الفهرس 
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Abstract
The aim of this study was to evaluate the microbiological quality of different types of curd dairy products and detection the possible sources of contamination,120 samples , 80 samples of cheese (20 samples each of Cheddar cheese, Ras , Feta and Processed cheese) and 40 samples of yogurt (20 plain yogurt and 20 stirred yogurt),were collected randomly from supermarkets, and street-vendors at Alexandria Governorate to determine the amount of total aerobic plate count (APC), Coliform, mold and yeast count with isolation of Escherichia coli( E. coli), Staphylococcus aureus and salmonella spp. and detection of AFM1.
The mean total aerobic plate counts in Feta, Ras and Processed cheese samples were 4.86 × 105 ± 0.13 × 105, 2.52 × 104 ± 0.68 × 104 and 7.96× 104±0.30×104 cfu/g, respectively.
There was high incidence of coliform in all examined samples as detected as 85%,90%,65% and 75% in Cheddar, Feta, Ras and Processed cheese samples, respectively. The mean total coliform counts were 4.04×103±1.36×103, 5.39×103±0.19×103, 1.21×103±0.36×103 and 1.64×103±0.40×103 cfu/g, respectively. they were 30% and 40% in plain and stirred yoghurt, respectively. The mean total Coliform counts were 3.50×102±1.25×102 and 7.25×102±1.57×102 cfu/g, respectively. All of them exceeded the permissible limit set by Egyptian Standard (2005), (˂10 cell ̸g), the most common Coliforms isolated from the examined cheese samples were Citrobacter freundii by 15, 35 ,10 and 20 %, respectively. The most common Coliforms isolated from the examined plain and stirred yoghurt were Enterobacter hafniae by 10% and 20% ,respectively.
While Escherichia coli were detected in Cheddar, Feta ,Ras, Processed cheeses samples as 25%, 35% ,10% and 20% ,respectively. While, in plain and stirred yoghurt as 5% and 5%, respectively. according to Egyptian Standard (2005) curd dairy products should be free from E.coli
Ten different serotypes were isolated from Cheddar, Feta, Ras and Processed cheese and from plain yoghurt ,four isolates belonged to serogroup O26:H11 (EHEC) (two isolates from Cheddar cheese , one isolates from Processed cheese and one isolate from plain yoghurt) .Two isolate belonged to serogroup O55:H7 (EPEC) (one isolate from Feta cheese and one isolates from Processed cheese). One isolate belonged to serogroup O86 (EPEC) (from Cheddar cheese). Two isolates belonged to serogroup O91:H21 (EHEC) (one isolate from Feta cheese and one isolates from Ras cheese). Three isolates belonged to serogroup O111:H2 (EHEC) (one isolate from Cheddar cheese, two isolates from Feta cheese). One isolate belonged to serogroup O114:H4 (EPEC) (from Processed cheese). Two isolates belonged to serogroup O124 (EIEC) (one isolate from Cheddar cheese and one isolate from stirred yoghurt). Three isolates belonged to serogroup O126:H21(ETEC) (two isolates from Feta cheese and one isolate from Processed cheese). One isolate belonged to serogroup O153:H2 (EPEC) from Ras cheese. The Enterohaemorrhagic E. coli (EHEC), was the most common isolated.
The incidence of staphylococci was 70%, 80%,50% and 70% in Cheddar, Feta, Ras and Processed cheese samples, respectively, and the mean total counts were 1.58×103±0.58×103, 1.54×103±0.53×103, 2.94 103±0.96×103, and 2.15×103±0.74 ×103 cfu/g, respectively. they were 30% and 35% in plain yoghurt and stirred yoghurt and the mean total counts were 6.33×102±1.58×102 and 1.10×103±0.55×102 cfu/g, respectively.
Staphylococcus aureus were detected in Cheddar, Feta, Ras and Processed cheeses ,plain and stirred yoghurt samples as 30%,55%,25%,35% ,15% and 20% ,respectively.
Salmonella were detected in 15 ,20 and 15 % of examined Cheddar, Feta and Processed cheese samples, respectively. There were 6 serovars isolated: S. enteritidis (10% ,5% in Feta and Cheddar cheese ,respectively), S. enteritidis was the most common serovar, followed by S. typhimurium (5%,5% in Feta cheese and Cheddar cheese), S. virchow (5%,5% in Cheddar and Processed cheese), S. tamale (5% in Feta cheese), S. tsevie (5% in Processed cheese) and S. papuana (5% in Processed cheese).
The incidence of yeast was 40%,35%,45% and 35% in Cheddar, Feta ,Ras cheese and Processed cheeses samples ,respectively, with the mean values 4.87×102±0.69×102, 4.57×102±1.26×102 ,9.44×102±3.91×102 ,9.85×102±5.17×102 cfu/g, respectively, and was 30% and 50% in plain and stirred yoghurt , respectively with the mean values 5.50×102±0.88×102 and 3.62 ×102±0.89×102 cfu/g ,respectively.
The present study indicated that 60%, 80,% 55% and 65 % of examined Cheddar, Feta, Ras and Processed cheeses samples were compatible with the Egyptian Standard .Furthermore,70% and 50 % of examined plain and stirred yoghurt samples were compatible with the Egyptian Standard .
Yeast isolated from examined Cheddar cheese samples were Candida albicans 10% , Candida parapsillosis 10%, Candida rugosa 10%, Rhoodotorula glutinis 5%, Rhoodotorula rubra 15%, Saccharomyces cerevisiae 10% and Torulopsis spp 25% .
While the distribution of yeast isolated from examined Feta cheese samples were Candida albicans 20% , Candida parapsillosis 10%, Candida rugosa 10%, Rhoodotorula glutinis 20%, Rhoodotorula rubra 5%, Saccharomyces cerevisiae 5% and Torulopsis spp 20%.
The distribution of yeast isolated from examined Ras cheese samples were Candida albicans 15% , Candida parapsillosis 15%, Rhoodotorula glutinis 10%, Rhoodotorula rubra 5%, Saccharomyces cerevisiae 5% and Torulopsis spp 35%. ,distribution of yeast isolated from examined Proceesed cheese samples were Candida albicans 10% , Candida rugosa 5%, Rhoodotorula glutinis 15%, Rhoodotorula rubra 20%, Saccharomyces cerevisiae 20% and Torulopsis spp 10%.
Distribution of yeast isolated from examined plain yoghurt samples were Candida albicans 10% , Candida parapsillosis 5%, Rhoodotorula rubra 10%, Saccharomyces cerevisiae 10% and Torulopsis spp 10%. And distribution of yeast isolated from examined stirred yoghurt samples were Candida albicans 10% , Candida rugosa 10%, Rhoodotorula glutinis 5%, Rhoodotorula rubra 10%, Saccharomyces cerevisiae 5% and Torulopsis spp 30%. Torulopsis spp. Are the most yeast spp. isolated from examined curd dairy products.
The incidence of mold was 60, 55, 70 and 60 % in Cheddar ,Feta, Ras and Processed cheeses samples ,respectively. The mean values 6.75×102±1.44×102 ,4.54×102±0.89×102 , 1.92×103±0.74×103 and 1.34×103±0.49×103 cfu/g ,respectively , and was 50 % and 65% in plain and stirred yoghurt, respectively with the mean values 6.90×102±1.90×102 ,1.37×103±0.49×103cfu/g ,respectively., 40, 45 and 30% of examined Cheddar, Feta and Ras cheese ,respectively were compatible with the Egyptian Standard, 35% of examined stirred yoghurt samples were compatible with the Egyptian standard .
The frequency distribution of molds isolated from examined Cheddar cheese samples were Aspergillus. Flavus 15% , Aspergillus fumigatus 10%, Aspergillus niger 10%, Cladosporium spp 5%,Fusarium spp 10% ,Nigrospora spp. 5% ,Penicillium spp 25% and Rhizopus spp 5%. While the frequency distribution of molds isolated from examined Feta cheese samples were Aspergillu flavus 10% , Aspergillus fumigatus 5%, Aspergillus niger 15% , Cladosporium spp. 15%, Fusarium spp. 5% Mucor spp. 5%, Penicillium spp 20% ,Thamnidium spp. 10% and trichoderma spp. 5%. .Distribution of molds isolated from examined Ras cheese samples were Aspergillus flavus 10% , Aspergillus fumigatus 10%, Aspergillus niger 15% , Cladosporium spp. 10%, Fusarium spp. 5% ,Mucor spp. 5%, Nigrospora spp 5%, Penicillium spp 45% , Rhizopus spp 10%., and Trichoderma spp. 5%. Distribution of molds isolated from examined Processed cheese samples were Aspergillus flavus 15% ,Aspergillus niger 5% , Cladosporium spp. 5%, Penicillium spp. 40% , ,Thamnidium spp. 5% and Trichoderma spp. 10%.
Concerning the distribution of molds isolated from examined plain yoghurt samples, they were Aspergillus flavus 5% , Aspergillus niger 5% , Cladosporium spp. 5%, Penicillium spp. 15% ,Rhizopus spp. 10% and ,Thamnidium spp 20% .While, the molds isolated from examined stirred yoghurt samples were founded to be Aspergillus flavus 15% ,Mucor spp. 10 % , Penicillium spp. 25% and Thamnidium spp. 5%. The obtained results showed that Penicillium spp. were the highest incidence mold in examined curd dairy products.
The Aflatoxin M1 was detected as 15, 5 ,15 and 10 % in Cheddar, Feta, Ras and Processed cheeses samples, respectively, with the mean values 0.671±0.239 ,0.429±0.0 , 0.850 ±0.324 and 0.401±0.273 ppb, respectively While the Aflatoxin M1 could not detected in yoghurt samples. According to the Egyptian Standards and EU regulation, all positive samples were above the permissible limit.
The significance and public health importance of such contaminants were discussed and suggestive control measures for producing clean and safe dairy products were discussed.