Investigation of toxigenic Bacillus cereus isolated from raw and cooked rice in Sulaimani city, KRG.

Abstract

Bacillus cereus was isolated and investigated within 100 collected samples from raw and cooked rice in Sulaimani city. Twenty-nine out of these samples were found to be contaminated with this bacterium, the highest contamination rate occurred in raw samples 60% (24/40), followed by cooked rice 8.3% (5/60).  B.cereus densities in raw rice samples was 48.7 ×10⁴  CFU g−1, while in the cooked rice exceeded 10³ CFU g−1. Identification of the twenty-two strains of the B. cereus was done by VITEK 2 BCL, with probability between 85%-89% which is a good and acceptable level. Then identification of this bacteria at the molecular level was done by colony PCR using primers targeting 16S rRNA gene, diarrheal toxin including non-hemolytic enterotoxin (nheA, nheC and nheD), hemolytic enterotoxin (hblA, hblC, hblD), Cytotoxin K (cytK), bceT and entFM enterotoxin, in addition to the emetic toxin gene (detected by colony PCR). Out of the 22 positive samples, entFM gene was the more abundant (95.4%.) followed by cytK gene which was 77.2% and the percentage of   nheA, nheB, and nheC genes were 63.6, 13.6 and 40.9% respectively, and for hblA, hblC, hblD genes were 31.8, 22.7 and 31.8% respectively. The less percentage of these genes in these isolates was bceT (13.6). The detection of strains with the emetic toxin in raw and cooked rice was negative.