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AFB Smear and Culture
Also known as: TB culture and sensitivity Formal name: Acid-fast bacillus smear, culture, and sensitivity Related tests: TB Skin Test
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Common Questions
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1. Can I be infected with TB and not be sick?
2. What is the difference between MDR TB and XDR TB?
3. Why is the doctor asking me to take my TB medication in the presence of a nurse?
1. Can I be infected with TB and not be sick?
Yes. There are about 10 to 15 million people in the United States, and many more worldwide, who have a latent form of TB infection. They have been exposed to the bacteria but their body's immune system has confined it to a few of their cells, in an inactive form. People with latent TB infections are not sick and they are not infectious, but the bacteria are still there and still alive. If those with latent infections are tested, most would have a positive TB skin test. The majority of people with latent TB infection, about 90%, will never progress to active tuberculosis disease.
Those who do have active TB may not feel ill at first. Early symptoms may be subtle and, if the TB is extrapulmonary (outside of the lungs in organs such as the kidney and bone), the tuberculosis may be fairly advanced by the time it causes noticeable symptoms.
2. What is the difference between MDR TB and XDR TB?
Both indicate strains of M. tuberculosis that can be difficult to treat, but XDR TB is resistant to more drug therapies. XDR TB is currently defined by the CDC (Centers for Disease Control and Prevention) and WHO (World Health Organization) as M. tuberculosis that is resistant to isoniazid and rifampin, plus resistant to any fluoroquinolone and to at least one of three injectable “second-line” drugs (amikacin, kanamycin, or capreomycin). The emergence of XDR TB is being closely watched by the world medical community and measures are being taken in hopes of limiting its spread.
3. Why is the doctor asking me to take my TB medication in the presence of a nurse?
Direct observed therapy (DOT) ensures that the patient is taking their medications and continuing their therapy for the required length of time. Unlike other bacterial infections that can be cured in 7-10 days, TB must be treated with two or more drugs for several months.
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This article was last reviewed on
March 4, 2007.
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