Incidence, Characterization and Pathological Features of Bacillus Cereus in Soil, Raw Cereals and Meat in Anambra State, Eastern Nigeria

This study was conducted to determine the level of contamination of Bacillus cereus in soil, raw cereal and meat in Anambra State Nigeria. Eighty (80) different types of extra human samples made up of 10 each from soil from animal houses, moist soil, soil from plant roots, and dry soil, 10 each from raw cereal- maize, beans, rice and raw meat. Raw cereal and meat were randomly purchased from local food vendors and markets and soil samples were collected from different locations. Eighty human diarrheal stool samples from patients attending clinics and fifty (50) control stool samples from human volunteers were also evaluated for the presence of Bacillus cereus. All samples were transported to the laboratory for microbiological analysis. The extra human samples were first homogenized in 0.1% peptone water, incubated at 37oc for 24 hours and then subcultured on to freshly prepared blood, MacConkey and polymyxinB agar plates while a direct stool culture on the above plates were also done. Bacillus cereus was identified using cultural characteristics, Gram staining reaction, spore staining for the presence of lipid globules and polymerase chain reaction (PCR). Enterotoxin production by Bacillus cereus and its effect on animal models was done. Antibiotic sensitivity tests were carried out. Bacillus cereus was isolated in 11(27.5%) of 40 soil samples, 5(16.6%) of 30 cereal crops and raw meat 4(40%). Soil from animal houses and raw meat had the highest contamination of 4(40%) each from 10 samples studied. There was no significant difference (p>0.05) in the Bacillus cereus isolated from soil, raw cereal and meat samples. Bacillus cereus was isolated in 15(18.8%) of 80 diarrheal stool and 4(8%) of 50 control stool samples which difference was not statistically significant. ALL Bacillus cereus isolated were positive for the enterotoxin and resistant to ampiclox. The results of this study reveal that Bacillus cereus is a common contaminant of soil, raw cereals and meat and is mainly of the diarrheal type. Keywords: Bacillus cereus, incidence, characterization, pathological feature