Introduction to Foodborne Pathogens

Food microbiology can be divided into three focus areas; beneficial microorganisms, spoilage microorganisms, and disease causing microorganisms (Fig. 1.1). Beneficial microorganisms are those used in food fermentation to produce products such as cheese, fermented meat (pepperoni), fermented vegetables (pickles), fermented dairy products (yogurt), and ethnic fermented products such as sauerkraut, idli and kimchi. In fermented products (produced by natural or control fermentation), microorganisms metabolize complex substrates to produce enzymes, flavor compounds, acids, and antimicrobial agents to improve product shelf-life and to prevent pathogens growth and to provide product attributes. Microorganisms with their enzymes also breakdown indigestible compounds to make the product more palatable and easy to digest. In addition, the beneficial microorganisms also serve as probiotics to impart direct health benefit by modulating the immune system to provide protection against chronic metabolic diseases, bacterial infection, atherosclerosis, and allergic responses. Examples of beneficial microorganisms are Lactobacillus acidophilus, Lactobacillus rhamnosus, Lactococcus lactis, and Pediococccus acidilactici. Food spoilage microorganisms are those which upon growth in a food, produce undesirable flavor (odor), texture and appearance, and make food unsuitable for human consumption. Sometimes uncontrolled growth of many of the beneficial microorganisms can cause spoilage. Food spoilage is a serious issue in developing countries because of inadequate processing and refrigeration facilities. Examples of food spoilage microorganisms are Brocothrix, Lactobacillus, Bacillus, Pseudomonas spp., and some molds. The microenvironment created in a spoiled food generally discourages the growth of the pathogenic microorganisms, which are considered poor competitors.