DISCUSSION
Milk contaminated with disease-causing bacteria does not smell or look any different from non-contaminated milk, and there is no obvious way for the consumer to know if the milk is contaminated (Julia, 2010). Pathogenic bacteria in milk has been a major factor for public health concern since the early days of the dairy industry. Many diseases are transmissible via milk products. Traditionally raw or unpasteurized milk has been a major vehicle for transmission of pathogens (Vasavada, 1988). The health of dairy herd, milking conditions are basic determinant of milk quality. Another source of contamination by microorganisms is unclean teats. The use of unclean milking and transport equipment contributed also to the poor hygienic quality (Bonfoh et al., 2003).
As seen from Table (1). The incidence of Staph aureus was isolated from 9 (9%) farm's milk and 14 (28%) in milk from dairy shops, These results were nearly similar to those reported by Abdel-Hameed et al. (2004) who isolated Staph aureus from raw milk samples in proportion of 14.38%. However, the current results were less than those recorded by Chye et al. (2004), Letiţia et al. (2011) and Ekici et al. (2004) they showed that Staph aureus was isolated from more than 60%, 70% and 75% of the raw milk samples and higher than those found by Abdel-Hameed (2006). Tondo et al. (2000) reported that 35.2% of food handlers were asymptomatic carriers of Staphylococcus aureus, and that 90.4% of raw milk samples. While Salmonella species were isolated fromfarm's milk only in percentage of 5% the results were higher than those recorded by De Reu et al. (2004) and Abd El-Atty and Meshref (2007) who couldn't detected Salmonella species in raw milk samples.
Listeria monocytogenes wereisolated fromfarm's milk only in percentage of 4%. The above mentioned results were higher than those reported by Jensen et al. (1996) who demonstrated Listeria monocytogenes in only 1.2% of milk samples. However, the results were less than those recorded by
(Rohrbach et al., 1992), Canada 1.9% (Fedio and Jackson, 1990) and Iran 1.6% (Moshtaghi and Mohammadpour, 2007). The disparate levels of contamination which have been reported from localized studies might have been due to variations in regions or to variations in sampling and detection techniques.
Food-borne disease outbreaks associated with Salmonella have been known for a long time and continue to be a problem in both developed and developing countries (Bean et al., 1990). Most outbreaks have implicated foods containing eggs or poultry products. Nevertheless, there have been several outbreaks of salmonellosis for which milk or milk products were responsible. Contamination of milk usually takes place by Salmonellae from external sources. Sources can be faeces, the farmer or his family, polluted water, dust etc. Healthy cows can also regularly excrete Salmonellae in their dung. Salmonellosis is caused by the ingestion of living bacteria of the Salmonella group. In contrast to staphylococcal food poisoning, the ingestion of viable cells is necessary for salmonellosis. The number of cells which have to be ingested to cause disease varies according to the type of strain, the type of food consumed and the consumer. Numbers varying from one cell of Salmonella typhi to several millions of, for example Salmonella derby or Salmonella anatum, are mentioned (D’Aoust, 1989). Infants as well as very young and aged people are especially sensitive and a smaller dose can result in disease. In the present study, Salmonellae were isolated from farm's milk in a percentage of 5%. None of the milk form dairy shops and ultra heated milk from markets contained Salmonella species. Salmonellae are sensitive to heat treatment and are readily destroyed at milk pasteurization temperatures. Pathogenic bacteria in milk has been a major factor for public health concern since the early days of the dairy industry. Many diseases are transmissible via milk products. The health of dairy herd, milking conditions are basic determinant of milk quality. Another source of contamination by microorganisms is
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De Reu et al. (2004) who could isolate Listeria monocytogenesin percentage of 6.3%. Poor hygiene often arises from poor handling at the farm, at collection centers, during transportation and at retail points. Common sources of bacterial contamination, especially coliforms, are faeces (of animal or human origin), personnel, water and containers. A high bacterial count reduces the shelf life of milk and enhances the risk of milk-borne bacterial infections and intoxications if the milk is not properly heated or if thermal injured pathogens recover under suitable temperatures (Kayihura et al., 1987).
Coagulase - positive Staphylococci species enterotoxin-producing staphylococcal species, Staphylococcus aureus in particular, are the leading cause of food-borne illness throughout the world. Sickness results from the ingestion of one or more preformed staphylococcal enterotoxins in staphylococcus contaminated food. The pathogenicity of Staphylococcus aureus has been recognized for many years, it may cause mastitis and/or skin diseases in milk-producing animals or lead to 36type of food-borne intoxications in consumers of milk and milk products (Bolstridge and Roth, 1985). Contamination with coagulase-positive Staphylococci was particularly high in raw milk from different farms and Markets (above 5x102 cfu/ml). The source of this contamination is difficult to trace due to the ubiquitous nature of staphylococci. Staph aureus is carried in the nose of some 30% of persons, who also tend to be skin carriers, and it is frequent in a number of animals (Olsvic et al., 1982). The enterotoxins of Staphylococci are remarkably resistant to heat. Baird-Parker (1990) states the temperature conditions for destruction of Staphylococcus aureus to be: 0.43 – 8 minutes at 60°C compared to 3 – 8 minutes at 121°C for enterotoxin.
In this study, the prevalence of Listeria. monocytogenes (4%) was found in farm's milk. Similar frequency findings of Listeria monocytogenes (0-5%) raw milk samples have been reported from different countries such as Austria 1.5% (Deutz et al., 1999), Spain 3.6% (Gaya et al., 1998), India 1.7% (Adesiyun et al., 1996), USA 4.1%
unclean teats. The use of unclean milking and transport equipment contributed also to the poor hygienic quality (Bonfoh et al., 2003). The machine-milking may increase the incidence of mammary infections either by a role as vectors of pathogens from infected areas to healthy neighborhoods, either by contamination of the teat force, its role is traumatic for the teat canal, while diminishing effect "barrier" (Boudry, 2005). As a result of the research, the samples of milk examined contained pathogenic microorganisms. This may indicate that analyzed milk can contribute a potential risk for public health in the cases that it is consumed or used in the production of dairy products such as cheese, butter, cream and ice cream without being pasteurized or being subjected to a sufficient heat process.
In this study the Ultra Heat Treatment milk (UHT) from markets was free from Staph aureus, Salmonella speciesand Listeria monocytogenes. This result agree with the (Egyptian standard, 2005) and (Riadh, 2005) who mentioned that the UHT milk should be free from pathogenic microorganisms.
Conclusion
The presence of Staph aureus, Salmonella speciesand Listeria monocytogenes in farm's milk and milk from dairy shops samples recorded in this study is expected as the produced milk is liable to contaminate from different sources (dust, air, water, equipments, milkers and handlers), moreover, the prevailing of bad handling, poor sanitation of equipments and lake of cooling facilities during transportation. Ultra Heat Treatment milk (UHT) from markets which are free from any pathogens indicated that Ultra Heat Treatment milk (UHT) is fit for human consumption because it gave a real indication for the good hygienic practice during production and handling.
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