Abstract
The present study was carried out to isolate Bacillus cereus group from 150 samples of cheeses marketed in Egypt. 33 isolates of B.cereus isolates were confirmed morphologically by colony characteristics and biochemically by using conventional biochemical methods. The potential of specific colonies of B. cereus were selected to possess ces-SYBR and HbLA gene. Results revealed that B. cereus group was isolated from 10/25(40%), 7/25(28%), 6/25(24%), 4/25(16%) 3/25(12%) and 3/25(12%) from examined Kareish, Damietta, Parmesan, Cheddar, Romy and Roquefort cheeses; respectively. B. cereus group was found in 33/150(22%) of the total analyzed cheeses, with mean ± SEM count of 1.06×104± 0.18×104 , 4.77×103 ± 0.65×103, 2.83×103± 0.49×103, 1.20×103±0.22×103, 8.00×102±1.37×102, 4.6×102 ± 0.61×102 (CFU/ g-1) for examined Kareish, Damietta, Parmesan, Cheddar, Romy and Roquefort cheeses; respectively. The potential of 33 selected isolates of B. cereus to produce protease and lipase was verified. From the tested isolates 19% and 11% were capable of producing, protease and lipase; respectively, indicating spoilage potentiality. The occurrence of emetic ces-SYBR gene of B. cereus strains was (+ve) in 12 (36.4%) and occurrence of diarrheal HbLA gene was (+ve) in 15(45.5%) for (+ve) B. cereus isolated from all tested cheeses. The obtained results indicate the possible risk of foodborne infections/intoxications that occur as a result of the possibility of the development of B. cereus in favorable conditions and consumption of cheese.

Key words: cheese contamination, B.cereus, HBLA gene; ces-SYBR gene