Incidence and virulence of Bacillus cereus isolated from Egyptian foods during four seasons

The incidence of Bacillus cereus in many food products including beef luncheon, koshary, karish cheese, double white cream cheese, white salty cheese and corn snacks was tested during four seasons. Generally, there was a high incidence rate during summer in all food samples and this rate decreased during winter. The incidence of B. cereus was high in karish cheese (25 to 80\%), koshary (45 to 70\%) and corn snacks (20 to 50\%) during the four seasons reflecting their ability to proliferate in milk products and starchy foods. All 38 isolates were motile and had the ability to ferment fructose and glucose, while 43 and 73\% were able to ferment lactose and salicin, respectively. Also, all isolates had the ability to utilize citrate, reduce nitrate into nitrite, grow at 7.5\% NaCl and hydrolyze casein but not urea. Meanwhile, the isolates showed variable results for anaerobic growth. In addition, all B. cereus isolates showed amylase, gelatinase and catalase activities and did not show any oxidase, cellulase or pectinase activities. Almost all the identified strains were pathogenic since they were able to produce several virulence factors. In addition, all isolates also were susceptible to ciprofloxacin, chloramphenicol and vancomysin antibiotics.