الفهرس 
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Abstract
One hundred and fifty samples of several cheese verities as kariesh, Domiati, Baramily, Processed cheddar, Romy and Roquefort (25 of each) representing different brands were collected from different retailers at Alexandria and El -Behara Governorates. Collected samples were kept in an ice box during transportation till reach to the laboratory with minimum time of delay under complete hygienic measures to be immediately examined microbiologically.
Total B. cereus count.
B. cereus was detected in 40%, 28%, 24%, 18%, 12% and 12% of Kariesh, Domiati, Baramily, Processed cheddar, Romy and Roquefort cheese samples receptively, with the total percentage of 33% in all examined samples. In Kariesh, Domiati, Baramily, Processed cheddar, Romy and Roquefort the minimum B. cereus count were 6×102, 3×102, 2×102, 1×102, 1×102 and 1×102. with the maximum B.cereus count were 3.9×104 , 1.1×104 , 8.5×103 , 2.7 ×103 , 1.5×103 and 9×102 with a mean value 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 ± 1.37×103 and 4.06×102 ± 0.61×102 cfu/g., respectively . B. cereus was detected in 22% with the minimum , maximum and mean value of 1×102 , 3.9×104 and 3.45×103±0.58×103 cfu/g. in total examined cheese samples, while the mean log of B. cereus in Kariesh , Domiati, Baramily, Processed cheddar, Romy and Roquefort were 4, 3.7 , 3.5 , 3 , 2.9 and 2.7 ( log cfu/g.) ; respectively.
The highest frequency distribution of B. cereus count cfu/g. lies within the range of 102 - 104 in 24%, 24% , 16% , 12% and 12% of Domiati, Baramily, Processed cheddar, Romy and Roquefort samples respectively ; While it lies within the range of 103 – 105 in 32% of Kariesh cheese samples. from the previous data Kariesh cheese samples were the highest contaminated kind of cheese with B. cereus microorganism due to unhygienic measures and low sanitation during handling and manufacture.
Proteolytic and lipolytic activities of isolated B. cereus organisms.
The proteolytic activity of isolated B.cereus ( 33strains) were 90%; 86%; 100%; 75%; 100% and 67% of examined Kariesh, Domiati, Baramily, Processed cheddar, Romy and Roquefort cheese samples, respectively; with a total percentage of 88% in all examined cheese samples.
Also the lipolytic activity of isolated B.cereus ( 33strains) were 50%; 57%; 50%; 75%, 33% and 0% of examined Kariesh, Domiati, Baramily, Processed cheddar, Romy and Roquefort cheese samples, respectively; with a total percentage of 48% in all examined cheese samples.
Antibiotic sensitivity of isolated B. cereus organisms.
The antimicrobial susceptibility of B. cereus isolated from the examined cheese samples and according to antibiotic discs (14 different antibiotic discs) susceptibility found that B. cereus isolated from examined cheese samples were highly susceptible to Amikacin 97%; Gentamicin (G) 87.9% and Tetracyeline 81.8% and susceptible to Ciprofloxacin (CP) 72.7% and Ampicillin (AM) 60.6% ; but show Intermediate susceptible to Cephalothin (CN) and Erythromycin (E) and highly resistance to Neomycin (N)100%; Kanamycin (K) 100%; Nalidixic acid (NA) 87.9% and Sulphamethoxazole (SXT) 84.8% and resistant also to pencillin G (P) 78.8%; Oxacillin (OX) 63.6% and finally to Cefotoxim (CF) 54.5%.
Detection of emetic and diarrheal toxins B. cereus organisms with high technique method (PCR).
Analysis of PCR products obtained from amplification reaction of extracted DNA indicates that ces- SYBR” was detected in 12 out of 33 isolates (36.4%). The ces- SYBR (emetic gene) was detected in positive B. cereus cheese samples (n = 33 strains) with the incidence of 50%; 28.6%; 33.3%; 50%; 33.3% and 0% in kariesh; Domiati; Baramily; Processed cheddar; Romy and Roquefort respectively with the total percentage of 36.4% in all examined cheese samples. And also by agarose gel electrophoresis revealed that HBLA (diarrheal gene) was detected in B. cereus cheese samples (n = 33 strains) with the incidence of 40%; 57.1%. 50%; 50%; 33.3% and 33.3% in kariesh; Domiati; Baramily; Processed cheddar; Romy and Roquefort respectively with the total percentage of 45.5% in all examined cheese samples.