Bacterial Mouth Infections

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The oral cavity contains some of the most varied and vast flora in the entire human body and is the main entrance for 2 systems vital to human function and physiology, the gastrointestinal and respiratory systems. Several diseases involve these 2 systems and manifest in the oral cavity. In addition, a specific pathologic condition, such as periodontitis (ie, inflammation of the periodontal attachment of the teeth and the alveolar bone), may be present in the oral cavity. These specific conditions in the oral cavity may create foci of infection that can affect many other vital systems, such as the cardiovascular and renal systems. Foci of infection in the oral cavity arising from chronic periodontitis or chronic periapical abscesses (ie, inflammation and abscess of the tissue attached to the apex of the root) may lead to subacute bacterial endocarditis (BE) and glomerulonephritis (GN).

In addition to bacterial organisms, oral microorganisms can include fungal, protozoal, and viral species. The bacteria include hundreds of types of organisms of which only "22 predominant ones have been identified."[1] A variety of organisms in the microenvironment of the oral cavity adhere to the teeth, the gingival sulcus, the tongue, and the buccal mucosa. Each site has a unique way of allowing the organisms to establish their residency. The normal flora in healthy individuals maintains similar patterns. When a local or systemic disease process or concomitant use of medications alters this overall pattern, atypical organisms begin to predominate and some normal organisms with a benign nature, such asCandida albicans, become pathogenic.

The microenvironment of the oral cavity changes with the age of the patient, the eruption or loss of teeth, and the appearance of disease states (eg, caries, periodontal disease). Systemic changes, such as pregnancy or drug intake, also alter the number and proportion of flora. These changes are due to alterations in the flow and composition of salivary fluid and in the levels and activity of defense components (eg, immunoglobulins, cytokines) in the saliva.

Increasing evidence indicates that oral microbiota participate in various systemic diseases. Periodontal disease permits organisms to enter deep systemic tissues, such as the carotid atheroma. An association between periodontal pathogens, such as Porphyromonas gingivalis, and atherosclerosis has been suggested because of the pathogen's possible direct effect on atheroma formation. P gingivalis has also been found in carotid and coronary atheromas. It may also invade and proliferate within heart and coronary artery endothelial cells, and, along with Streptococcus sanguis, it may also induce platelet aggregation associated with thrombus formation. Oral microorganisms may also enter the deeper tissue after trauma or surgery, which contributes to the disease process, particularly when they cause BE.

Periodontitis is a common chronic bacterial infection of the supporting structures of the teeth. The host response to this infection is an important factor in determining the extent and severity of the disease. Systemic conditions may modify the extent of periodontitis principally through their effects on normal immune and inflammatory mechanisms.

Several systemic diseases, such as diabetes mellitus, may increase the prevalence, incidence, or severity of gingivitis and periodontitis. Medications such as phenytoin, nifedipine, and cyclosporin are known to predispose to gingival overgrowth and to increase the severity of plaque formation. Immunosuppressive drug therapy and any disease (eg, HIV infection) resulting in suppression of the normal inflammatory and immune mechanisms can cause or enhance severe periodontal diseases. Smoking, which has an adverse effect on periodontal health, also affects this overall disease condition. Specific diseases, such as histiocytosis, may result in necrotizing ulcerative periodontitis.

The severity and prevalence of periodontitis are increased in persons with diabetes and are worse in persons with poorly controlled diabetes. Periodontitis may exacerbate diabetes by decreasing glycemic control. This effect indicates a degree of synergism and a link between the 2 diseases.

The relative risk of cardiovascular disease is doubled in persons with periodontal disease. Periodontal and cardiovascular disease share many common risk and socioeconomic factors, particularly smoking, which is a powerful risk factor for both diseases. The actual underlying etiology of both diseases is complex, as are the potential mechanisms whereby the diseases may be causally linked. The chronic inflammatory state and microbial burden in persons with periodontal disease may predispose to cardiovascular disease in ways proposed for other infections, such as with Chlamydia pneumoniae.