Phylogenic identification of toxigenic Bacillus cereus in chili and white pepper from Bogor area, Indonesia

Abstract

This study aimed to compare the occurrence and level of Bacillus cereus sensu stricto (B. cereus) in chili, and in previously isolated white pepper from traditional and supermarkets around Bogor, to determine the phylogenetic relationship between the obtained isolates based on their 16S rDNA gene, and to determine their potential toxicity based on ces and nheA genes using Polymerase Chain Reaction. The highest presumptive B. cereus level in samples from traditional and supermarkets was 5.95×105 and 2.6×105 CFU/g respectively. The difference in B. cereus levels between the two market types was not significant. Ten presumptive isolates from chili and 10 from white pepper from our previous study were sequenced, subjected to BLAST analysis, and 13 were confirmed as B. cereus sensu lato. The sequences were phylogenetically analysed and tested for the possession of nheA and ces toxigenic genes. Based on the phylogenetic tree established, 12 of 13 isolates were related to B. cereus, sharing >98% similarity with reference strains. All 12 (100%) isolates owned the nheA gene; none of them possessed the ces gene. Absence of ces gene lessens the danger for emesis from these spices, nonetheless, the 100% presence of nheA gene presents a potential risk for B. cereus diarrheal syndrome.