Evaluation of Bacillus Cereus Contamination of Local Vegetables in Obosi, Nigeria.

Abstract

Seventy Nigerian local vegetables were examined for contamination by Bacillus cereus. The vegetables were purchased from different markets in Obosi, Anambra state, Nigeria and transported to the laboratory for microbiological analysis. The samples were first homogenized in 90ml of 0.1% peptone water and incubated at 37^oc for 24 hours. The clear supernatant were sub-cultured on to freshly prepared blood, MacConkey, PolymyxinB agar plates and incubated for 24hours at 37^oc. Bacillus cereus was identified using cultural characteristic, some biochemical tests, spore staining for the presence of lipid globules and polymerase chain reaction (PCR). Those positive were investigated for the presence of enterotoxin and their pathogenic effects using animal models was also done. Antibiotic sensitivity tests were carried out using agar diffusion methods. Thirteen (18.6%) of 70 vegetable samples were contaminated by Bacillus cereus. All Bacillus cereus were positive for enterotoxin and 100% resistant to ampiclox while one from cabbage was resistant to tested drugs. Histomorphological tests using animal models revealed infiltration of the liver cells by inflammatory cells, necrosis. This study showed that Bacillus cereus is a common contaminant of local vegetables in Obosi, Nigeria.

Keywords: Bacillus cereus, contamination, local vegetables, Obosi.