This having been said members of the normal flora

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Unformatted text preview: been said, members of the normal flora themselves can cause disease under “abnormal” situations; for this reason they are called opportunistic pathogens Consider P. acne. Although this organism usually exists harmlessly on the skin, under conditions where there is excessive oil produced by the oil glands (an abnormal situation), it can cause acne. Acne commonly occurs during adolescence when the endocrine system is very active. Hormonal activity stimulates overproduction of “sebum”, the fluid secreted by the oil glands. Fermentation of the excessive oil secretions leads to hyper production fatty acids and these fermentation products irritate the skin producing inflammation (redness). In some individuals the inflammatory response is severe leading to swelling of the glandular ducts and plugging of the ducts by sebum, keratin and bacteria. These inflamed, plugged ducts result in inflammatory lesions commonly called blackheads or pimples. Since P. acne lives at the base of a hair follicle, it cannot be removed by topical treatments, washing with soap etc. Only drug treatments which inhibit oil secretion or antibiotics (P. acne is very sensitive to ) have an effect. The complex oily lipids secreted by oil glands in the moist areas of the skin can be fermented by certain skin bacteria producing volatile fatty acids with a strong odour. It is for this reason that many deodorants contain antibacterial additives to reduce body odour. Because it cannot penetrate the skin or mucous membranes, S. aureus is another Gram- FOOD-303 positive organism that usually exists harmlessly on the skin and in the nose. However, it can cause a variety of problems including skin infections, boils, pimples if permitted access the body through a prick in the skin, a cut or if large amounts of skin are disrupted (eg. by severe burns). In addition, if allowed to grow in large numbers in blood-soaked medical gauze packed into the nose after surgery, S. aureus can cause toxic shock syndrome (Similar conditions apply to toxic shock tampon use). The mouth The stomach Like the skin, Bacteria dominate the normal flora of the mouth in terms of both total biomass and diversity (current estimates are about 500 species). This is because there are many different microenvironments within the mouth. For example, the surface of the tooth provides an aerobic environment for bacteria that are able to stick (see below), whereas the gingival crevice provides an anaerobic environment, where bacteria can find a protected niche even when teeth are brushed regularly. In addition to bacteria, some protozoa are also present in the mouth as well as methanogenic Archaea in anaerobic gum pockets. Life in the mouth depends on being able to attach to surfaces. The flushing action of saliva and swallowing continuously remove bacteria from the mouth to the stomach as does desquamation of epithelial cells. Further, the surfaces of the mouth are highly colonized by microorganisms so finding an “empty space” to attach to is not easy....
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