Identification And Multiocus Sequence Typing Of The Emetic Bacillus Cereus In Infant Food

Bacillus cereus is a foodborne pathogenic bacteria widely exist in the natural environment. It is easy to cause food contamination. The food poisoning caused by Bc was divided into two categories, emetic and diarrhea, the majority is emetic type, causing vomiting, diarrhea, dizziness,fatigue and other symptoms.We purchase 101 infant food from the market, 155 Bacillus cereus strains were detected from the samples, then the emetic Bacillus cereus strain were identified through the method of PCR,biochemical characteristics and phenotype of etimic strains were studied as well. We screened the unique emetic isolates by RAPD and ilvD Sequence analysis for technology and multilocus sequence typing(MLST),then got to know the allele number and sequence type(ST) of these isolates. The characteristics of evolution and genetic traits were studied by analysis 1706 isolates from MLST Bacillus database,including 989 STs coming from more than 50 countries.The Bacillus cereus detection rate was 98% of the 101 sample, the detection rate is extremely high, only a few samples were not polluted.43 emetic isolates were identified,accounting for27.7% of the total Bc isolates. 11 strains of etimic isolates were screened by RAPD and ilv D sequence analysis.Nine strains were identified as common ST26, and a new type ST989 of two strains were identified by MLST. ST989 and ST26 only have one allele difference, all belong to the same group in eburst algorithm, all of the emetic isolates were devided into three groups, and the detection rate is higher in the Asian region than others, explaining that emetic Bacillus cereus still were conservative in evolution. Studying the evolution of the strain relationship and regional distribution, we can understand the characteristics and evolution laws of their evolution and predict the outbreak of diseases and food poisoning.