Another major source of bacteria is people and animals including pets. In essence, the micro-organisms are almost everywhere. These microorganisms do not increase in size but increase in numbers. Limited numbers in food are not enough to cause illness. Therefore, control lies not only in reducing contamination, but in preventing conditions that would allow micro-organisms to multiply.
Bacteria reproduce by dividing.
Raw foods brought into the kitchen sometimes bring pathogenic microorganisms with them. For example, raw meat and poultry often carry Clostridium perfringens , Staphylococcus aureus and Salmonella bacteria. Eggs, when laid, may harbor salmonellae. Fish, shellfish and marine crustaceans are sometimes contaminated with Vibrio parahaemolyticus . Raw vegetables and spices are often contaminated with C. perfringens and Bacillus cereus .