Exercise 29 Mycobacteria

The genus Mycobacterium contains many species, a number of which can cause human disease. A few are saprophytic organisms, found in soil and water, and also on human skin and mucous membranes. The two important pathogens in this group are Mycobacterium tuberculosis, the agent of tuberculosis, and Mycobacterium leprae, the cause of Hansen disease (leprosy). However, Mycobacterium kansasii and the Mycobacterium avium complex (see table 29.1) cause disease in persons with chronic lung disease and are being seen more frequently as opportunistic pathogens in patients with leukemia and acquired immunodeficiency syndrome (AIDS). Table 29.1 summarizes some of the mycobacteria that are human pathogens according to the type of disease that they may cause. Species of mycobacteria that are commensals and not normally associated with human disease are listed as well.

Laboratory diagnosis of tuberculosis and other mycobacterial infection is made by identifying the organisms in acid-fast smears and in cultures of clinical specimens from any area of the body where infection may be localized. In pulmonary disease, sputum specimens and gastric washings are appropriate, but if the disease is disseminated, the organisms may be found in a variety of areas. Urine, blood, spinal fluid, lymph nodes, or bone marrow may be of diagnostic value, especially in immunocompromised patients. Any specimen collected for identification of mycobacte-

Table 29.1 Mycobacteria in Infectious Disease

Disease

Species

Host(s)

Route of Entry

Tuberculosis

Mycobacterium tuberculosis M. bovis

Human

Cattle and human

Respiratory Alimentary (milk)

Pulmonary disease resembling tuberculosis (mycobacterioses)

M. avium* M. intracellulare* M. kansasii M. szulgai M. xenopi

Fowl and human

Human

Human

Human

Environmental contacts? (water and soil)

Lymphadenitis (usually cervical)

M. tuberculosis M. scrofulaceum M. avium complex

Human Human Fowl Human

Environmental contacts? (water and soil)

Skin ulcerations

M. ulcerans M. marinum

Human

Fish and human

Environmental contacts? Aquatic contacts

Soft tissue

M. fortuitum M. chelonae

Human Human

Environmental contacts?

Hansen disease (leprosy)

M. leprae

Human

Respiratory

Saprophytes: water, soil; human skin and mucosae

M. smegmatis M. phlei M. gordonae

* Mycobacterium avium and M. intracellular are so closely related that they are often identified as the Mycobacterium avium complex.

* Mycobacterium avium and M. intracellular are so closely related that they are often identified as the Mycobacterium avium complex.

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Bacterial Vaginosis Facts

Bacterial Vaginosis Facts

This fact sheet is designed to provide you with information on Bacterial Vaginosis. Bacterial vaginosis is an abnormal vaginal condition that is characterized by vaginal discharge and results from an overgrowth of atypical bacteria in the vagina.

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