Distribution and toxin genes of Bacillus cereus spores isolated from vegetables

The objectives of this study were to evaluate the prevalence of Bacillus cereus spores in vegetables and to investigate the toxigenic characteristics of spore isolates. The detection rate of spores was 26.7% (12 out of 45 samples) which possess a higher risk of food poisoning than vegetative cell. The occurrence rate of toxin genes in spore isolates were 91.7, 100 and 100% for hblCDA, nheABC and entFM enterotoxin genes, respectively. The cry gene and insecticidal toxin gene was detected in 10 out of 12 (83.3%) spore isolates. The presence and absence of cry genes is the only differentiated characteristic between B. cereus and Bacillus thuringiensis. Most vegetables were contaminated with B. thuringiensis spores. HBL and NHE enterotoxin were detected in 11 out of 12 (91.3%) spore isolates. Emetic toxin was only detected in one spore isolates. The insecticidal toxin (δendotoxin) was detected in 10 out of 12 (83.3%) spore isolates. Although we investigated a small number of spore isolates, most of them were B. thuringiensis which produced the insecticidal toxin and enterotoxins. Thus, it is necessary to reduce the contamination levels of B. cereus and B. thuringiensis spores in vegetables for the prevention of food poisoning.