Prevalence and genetic diversity of the strains of Bacillus cereus groups in food for infants and young children in Mxico

The aim of this study was to determine the prevalence and genetic diversity of the strains of Bacillus cereus groups isolated in México from foods for infants and young children. A total of 94 foods from a single commercial brand were analyzed to find B. cereus through a pre-enrichment method of colonial morphology in agar mannitol yolk polymyxin. Specific colonies were selected to be analyzed by polymerase chain reaction (PCR) determining the amplification of the 16S rRNA gene from B. cereus and the cytotoxin K gene. Eight strains were selected to determine genetic diversity (and relation) between the isolates from a PCR of repeated elements (rep-PCR), technique of molecular phylogeny that uses the primer (GTG) 5. The genetic similarity was determined by the Dice coefficient and from this a dendrogram was carried out. Isolates corresponding to strains from B. cereus group were detected in 9.2% (8/92) of the samples analyzed, 87.5% of the eight isolates showed the cytK gene. Groups of isolated strains were detected in meats and fruits and there was only one isolated strain from vegetables. The study shows the presence and propagation of strains from B. cereus group in foods for infants and young children commercialized in México. Key words: Bacillus cereus, México, genetic diversity, enterotoxin, infant food.