What does a positive AFB test mean?

If your AFB culture was positive, it means you have active TB or another type of AFB infection. The culture can identify which type of infection you have. Once you have been diagnosed, your provider may order a "susceptibility test" on your sample.

What does positive AFB mean?

A positive AFB smear or culture several weeks after drug treatment has started may mean that the treatment regimen is not effective and needs to be changed. It also means that the person is still likely to be infectious and can pass the mycobacteria to others through coughing or sneezing.

What disease is normally associated with AFB?

Acid-fast bacilli (AFB) smear-positive sputum is usually an initial clue in the diagnosis of pulmonary tuberculosis (TB); however, the test is not disease-specific.

How accurate is AFB test?

RESULTS: Diagnostic accuracy of induced sputum AFB smear was found to be 92.85%, sensitivity 63.63%, specificity 97.26%, PPV 77.78% and NPV 95.67% (p-value <0.001)and that of BAL was found to be 86.90%, sensitivity 52.94%, specificity 95.52%, PPV 75% and NPV 88.89% (p-value <0.001).

How do you read AFB results?

Grading AFB scale (WHO-IUATLD)

Note that seeing 1-9 AFB per 100 HPF is reported as “scanty” and the exact number of bacilli should be recorded. For example, a report of “scanty 3” means there were three AFB seen per 100 HPFs and is not the same as a report of “AFB 3+”. Scanty results are considered as positive result.

Doctor explains Acid-Fast Bacilli (AFB) test | Mycobacterium Tuberculosis (TB)

What are some diseases caused by acid-fast bacteria?

Tuberculosis, Leprosy and Other Diseases Caused by Acid-Fast Bacteria.

What diseases can be diagnosed through the acid-fast procedure?

An acid-fast bacteria (AFB) culture is done to find out if you have tuberculosis (TB) or another mycobacterial infection. Besides TB, the other main mycobacterial infections are leprosy and a TB-like disease that affects people with HIV/AIDS.

What can cause a positive AFB?

If your AFB smear was positive, it means you probably have TB or other infection, but an AFB culture is needed confirm the diagnosis. Culture results can take several weeks, so your provider may decide to treat your infection in the meantime.

Does a positive acid-fast stain result always indicate infection with Mycobacterium tuberculosis?

AFB-microscopy is indicated for suspected cases of tuberculosis. Positive microscopy confirms the presence of acid-fast bacilli. Care must be taken not to interpret positive results as M. tuberculosis because the Ziehl-Neelsen and auramine stains only indicate the presence of acid-fast bacteria/structures.

What happens if sputum test is positive?

For the smear, lab staff will look at some of your sputum under a microscope. If they see bacteria in your sputum, the smear test result is positive. For the culture, lab staff put some of your sputum into a special container to grow. If bacteria grow, your culture result is positive.

What does AFB mean in medical terms?

Acid- Fast Bacilli (AFB) smear and culture are two separate tests always performed together at the MSPHL, Tuberculosis (TB) Unit. AFB smear refers to the microscopic examination of a fluorochrome stain of a clinical specimen.

Is AFB gram-positive?

Acid-fast bacteria are gram-positive, but in addition to peptidoglycan, the outer membrane or envelope of the acid-fast cell wall of contains large amounts of glycolipids, especially mycolic acids that in the genus Mycobacterium, make up approximately 60% of the acid-fast cell wall (Figure 2.3C. 2).

Can TB be cured?

With treatment, TB can almost always be cured. A course of antibiotics will usually need to be taken for 6 months. Several different antibiotics are used because some forms of TB are resistant to certain antibiotics.

Is latent TB contagious?

A person who has been exposed to TB bacteria may become infected. A person with latent TB infection (LTBI) cannot spread the bacteria to others right away. Only those who develop active TB disease can spread the bacteria to others.

What does a positive acid-fast stain mean?

A positive result means that bacteria were found and that you may have an infection. The smear is treated with a special acid-fast stain that can provide a preliminary test result in 24 hours. At the same time, another sample of sputum is also tested as a culture.

Would an acid-fast stain be informative for diagnosis?

The acid-fast stain would not be informative since the cell wall of S. pyogenes stains Gram-positive, and the rapidly growing pathogen rapidly responds to drug treatment.

What does an acid-fast stain tell you?

The acid-fast stain is a laboratory test that determines if a sample of tissue, blood, or other body substance is infected with the bacteria that causes tuberculosis (TB) and other illnesses.

Can AFB be false positive?

Some sputum can be positive in the AFB smear but negative in mycobacterial culture because of nonviable bacilli during successful anti-TB medication, and the possibility of a false-positive AFB smear or alternative diagnosis other than mycobacterial diseases cannot be excluded (4, 6-8).

What bacteria causes tuberculosis?

Tuberculosis (TB) is a contagious disease caused by infection with Mycobacterium tuberculosis (Mtb) bacteria. It is spread through the air when a person with TB disease of the lungs or throat coughs, speaks or sings, and people nearby breathe in these bacteria and become infected.

What the causes of false positive acid-fast smears?

Exposure to direct sunlight and the excessive heat can also destroy a significant number of acid-fast bacilli in the sputum sample, thereby rendering the results compromised. Analytical factors such as poor smearing, staining, and microscopy can also hamper the results of acid-fast microscopy.

What color would bacterial cells appear if the patient has tuberculosis?

The purple rod-shaped organism is a TB bacterium. This name, meaning 'fungus-bacteria' refers to shape of the bacillus when it grows in a laboratory: when seen through a microscope it forms heaps of small rods with protective layers around them, and thus looks like a fungus.

Why is AFB called acid-fast?

Mycobacterium and many Nocardia species are called acid-fast because during an acid-fast staining procedure they retain the primary dye carbol fuchsin despite decolorization with the powerful solvent acid-alcohol. Nearly all other genera of bacteria are nonacid-fast.

How long does it take to get AFB culture results?

With the exception of 4 clinical specimens out of 24 AFB-positive specimens, the broth medium expectedly allowed the most rapid growth. Irrespective of smear results, the mean time to detection (TTD) in the MGIT broth was 15.3 days for all mycobacteria, 17.1 days for the M.

Is E coli and acid-fast bacteria?

Therefore, these organisms are said to be “acid-fast”. Most bacteria, such as E. coli and Staphylococcus, lack this high mycolic acid content and are easily decolorized by the acid-alcohol. Therefore, these organisms are described as “non-acid-fast”.

What bacteria is acid-fast positive?

The acid fast bacterial cell envelope is a specialized derivation of the Gram-positive cell envelope that has an extremely high lipid content. Acid-fast bacteria include the Mycobacteria and some of the Nocardia.