Genetic Characterization Based on Four Housekeeping Genes of Sixteen Human-Pathogenic Bacillus Species Isolated from Foods, Cosmetics, and Environmental Surveillance Samples

Introduction: The genus Bacillus is a group of Gram positive, rod shaped, human pathogenic bacteria known to cause foodborne disease worldwide. This surveillance study was carried out to determine the presence of Bacillus spp. in foods, drugs, and cosmetics and, thereby, ensure that these commodities are safe and can be consumed by American people.

Purpose: The major objective of this study was rapid detection and differentiation of Bacillus spp. of public health importance by DNA sequencing of four housekeeping genes.

Methods: A total of 50 isolates belonging to 16 Bacillus spp. (Bacillus amyloliquefacians, Bacillus cereus, Bacillus circulans, Bacillus coagulans, Bacillus firmus, Bacillus laterosporus, Bacillus lentus, Bacillus licheniformis, Bacillus megaterium, Bacillus mycoides, Bacillus pumilus, Bacillus smithii, Bacillus sphaericus, Bacillus subtilis, Bacillus thuringiensis, and Bacillus vallismortis) were recovered from food, cosmetic, and environmental samples by enrichment followed by streaking onto selective media. Subsequently, sequence analysis was performed for all recovered isolates at the rRNA (ribosomal RNA), gyrB (DNA gyrase β subunit), rpoB (RNA polymerase β subunit) and tuf (TU elongation factor) loci using ABI 3500XL Genetic Analyzer.

Results: Species specific genetic polymorphism was observed for Bacillus spp. at the four housekeeping genes characterized. Nevertheless, the tuf, gyrB, and rpoB genes provided more resolution as compared to the 16S rRNA sequences. Thus, these three genes may be considered an efficient alternative target for identification and taxonomic analysis of Bacillus spp.

Significance: The results suggested that genetic discrimination for Bacillus spp. can be achieved by sequence characterization of the regions of rRNA, gyrB, rpoB, and tuf genes.