The term antimicrobial also encompasses drugs that kill protozoa. Antibiotics used in animals can make human diseases harder to treat by generating disease-causing organisms that will not respond to antibiotic therapy. One way stems from the fact that animals harbor strains of bacteria in their intestines that cause disease in people. Lacing an animal s food and water with antibiotics can lead to the build up of resistant organisms in the animal s intestines. Mechanized slaughter and processing often results in the contamination of animal carcasses with intestinal contents, including resistant bacteria.
People can become sick by, for example, eating undercooked meat with the resistant bacteria.
Although in most instances a foodborne illness resolves itself without treatment, serious cases require medical care including antibiotics. If antibiotics are required, but the disease-causing organisms are resistant, doctors may lack an effective drug to treat the illness. The organisms may be resistant because a number of the antibiotics used as growth promoters in food animals are the same as, or are related to, drugs used to fight bacterial disease in people. Drug-resistant traits can build up in organisms that are ordinarily harmless to both animals and humans, but which may become a problem under special circumstances. An example is with the group of bacteria called Enterococci , that are found in the intestines and usually do not cause problems.