and strains from diarrhea patients. We guess the origin of infection may be secondary food contamination by non - local patients. We suggest that epidemiological investigation should be enhanced to expose the latent infectious origin and transmission route.