MLST analysis and distribution of virulence genes of Bacillus cereus from vegetables in Shanghai
To study the virulence gene distribution and the subtype of Bacillus cereus derived from vegetables in Shanghai,37 Bacillus cereus strains isolated from cucumber,lettuce,coriander,chicory,and sprouts were characterized.The results showed that 8 virulence genes(nheA,nheB,nheC,hblA,hblC,hblD,entFM,cytK)were detected in all the isolates except ces.The highest detection rate of virulence genes was nheB,followed by hblC,hblD,entFM,and hblA,with detection rates exceeded 80％.The detection rates of nheA and nheC were 78.4％and 64.9％,respectively,while cytK got the lowest rate(29.73％).According to the virulence gene carrying mode,37 isolated strains were divided into 14 types,among which type Ⅱ carried the highest rate.Type I,type Ⅱ,and type IV carried both Hbl and Nhe genes.In addition,MLST typing results showed that there were 30 STs and 5 CC groups in 37 isolated strains,ST4 and ST378 were the main STs.CC142 was distributed widely,it not only contained the most STs but also carried 5 virulence types.The distribution of virulence genes in STs was diverse.The above results indicated that Bacillus cereus in vegetables in Shanghai had potential enterotoxin hazards and presented genetic diversity,which had significant implications for monitoring,early warning,and tracking of the source of infection after outbreaks of food poisoning caused by Bacillus cereus.
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