Study of frequency of NHE complex genes in Bacillus cereus isolated from cow milk in Tabriz city

Bacillus cereus is a gram positive and spore producing bacterium that is widely spread in nature. Many of this bacterium strains cause food poisoning with signs of diarrhea and vomiting. Diarrhea-type diseases cause by haemolytic enterotoxins HBL, non haemolytic NHE and cytotoxin K. Milk is one of the food products that may be contaminated by livestock with mastitis caused by Bacillus cereus. The aim of this research was the study of frequency of NHE complex genes in Bacillus cereus isolated from cow milk in Tabriz city. 42 samples of Bacillus cereus isolated from cow milk after molecular confirmation were investigated for study of frequency of NHE complex genes by use of specific primers by PCR method. Of 42 tested samples, 41 positive cases were detected. Of 41 Bacillus cereus tested, 37 cases (90.2%), 35 cases (85.3%) and 31 cases (75.6%) harbored nheA, nheB and nheC genes, respectively. 30 samples (73.1%) simultaneously contained all three studied genes. In 3 samples (7.3%) of Bacillus cereus bacteria, no NHE complex genes were observed. The simultaneous presence of NHE complex genes in most of tested Bacillus cereus isolates indicates the high virulence of tested bacteria and their high pathogenic potential.