ABSTRACT
While food is an indispensable source of nutrients for humans, it is also a source of microorganisms. Microorganisms in foods may be one of three types: beneficial, spoilage, or pathogenic. Beneficial microorganisms include those that produce new foods or food ingredients through fermentations (e.g., lactic acid bacteria and yeasts) and probiotics. The second type are those that cause spoilage of foods. Spoilage may be defined as an undesirable change in the flavor, odor, texture, or color of food caused by growth of microorganisms and ultimately the action of their enzymes. The final group are those microorganisms that cause disease. These microorganisms may grow in or be carried by foods. There are two types of pathogenic, or disease-causing, microorganisms: those causing intoxications and those causing infections. Intoxications are the result of a microorganism growing and producing toxin in a food. It is the toxin that causes the illness. Infections are illnesses that result from ingestion of a microorganism. Infectious microorganisms may cause illness by production of enterotoxins in the gastrointestinal tract or adhesion and/or invasion of the tissues. There are various types of pathogenic microorganisms that may be transmitted by foods including bacteria, viruses, protozoa, and helminths (Table 1). Certain molds (fungi) may also produce toxins (mycotoxins) in foods that are potentially toxic, carcinogenic, mutagenic, or teratogenic to humans and animals. Sources of these pathogenic microorganisms include soil, water, air, animals, plants, and humans.
