[Modern diagnosis of tuberculosis]

Area of Science:

• Microbiology
• Infectious Diseases
• Medical Diagnostics

Background:

• Microscopic examination of sputum smears for acid-fast bacilli (AFB) is the quickest method for diagnosing contagious tuberculosis.
• Gene amplification techniques are currently unreliable for direct detection of Mycobacterium tuberculosis in AFB smear-negative clinical specimens.

Purpose of the Study:

• To review current diagnostic methods for tuberculosis, highlighting their speed and reliability.
• To discuss the role of culture, molecular methods, and immunologic tests in tuberculosis diagnosis and management.

Main Methods:

• Sputum smear microscopy for AFB detection.
• Bacterial culture on Lowenstein-Jensen or liquid media for identification and antibiotic susceptibility testing.
• Molecular methods (DNA probes, hybridization) for rapid identification of AFB and detection of resistance-conferring gene mutations (rpoB, katG).
• Interferon-gamma release assays (IGRAs) for diagnosing latent tuberculosis.

Main Results:

• Sputum smear microscopy is rapid but may miss smear-negative cases.
• Culture is essential but time-consuming (1-8 weeks).
• Molecular identification of AFB from culture is rapid (hours).
• Rapid detection of rifampin and isoniazid resistance mutations is possible within hours using molecular hybridization.
• Immunologic tests show promise for latent tuberculosis diagnosis.

Conclusions:

• Tuberculosis diagnosis integrates rapid microscopy, essential culture, and increasingly rapid molecular techniques.
• Molecular methods significantly shorten the time to identify Mycobacterium tuberculosis and detect key drug resistance mutations.
• Immunologic tests offer a valuable approach for diagnosing latent tuberculosis infection.