AFB Drug Susceptibility (SIRE) 1st Line

AFB denotes Acid-fast bacteria, also called acid-fast bacilli. These are a group of bacteria sharing the property of acid fastness, that is the physical ability to resist decolorization by acids during staining procedures. This unique feature serves as a distinguishing ability in classifying and detecting acid-fast bacteria like Mycobacteria.

Tuberculosis or TB, caused by the bacterium Mycobacterium tuberculosis (MTB) is one of the diseases with a high fatality rate. Susceptibility testing is important due to the emergence of drug resistance in the bacterium. The AFB drug susceptibility test is used to determine the sensitivity of AFB culture to different types of antibiotics to determine whether the bacteria are sensitive or resistant to antibiotics.

In the AFB Drug susceptibility (SIRE) 1st line test, susceptibility of the acid-fast bacilli (Mycobacterium tuberculosis) is tested against the first-line drugs -Streptomycin, Isoniazid, Rifampicin, and Ethambutol used for the treatment of TB. This test is useful in providing effective treatment for individuals suffering from TB.

Why get tested with AFB Drug Susceptibility (SIRE) 1^st Line?

AFB Drug Susceptibility (SIRE) 1^st Line is performed to detect drug-resistant Tuberculosis. This test can identify the sensitivity of MTB against first-line drugs like Streptomycin, Isoniazid, Rifampicin, and Ethambutol

What is a drug susceptibility test?
Drug susceptibility test (DST) or Antibiotic susceptibility testing (AST) is a widely-used technique for evaluating antibiotic resistance and determining the most effective antibiotic for treatment. This is achieved by observing the effect of a particular antibiotic on microbial growth. The treatment can be directed as per the knowledge of the microbe and its sensitivity to the drug.

https://medlineplus.gov/lab-tests/antibiotic-sensitivity-test/

https://tbfacts.org/drug-susceptibility/

What sample is required and what preparation is needed for this test?
A pure culture obtained from body fluids, sputum, bronchial alveolar lavage, cerebrospinal fluid (CSF), pus, tissue, biopsies, lymph nodes, abscess, urine is used for performing this test. There is no special preparation required before getting this test.

What are the types of drug-resistant TB?
Drug-resistant tuberculosis infection, caused by drug-resistant Mycobacterium tuberculosis (MTB) bacterium is divided into the following categories

• Multidrug-resistant or MDR-TB: MDR-TB is the TB infection caused by MTB that is resistant to the most potent drugs used in TB treatment – isoniazid and rifampin.
• Extensively drug-resistant or XDR-TB: XDR-TB is the TB infection caused by MTB that is resistant to most commonly used drugs used in TB treatment like isoniazid and rifampin, plus any fluoroquinolone as well as at least one of the three injectable second-line drugs (amikacin, kanamycin, and capreomycin).

https://www.cdc.gov/tb/topic/drtb/default.htm

What does SIRE stand for?
SIRE is short for first-line drugs Streptomycin, Isoniazid, Rifampicin, Ethambutol.