4株E.coli O157:H7毒力基因检测及其冷应激损伤  

Detection of Virulence Genes of Four Escherichia coli O157:H7 Strains and Cold Stress Injury in the Bacteria

作　　者：水新云 王虎虎[2] 高峰[2] 江芸[1] 

机构地区：[1]南京师范大学金陵女子学院食品科学系,江苏南京210097 [2]南京农业大学国家肉品质量安全控制工程技术研究中心,江苏南京210095

出　　处：《食品科学》2016年第4期176-180,共5页Food Science

基　　金：国家自然科学基金面上项目(31371861)

摘　　要：采用多重聚合酶链式反应对4株大肠埃希氏菌O157:H7(Escherichia coli O157:H7)进行毒力特性评价,研究3种常用选择性生长基质对E.coli O157:H7的精确定量对比,筛选出的适宜选择性培养基用于冷应激时菌体损伤的研究。结果显示,菌株CICC 21530的stx1、stx2、eae基因均为阳性,NCTC 12900和牛肉分离菌1的eae呈现阳性,牛肉分离菌2三种毒力基因均为阴性,表明4株菌的致病性不同;4株测试菌在改良山梨醇麦康凯琼脂(cefiximetellurite sorbitol macconkey agar,CT-SMAC)上计数均显著低于胰蛋白胨大豆琼脂(tryptose soya agar,TSA)上计数(P<0.05),而SMAC和改良伊红美蓝琼脂(modified eosin methylene blue agar,m EMB)上的计数与TSA相比无显著性差异,表明改良SMAC对正常菌体既有较强抑制作用,不适合用于E.coli O157:H7的精确计数,可以选用SMAC或m EMB;进一步以SMAC和m EMB作为选择性培养基研究菌体在4℃冷应激时的损伤情况,结果表明冷藏过程中SMAC、mEMB及TSA上的菌数均逐渐下降,第10天时4株菌均发生了一定程度的损伤或死亡。本方法可为食品安全中E.coli O157:H7的定量评估和风险控制提供科学依据。In this study,the virulence genes of four Escherichia coli O157：H7 strains were detected by multiplex polymerase chain reaction（PCR）. Then three selective media were compared for enumeration of E. coli O157：H7 and the injury of E. coli O157：H7 under cold stress was also investigated with the appropriate selective medium. The results showed that CICC 21530 strain was positive for all the three genes stx1,stx2 and eae,while NCTC 12900 and one beef isolate were eae-positive,and two other isolates were negative for all the three virulence genes,which indicated that the pathogenicity of four strains was different. The counts of all four strains on three selective media were lower than those on tryptose soya agar（TSA）（P〈0.05） but there was no significant difference between them except for cefixime-tellurite sorbitol macconkey agar（CT-SMAC）,which indicated that CT-SMAC was not suitable for counting E. coli O157：H7 due to the greater inhibition on normal bacteria,while SMAC or m EMB could be used. Then the injury of E. coli O157：H7 stored at 4 ℃（cold stress） was investigated with each of these two selective media. The results showed that the counts on SMAC,m EMB,or TSA were decreased during the whole storage and some bacteria were injured or killed on the 10^th day. In the current study,the selective media for accurate enumeration of four E. coli O157：H7 strains with different virulence genes were finalized,which would provide the scientific basis for quantitative assessment and risk control of E. coli O157：H7 in food safety evaluation.

关 键 词：大肠埃希氏菌O157:H7 毒力基因 半致死损伤 冷应激 选择性培养基 

分 类 号：TS201.3[轻工技术与工程—食品科学]