The presence of pathogens in food usually cannot be detected by sight or smell , nor can the presence of most chemicals and hard foreign objects. Food can make you very ill and yet may be the best-tasting food you have ever eaten. Your senses can be used to judge the quality of food, but can never be used to accurately judge the safety of food. The five classes of microbiological pathogens are as follows. Bacteria are single-cell microorganisms that are so small they can only be seen with a microscope.
Bacteria grow on and in soil, plants, animals and humans.
Human bacterial infections are often cured when antibiotics are administered. In the United States, these same antibiotics are sometimes used to stimulate growth and prevent disease in animals and poultry. As a result of the extensive use of antibiotics, some antibiotic-resistant strains of bacteria have developed. Because of this, often the best treatment for foodborne illness bacterial infections in humans may be bed rest and allowing each individual's immune system time to combat the source of infection. Viruses are not true living cells and are much smaller than bacteria.