الفهرس 
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Abstract
A total of 250 random samples of some milk based foods were collected from different dairy shops, supermarkets, pharmacies, pastry shops and restaurants in Assiut city, Egypt. The samples were represented as pudding, rice pudding, custard, whipped cream and baby food that is powdered manufactured food designed for feeding to babies from 6 months (50 samples each). Each sample was obtained as sold to the public and dispatched directly to the laboratory with a minimum of delay. The samples were examined for B. cereus count as it is one of the most serious organisms responsible for milk deterioration and impairing the keeping quality of milk products causing food poisoning.
1- Incidence of Bacillus species counted using MPN technique on Bacara & MYP culture media:
B. cereus was detected in 43(86%), 45(90%), 47(94%), 50(100%) and 50(100%) of pudding, rice pudding, custard, whipped cream and powdered baby food, respectively.
2- Incidence of B. cereus in the examined samples cultured on both Bacara & MYP culture media:
On Bacara, B. cereus was detected in 15(30%), 22(44%), 13(26%), 21(42%) and 25(50%) while on MYP, they were 5(10%), 12(24%), 3(6%), 12(24%) and 13(26%) of pudding, rice pudding, custard, whipped cream and powdered baby food, respectively.
3- Frequency distribution of B. cereus in the examined samples grown on both Bacara and MYP culture media:
In pudding B. cereus was found on Bacara as 70, 10, 10, 2 and 8% while on MYP, it was 90, 2, 8, 0 and 0% lied in the range of ˂3, 3- ˂10, 10-˂102, 102- ˂103 and ˃103, respectively.
In rice pudding B. cereus was found on Bacara as 56, 14, 20, 6 and 4% while on MYP, it was 76, 0, 12, 12 and 0% lied in the range of ˂3, 3- ˂10, 10-˂102, 102- ˂103 and ˃103, respectively.
In custard B. cereus was found on Bacara as 74, 8, 18, 0 and 0% while on MYP, it was 94, 0, 6, 0 and 0% lied in the range of ˂3, 3- ˂10, 10-˂102, 102- ˂103 and ˃103, respectively.
In whipprd cream B. cereus was found on Bacara as 58, 0, 14, 8 and 20% while on MYP, it was 76, 0, 8, 8 and 8% lied in the range of ˂3, 3- ˂10, 10-˂102, 102- ˂103 and ˃103, respectively.
In powdered baby food B. cereus was found on Bacara as 50, 4, 46, 0 and 0% while on MYP, it was 74, 0, 26, 0 and 0% lied in the range of ˂3, 3- ˂10, 10-˂102, 102- ˂103 and ˃103, respectively.
The results were compared by the guidelines regarding the count of B. cereus growth on both Bacara and MYP culture media represented by (NSW, 2009).
4- Incidence of the isolated Bacillus spp. on both Bacara & MYP culture media:
On Bacara, B. coagulans was found as 2, 0, 2, 2 and 0%, B. licheniformis 0, 0, 0, 2 and 0%, B. megaterium 2, 0, 2, 4 and 0%, B. subtilis 0, 0, 0, 6 and 0%, while on MYP, B. coagulans was found as 4, 4, 0, 8 and 8%, B. licheniformis 8, 2, 10, 18 and 12%, B. megaterium 12, 2, 0, 12 and 12%, B. circulans 2, 2, 0, 2 and 4%, B. subtilis 8, 8, 14, 14 and 18%, B. sterothermophilus 2, 0, 4, 4 and 0%, B. macerans 0, 4, 0, 2 and 4%, B. sphaericus 0, 2, 6, 4 and 0% and B. polymyxa 0, 0, 0, 2 and 0% in pudding, rice pudding, custard, whipped cream and powdered baby food samples, respectively.
5- Detection of heamolysin BL (HBL) and cytotoxic K (CytK) genes from the isolated B. cereus strains using PCR:
Fifteen B. cereus isolates of the positive samples(3 random samples from each product) were investigated using multiplex PCR where 93.33% showed the presence of hblC and cytK virulence genes.
6- Studying the effect of storage temperature ( room temperature 29ºC and cooling 4ºC) on the growth of B. cereus in prepared rice pudding:
Rice pudding was chosen for its nutritional importance and wide spreading among the dairy shops and restaurants as a dessert with reasonable price and as it is a desirable food for infants.
The samples were inoculated with 2.4×104 cfu/g of B. cereus and it was found during 24h of investigations with 4h intervals that the count increased constantly reaching 1.5×106 cfu/g after 24h at 4ºC, while the sample was spoiled after 16h at 29ºC.
7- Studying the effect of added honey on the growth of B. cereus in prepared rice pudding:
The samples were inoculated with 2.4×104 cfu/g of B. cereus and it was found during 24h of investigations with 4h intervals that the count increased with a lower rate comparing with the samples with sugar.
Recommendations and suggestions were mentioned to prevent contamination of the milk based products evaluated in this study with B. cereus to avoid its spoilage and protect consumers from food poisoning and reduce risks on the public health.