Humans and bacteria survive in similar environments on a daily basis. Many bacteria never directly contact people, many interact with humans in a beneficial way and some bacteria result in harmful infections. In many cases, a species of bacteria that normally lives on human skin or tissue with no resulting infection can become an infectious agent under the right circumstances.
Escherichia Coli O157:H7
E. coli is a gram-negative, rod-shaped cell that is ubiquitous in the environment. Escherichia coli normally resides in the healthy intestines of humans. It is a beneficial bacteria in digestion, due to its ability to aid in vitamin absorption. One strain of E. coli in particular, O157:H7, can cause serious problems in humans. The O157:H7 strain does not normally occur in humans and is a member of the enterohemorrhagic E. coli. According to the University of Kansas, this strain of E. coli produces a toxin that causes damage to intestinal cells, loss of water and salts, and bleeding. Symptoms of infection with E. coli O157:H7 include mild-to-severe diarrhea and a bloody stool.
Clostridium Botulinum
C. botulinum is a gram-positive, rod-shaped cell that prefers an environment that lacks oxygen. Botulism infection comes from a variety of environmental sources, such as food, water and soil. Unlike E. coli, Clostridium cells do not have any beneficial strains to humans. Clostridium botulinum vegetative cells are killed when heated at 176 degrees F for 10 minutes, explains the U.S. Food and Drug Administration. Clostridium vegetative cells can form spores that protect the deoxyribonucleic acid, or DNA, in the cell against potential damage. One food known to commonly harbor C. botulinum cells is honey. The honey provides an oxygen-free environment for the growth of the cells. Parents are often advised to avoid feeding honey to infants, as the presence of C. botulinum cells could cause serious infection in their underdeveloped immune systems.
Mycobacterium Tuberculosis
M. tuberculosis is a gram-positive, rod-shaped cell that requires oxygen to grow. The Centers for Disease Control and Prevention notes that tuberculosis infections target the lungs, but can infect any organ in the body. Tuberculosis cells can exist in the body in two forms: latent and active tuberculosis. In latent tuberculosis, cells are in the body but do not cause an active infection due to successful immune function. In this case, an infected person shows no symptoms and is not contagious. With active tuberculosis, an active infection is occurring in the infected individual. The individual with active tuberculosis feels symptoms such as pain in the chest, coughing with sputum or blood, weight loss, and fever. People with active tuberculosis are contagious to the people around them.
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