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Category: Bacterial Pathogenesis
Pathological Consequences of Commensalism, Page 1 of 2
< Previous page | Next page > /docserver/preview/fulltext/10.1128/9781555818104/9781555811594_Chap07-1.gif /docserver/preview/fulltext/10.1128/9781555818104/9781555811594_Chap07-2.gifAbstract:
This chapter discusses the classical distinguishing characteristics of persistent pathogens, that they elicit host responses, including inflammation, and that they have the capacity to damage the host, are increasingly being associated with the so-called commensal flora as well. The focus is mainly on the normal flora of the gastrointestinal tract. All external and certain, but not all, internal body surfaces are covered by a film of microorganisms, a normal microflora. The upper respiratory tract, gastrointestinal tract, perineum, vagina, and distal urethra contain large resident bacterial populations, while the bronchi, alveolar spaces, urinary tract, and uterus are normally sterile. Macrophages from animals colonized by a microflora also display increased cytotoxic activity, secrete more oxygen radicals, have increased levels of cyclic AMP, and produce more interleukin 1 (IL-1), IL-6, and tumor necrosis factor alpha in response to lipopolysaccharide (LPS) than macrophages from germfree animals. Intestinal immune responses are mainly induced in the Peyer's patches, which are mucosal lymphoid nodules covered by a specialized epithelium, the follicle-associated epithelium. Oral tolerance also protects us from exaggerated responsiveness, including inflammatory responses to antigens which are not dangerous, and thus minimizes the risk of inflammatory states in the mucosa. Colon cancer is one of the most common neoplastic diseases in wealthy populations but is relatively uncommon in developing countries. Staphylococci have been implicated in the pathogenesis of atopic dermatitis. Evidently, the epidemiological connection between the intestinal colonization pattern and allergy development needs to be further studied.
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Normal floras of the human body. The bacterial population densities of different external (bacteria per square centimeter) or internal (bacteria per gram o f contents) surfaces of the human body are indicated as follows: > 1010 bacteria, black; 108 to 1010, hatched; 105 to 108, lightly hatched; 103 to 105, dotted.
Normal floras of the human body. The bacterial population densities of different external (bacteria per square centimeter) or internal (bacteria per gram o f contents) surfaces of the human body are indicated as follows: > 1010 bacteria, black; 108 to 1010, hatched; 105 to 108, lightly hatched; 103 to 105, dotted.
Normal pattern of acquisition of the normal intestinal microflora by the newborn infant, a process which proceeds during the first years of life.
Normal pattern of acquisition of the normal intestinal microflora by the newborn infant, a process which proceeds during the first years of life.