الفهرس 
REVIEW OF LITERATUREOnly 14 pages are availabe for public view
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Abstract
Objectively, the study aims to throw some light on the recent health safety situation of some local white soft cheese varieties towards certain pathogenic species and identification them and some of their specific phages to practically assess the potential biocontrol of any pathogenic microbe that may be found in a certain market white soft cheese variety. Therefore, the study was divided into two main parts
PART I: DETECTION OF SOME PATHOGENIC MICROBES IN LOCAL WHITE SOFT CHEESES AND IDENTIFICTION THEIR AVAILABLE SPECIFIC PHAGES
In this part, a total of eighty different white soft cheese samples, 20 from each type namely, Baramilli, Domiati, Kariesh and Tallaga were randomly during the period of May - June 2014 from various markets located at Cairo. Samples were transported under aseptic conditions to the laboratory.
Moreover, five sewage water samples were obtained from Fac. of Agric., Ain Shams Univ.; and Shoubra EL-Kheima station of drinking and sewage water. Before sampling the external surfaces were scrubbed with alcohol, flaming and taps were flushed. The obtained samples were taken in sterile amber glass bottle of 250 ml capacity and directly transferred to the Virology Lab., Agric. Microbiol. Dept., Fac. of Agric., Ain Shams Univ. in refrigerated container and then maintained at 4-8 oC. The microbiological analysis was carried out within 12 h of sampling, including bacteriophage isolation.
The obtained results could be summarized as follow:
1. Realistically, Baramilli cheese possessed the highest infection level (70%) with pathogens followed by Domiati or Kariesh (50% for each), while Tallaga cheese contained the lowest level of contamination with pathogens (40%).
2. Minutely, 20% of infected Baramilli cheeses were contaminated with one pathogenic specie, 20% with two species and 30% with three or four pathogenic species (30% for each). On the other hand, 30% of positive Domiati cheese samples were infected with one pathogen specie, while the rest infected samples (20%) were found to be contaminated with two pathogenic species. Nevertheless all infected Kariesh cheese was observed to be contaminated with two pathogenic species. Moreover all infected Tallaga cheese was found to be contaminated with either one (20%) or two pathogenic strains (20%).
3. Specifically, most cheese infected with E.coli was found in Baramilli cheese (60% with a log count ranged from 1.49 to 2.60 CFU/g) followed by Kariesh cheese (50% with a log count fluctuated from 1.66 to 2.62 CFU/g), Tallaga cheese (30% with a log count fluctuated from 1.55 to 1.75 CFU/g) and Domiati cheese (20% with a log count ranged from 1.11 to 1.32 CFU/g). Likewise, most of staphylococci were detected in Baramili cheese (50% with a log count ranged from 2.65 to 3.71 CFU/g) followed by Domiati cheese (40% with a log count ranged from 1.59 to 2.80 CFU/g), Kariesh cheese or Tallaga cheese (20% for each of them with a log count fluctuated from 2.06 to 2.88 CFU/g for the former and 2.81 to 4.01 CFU/g for the latter). While, Salmonella sp. has been found to possess of 30% of infected Kariesh cheese followed by Baramili cheese (20%). Whilst, any of Domiati cheese or Tallaga cheese came in the last order (10% for each). Baramilli cheese was the sole cheese which was contaminated with Listeria monocytogenes in all surveyed white soft cheese ( SWSC) studied.
4. Identificationally, detected pathogen spices of SWSC using either biochemical methods or polymerase chain reaction (PCR) technique confirmed that, the detected E.coli was two strains namely E. coli O121and E. coli O104:H21, Salmonella sp. was defined to strain of S. typhimurium. Staphylococcus sp. was found to be Staph. aureus. Moreover the strain of L. monocytogenes was stated.
5. Virologically, electron microscopy of Salmonella bacteriophage particles revealed that, the virus is long, curled contractile tail. The phage particle has an isometric head with diameter of about 91.11 nm and the tail has 23.07 nm in length. The phage assigned to family Myoviridae as indicated by the presence of along contractile tail. The Salmonella phage had highly stability at different temperature ranged from -20 ºC to 42 ºC for 7 days. The phage was gradually harmed as the thermal temperature increased, so that, full phage damage was occurred at 80ºC or more. The viral infectivity was determined qualitatively by the spot test technique. The virus lost ability to lyses Salmonella cells at pH values of 9, 10, 11 or 12. It was active only at pH values of 4, 5, 6, 7or 8. Spot test showing the bacterial lysis caused by virulent bacteriophage specific for S.typhimurium.4
PART II: APPLICATION OF SALMONELLA BACTERIOPHAGE IN KARIESH CHEESE PRESERVATION
In this part, Kariesh cheese was made from pasteurized skimmed buffalo’s milk warmed at 40o C, inoculated with 2% of freshly activated bacterial yoghurt starter culture and then divided into 5 equal portions. The 1st portion was the control. The 2nd, 3rd, 4th and 5th portions were contaminated with equal levels (1%) S. typhimurium suspension containing 105 colony forming unit (CFU)/ml followed by adding phage suspension 108 plaque forming unit (PFU)/ml at the levels of nil, 1, 2 and 3% respectively. All portions were separately incubated at the same temperature up to curdling. The curds were cut and individually filled into stainless steel moulds lined with cheese cloth and consolidated by a slight pressure for 24 h. The blocks of curd were then cut, dry salted using 2% NaCl (w/w), packaged into plastic containers and at refrigerator 5±2°C for periodically analyses along 14 days.
The obtained results could be summarized as follow:
1. Physiochemically, the dry matter (DM), ash and salt contents of cheese varied significantly among either the contamination with S. typhimurium or the level of bacteriophage suspension spiked. The presence of S. typhimurium weakened the ability of cheese curd to drain whey while, the adequate control of pathogen with its bacteriophage has helped the curd to reject whey to be like the non-infected cheese curd (the control). While, the prolonging of cold storage period (CSP) to 14 days did not lead to any significant changes in both criteria of all cheese samples studied.
There was a significant increment in the protein /DM content associated with the ascending spiking level with bacteriophage suspension. While the CSP caused nonsignificant differences in the criterion.
The low fat content was slightly significant affected either by the level phage suspension added or the CSP of resultant product and did not exhibited any obvious trends.
Moreover, the acid development was significantly slowed due to the presence of phage suspension at any level. Nevertheless the differences in the TA% of cheese along the CSP were not significant.
Furthermore, the pH value of cheese did not exhibit any significant changes whether among the spiking level of the phage suspension or along the CSP for 14 days.
2. Bacteriologically, there were proportional reductions in lactic acid bacteria (LAB) population as the level of phage spiked into cheese milk increased, as which the reduction rate of LAB count during CSP prolonging was however declined.
3. In terms of health safety, although the number of pathogen microbe added was gradually reduced due to the acid developed by prolonging the CSP in the absence of phage, but it stilled present until the end of experimental period. While, the pathogen was completely eliminated within 7 days of cheese age when the phage suspension (108 PFU/ml) has been spiked at the level of 1% at least.
Finally, as a conclusion, the spiking of Kariesh cheese milk with 1% S.typhimurium phage suspension (108 PFU/ml) is quite enough to eliminate this microorganism when it present at a count as that gained when contaminated with 1% suspension containing 105 CFU S. typhimurium /ml. was added.
It is worthy to mention that, once this phage has been applied for the first batch, this technique should be considered as a continuous controlling system against this pathogenic bacteria. Whereas the discharged whey during cheese manufacturing will become as phage supply for the following batches.