即食米面制品中蜡样芽胞杆菌分离鉴定及毒力基因研究

Isolation,Identification and Virulence Genes Investigation of Bacillus cereus from Ready-to-eat Products of Rice and Wheat

为探究即食米面制品中蜡样芽胞杆菌的污染状况及食源性蜡样芽胞杆菌中毒力基因的分布规律,以餐饮服务场所采集245份即食米面制品为蜡样芽胞杆菌的污染调查材料,通过国标法及持家基因分离鉴定得到49株蜡样芽胞杆菌阳性株,并对其进行13种毒力基因的PCR检测。结果表明:蜡样芽胞杆菌的平均检出率为10.61%(26/245),阳性检出样品主要为盒饭及米饭,其蜡样芽胞杆菌平均检出水平为3032 CFU/g,其中以盒饭的检出程度最高。49株分离菌株均检出两种或两种以上的毒力基因,非溶血性肠毒素基因nhe和entFM检出率最高,分别达到100%及91.84%,是分离菌株的主要毒力基因;溶血素基因hblA、hblC、hblD检出率分别为20.41%、38.78%和40.82%。同时携带nhe三个基因又携带hblA、hblC和hblD基因的强毒株有7株,占14.29%,且这7株菌均含有entFM基因。呕吐型毒力基因ces、cer、EM1仅2株检出,检出率为4.08%。本研究对即食米面制品中蜡样芽胞杆菌的监控、预警及爆发引起食物中毒后追踪其感染源和传播途径及构建基因指纹图谱库和分子溯源平台具有指导意义。

In order to investigate the contamination status and the distribution of virulence genes of Bacillus cereus from readyto-eat products of rice and wheat,245 samples of ready-to-eat products of rice and wheat from catering service were selected for the pollution survey of B.cereus.Distribution of 13 virulence genes in 49 isolated B.cereus strains which were isolated by GB method and identified with housekeeping genes,were detected by PCR.The results showed that the average isolation rate of B.cereus in ready-to-eat products of rice and wheat was 10.61%(26/245).The detected positive samples were mainly bento and rice.Average detected quantity of B.cereus was 3032 CFU/g in this positive samples,in which bento were found to have the highest level.Two or more virulence genes in 49 isolated B.cereus strains were detected among which non-hemolytic enterotoxin genes nhe and entFM were the major virulence genes with the highest isolation rate,reaching 100%and 91.48%,respectively.The isolation rate of hemolysin genes hblA,hblC,hblD were 20.41%,38.78%,40.82%.There were 7(14.29%)strains with high virulent that carried 3 nhe genes and hblA,hblC,hblD virulence genes.And entFM gene was detected in the 7 high virulent strains.Emetic virulence genes(ces,cer,EM1)were detected only in 2 strains,with the isolation rate of 4.08%.The results gave guidance meaning for monitoring,early warning,tracing the infection source and transmission route after food poisoning,and it also could contribute to constructing the genetic fingerprinting library and molecular traceability platform of Bacillus cereus from ready-to-eat products of rice and wheat.