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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