21 other mycobacteria

7/26/2019 21 Other Mycobacteria

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MICROBIOLOGY LECTURE SERIES

LUZ GREGORIA LAZO-VELASCO, MD


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Mycobacterium avium Complex Mycobacterium kansasii

Mycobacterium scrofulaceum Mycobacterium marinum & Mycobacterium

ulcerans Mycobacterium fortuitum Complex Mycobacterium chelonae-abscessus


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Mycobacterium avium ComplexMAC; MAI (Mycobacterium avium intracellulare)

complex

infrequently cause disease in immunocompetenthumans

most common opportunistic infections of bacterialorigin in patients with AIDS

the risk of developing disseminated MAC infection inHIV-infected persons greatly increased with

CD4+ lymphocyte count


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Mycobacterium avium Complexincrease risk for disseminated MAC infection :

Pneumocystis jirovecii infection

severe anemiainterruption of antiretroviral therapypatients with cystic fibrosis and pulmonary

alveolar proteinosiscauses Lady Windermere syndrome- indolent

pulmonary MAC disease in middle-aged toelderly women in the absence of chronic lungdisease; nodules in middle lobe & lingual cavitation


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Mycobacterium avium ComplexOther manifestations:

Pericarditis

Soft tissue abscessesSkin lesionsLN involvementBone infectionsCNS lesions

Treatment : resistant to 1stline drugsClarithromycin or Azithromycin + EMBRifabutin, clofazimine, fluoroquinolones,

amikacin


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Mycobacterium kansasiiPhotochromogen

Produce pulmonary and systemic disease

indistinguishable from tuberculosisTx: RMP + EMB + INH

Mycobacterium scrofulaceumScotochromogenchronic cervical lymphadenitis in childrenTx: surgical excision of involved cervical lymph nodes

resistant to anti-TB drugs


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Mycobacterium marinum & MycobacteriumulceransOccur in water

Superficial skin lesions (Ulcers, swimming poolgranulomas)

Tx: surgical excision, tetracyclines, RMP, EMB Mycobacterium fortuitum Complex

Saprophytes found in soil & waterGrow rapidly in culture, form no pigmentSuperficial & systemic disease in humansTx: amikacin, doxycycline, cefoxitin, erythromycin,

RMP


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Described by Hansen in 1873 (9 years before Kochs

discovery of the tubercle bacilli) Not cultivated on nonliving bacteriologic media Causes leprosy

Typical acid-fast bacilli-singly, in parallel bundles or in

globular masses regularly found in scrapings from skin or mucous

membranes (particularly the nasal septum) inpatients with lepromatous leprosy


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bacilli often found within the endothelial cells ofblood vessels or in mononuclear cells

when bacilli from human leprosy (ground tissue nasal

scrapings) are inoculated in foot-pads of mice, localgranulomatous lesions develop with limitedmultiplication of bacilli


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Clinical findingsinsidious onsetlesions involve the cooler tissue of the body:

skin, superficial nerves, nose, pharynx, larynx, eyesand testiclesskin lesion: pale, anesthetic macular lesions 1-10 cm in

diameter; diffuse or discrete erythematous,

infiltrated nodules 1-5 cmin diameter; a diffuse skininfiltration


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Clinical findingsNeurologic disturbances:

nerve infiltration and thickening

anesthesia

neuritis

paresthesia

trophic ulcers

bone resorption

shortening of digits


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Feature TuberculoidLeprosy

LepromatousLeprosy

Type of lesion One or few lesions

with little tissuedestruction

Many lesions with

marked tissuedestruction

Number of acid-fastbacilli

Few Many

Likelihood oftransmitting leprosy Low High

Cell-mediated response Present Reduced orabsent

Lepromin ST Positive Negative


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Diagnosis

1. Scrapings with a scalpel blade from skin or

nasal mucosa or from a biopsy of earlobe skinare smeared on a slide and stained by the Ziehl-Neelsen technique.

2. Biopsy of skin or of a thickened nerve gives atypical histologic picture


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Treatment

1. Sulfones (dapsone) - first-line therapy for bothtuberculoid and lepromatous leprosy.

2. Rifampin or clofazimine included in initialtreatment regimens

3. minocycline4. clarithromycin5. some flouroquinolones


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Epidemiology transmission most likely to occur when small

children are exposed for prolonged periods to heavyshedders of bacilli Nasal secretions Incubation period: probably 2-10 years


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Prevention and Control

thorough examination of household contacts and closerelatives (complete skin & peripheral nervous system

examination)

The U.S Public Health Service National Hansens DiseaseProgram does not recommend routine dapsone prophylaxis

A therapeutic trial may be indicated for patients whose signsand symptoms are suggestive of leprosy but who do not havea definitive diagnosis.


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21 other mycobacteria

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