Pathogenic bacteria in milk have been a matter of public health concern since the early days of the dairy industry. Many diseases such as tuberculosis, brucellosis, diphtheria, scarlet fever, Q-fever, and gastroenteritis are transmissible via milk products.
Pathogenic bacteria are defined as those bacteria capable of causing disease, infection, or intoxication in a susceptible host. Staphylococcus aureus, Salmonella spp., Listeria monocytogenes, Escherichia coli O157:H7 and Campylobacter are the most frequent potential pathogens associated with milk or dairy products in industrialized countries and are the main microbiological hazards linked to raw milk and raw cheese.
Temperature has a key role in the spoilage of milk. If milk is produced in poor hygiene conditions then it contains increased numbers of psychrotrophic bacteria in the total microbial population and under low temperature contain proteinases and lipases of psychrotropic bacteria undergoes spoilage of milk product.
Generally, pathogenic microorganisms can contaminate raw milk in two ways.
*Endogenous contamination occurs when milk is contaminated by a direct transfer of pathogens from the blood (systemic infection) of an infected animal into the milk, or via an infection in the udder.
*Exogenous contamination, occurs where milk is contaminated during or after collection by animal feces, the exterior of the udder and teats, the skin, and other environmental sources.
Bacterial contamination in milk
