RESUMO
Food are considered substances that contribute to maintain the functional equilibrium of living organisms. Many of these products are good substrates to support microbial growth. The normal state of human health will be negatively affected by foods highly contaminated with pathogenic microorganisms or their toxins. Diarrhea, fever and other symptoms may be produced by bacterial infections or bu some of their harmful toxins. Microbial foodborne illnesses are of importance in public health, specially in communities with defective nutrition and when a circle of infection-undernutrition-deficient inmunological response and again infection is established. Infections are diseases caused by pathogenic bacteria (Salmonella, Shigella and others), that entering the body through the mouth with the meals and may produce colonization or invasiveness at intestinal level, as well as tissue pertubations and diarrhea. Intoxications may be caused by preformed toxins in foods, being some of them thermolabile as that of Clostridium botulinum, or thermostable as those of Staphylococcus aureus. Some strains of Clostridium perfringes and Escherichia coli after passing the gastric barrier, are able to produced their respective toxins in the intestinal tract. The synthesis of bacterialtoxins may be coded by genes located in the chromosome or in extrachromosomal plasmids. By adjusting some physico-chemical parameters is posible to control microbial growth of the agents involved in food-borne illnesses. Among those related to intrinsic properties of good are: pH, water activity, potential redox, nutrients and biological structures. Others, depend on external conditions which may influence on their velocity of multiplication such: temperature, relative humidity and presence of gas. Also are of importance the interactions among mixed pipilations, that influence growth kinetics and determine the advantage of one specie over other...