Gram-negative staining bacteria, which are the target of the present study, have been reported to contaminate milk as a consequence of milking cows affected by mastitis and from poorly sanitized utensils used during milking, transportation and storage processes. Bacterial contamination could arise from the cow’s udder, barn, milk collection materials, various ingredients added to dairy products and dairy farm workers. īacterial agents may contaminate milk at various stages of procurement, processing and distribution. Therefore, milk is known to be an efficient vehicle for transmission of disease causing agents to humans. These rich nutritional contents and the production and processing procedures in commercial milk production render it susceptible to contamination by a host of pathogenic microbes that could cause diseases in humans. Milk is largely made up of water, within which a wide range of nutrients including vitamins, proteins, fats and carbohydrates are suspended. Further studies are recommended to identify additional critical control points, and to assess zoonotic risk factors to consumers. These results highlighted the need to maintain appropriate sanitary and hygienic measures at each critical point in order to safeguard consumers from foodborne pathogens. This study showed the presence of diverse pathogenic gram-negative staining bacterial species in raw milk that may be attributed to the sub-optimal sanitary conditions in the production and processing of milk in the Gondar town region. Of particular interest was that no gram-negative staining bacteria were isolated from pasteurized milk samples with varying shelf life. Overall, 54 different bacterial species were indentified, and Escherichia coli (29.6%), Pseudomonas aeruginosa (18.5%), and Klebsiella pneumoniae (16.7%), were the most commonly identified gram-negative staining bacterial pathogens. Among all critical control points considered, transportation containers at milk collection centers and at processing plants were found to be the most heavily contaminated with gram-negative staining bacterial species. The results of the current study showed that conditions for contamination of raw milk at different critical points were due to less hygienic practices in pre-milking udder preparation, sub-optimal hygiene of milk handlers, and poor sanitation practices associated with milking and storage equipments. Standard bacteriological cultivation and biochemical assays were used to isolate and identify bacterial pathogens in the milk samples. The hygienic procedures applied during milking, milk collection, transportation, pasteurization, and postpasteurization storage conditions at these specified critical control points were evaluated. Milk sampling points included smallholder’s milk producers, dairy co-operatives, a milk processing plant, and supermarkets. Milk samples were collected from critical control points, from production to consumption, that were hypothesized to be a source of potential contamination. This cross-sectional study of gram-negative staining bacterial contamination of milk meant for human consumption was carried out from October 2010 to May 2011 in Gondar town, Ethiopia. Milk is highly prone to contamination and can serve as an efficient vehicle for human transmission of foodborne pathogens, especially gram-negative bacteria, as these are widely distributed in the environment.
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