Chapter 16


Shared Mycobacterial Properties

• Mycobacteria are slow-growing, aerobic, facultative intracellular rods with a lipid-rich cell wall that makes them acid fast.

Cell wall components

Mycobacterial diseases (Table 16-1)

II Mycobacterium tuberculosis

Identification (Box 16-1)

1. Microscopic detection of acid-fast rods in sputum or biopsy specimen

2. Isolation by culturing on egg-based Löwenstein-Jensen medium or on special broth media

3. Serologic tests and DNA probes

4. Tuberculin skin test

• Intradermal injection of purified protein derivative (PPD) from cell wall induces a delayed-type hypersensitivity (DTH) response in those who have been previously exposed to M. tuberculosis or vaccinated.

• Positive reaction is indicated by an area of induration (>15 mm for healthy adults) 48 to 72 hours after PPD injection.

Transmission and incidence


1. Inhaled mycobacteria are engulfed by alveolar macrophages and replicate freely in these cells.

2. Sequence of formation of a tuberculous granuloma (type IV hypersensitivity reaction)

Jun 18, 2016 | Posted by in IMMUNOLOGY | Comments Off on Mycobacteria

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