Acid-fast bacilli (AFB) are a category of bacteria known to cause serious conditions like tuberculosis (TB) and other mycobacterial infections, including leprosy. If you are experiencing symptoms suggestive of active tuberculosis, your doctor might order AFB tests. Tuberculosis, a bacterial infection caused by Mycobacterium tuberculosis, primarily attacks the lungs but can also affect other vital organs such as the brain, spine, and kidneys. TB spreads through airborne droplets when an infected person coughs or sneezes.
TB can exist in two states: latent and active. In latent TB, the bacteria are present in your body but inactive; you won’t feel sick, nor can you transmit the infection. Active TB, however, is characterized by noticeable symptoms, and it is contagious.
Afb Diagnosis relies on detecting these bacteria in your sputum, a thick mucus expelled from your lungs when coughing – distinct from saliva or spit. Several AFB tests are available, each with a specific purpose in identifying and managing mycobacterial infections:
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AFB Smear: This is a preliminary test where a sputum sample is smeared onto a glass slide and examined under a microscope. While AFB smears can provide quick results, typically within 1 to 2 days, they are not definitive for diagnosing TB. A positive smear suggests a possible infection, warranting further investigation.
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AFB Culture: Considered the gold standard for AFB diagnosis, the AFB culture test involves sending your sputum sample to a laboratory to allow bacterial growth. This process can take 6 to 8 weeks as mycobacteria are slow-growing. A positive AFB culture definitively confirms TB or another mycobacterial infection, providing a conclusive diagnosis.
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Molecular Test (NAAT): This advanced test, often used in conjunction with AFB smear and culture, employs Nucleic Acid Amplification Testing (NAAT) directly on sputum samples. Molecular tests offer rapid detection of TB bacteria, often within just a couple of hours. Furthermore, these tests can identify if the TB bacteria are resistant to rifampicin, a commonly used antibiotic in TB treatment.
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Susceptibility Test: Typically ordered alongside an AFB culture, a susceptibility test determines the most effective antibiotics to combat the specific mycobacterial infection. Mycobacterium tuberculosis can develop resistance to certain TB medications, making this test crucial for guiding effective treatment strategies.
These AFB tests collectively play a vital role in the accurate diagnosis and management of tuberculosis and other mycobacterial diseases, ensuring timely and appropriate medical intervention.
