Antibiogram – MTB (Ethionamide)

Tuberculosis or TB, caused by Mycobacterium tuberculosis (MTB) is one of the diseases with a high fatality rate that mostly affects the lungs (Pulmonary TB) and sometimes affects other components like pleura, joints, abdomen, skin, etc (Non-pulmonary TB). The disease spreads when the bacteria are dispersed in the air when an infected person spits, coughs, or sneezes. Due to the slow growth pattern and drug resistance, the disease presents a major challenge in terms of treatment and quick diagnostic techniques.

Antibiogram test or Antimicrobial Susceptibility testing is performed to measure the susceptibility of microbes to certain antibiotics. Antibiogram – MTb (Ethionamide) test checks for the sensitivity or resistance of MTB to the antibiotic – Ethionamide. Ethionamide, a nicotinamide derivative is a second-line drug that belongs to the thioamides group of antibiotics and is used with other medications to treat drug-resistant tuberculosis (TB) infection. The concentration of the drug determines whether it has bactericidal or bacteriostatic action on susceptible organisms and is believed to inhibit mycolic acid synthesis.

Cough for more than three weeks, chills, fever, night sweats, loss of appetite, weakness, and weight loss are some of the symptoms observed in individuals suffering from TB infection.

Why and when get tested with Antibiogram – MTB (Ethionamide) test?
Antibiogram – MTB (Ethionamide) test is used for determining and monitoring drug susceptibility pattern of Mycobacterium tuberculosis, the bacterium that is responsible for Tuberculosis against the antibiotic – Ethionamide. This test is needed if an infection has shown to have antibiotic resistance, is otherwise hard to treat, or if there’s a bacterial or fungal infection that is not responding to standard treatments.

What is an Antibiogram test?
Antibiogram test 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.

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, and 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: 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).

What is the role of Ethionamide in Tuberculosis treatment?
Ethionamide, derived from nicotinamide is used as a second-line drug in treating drug-resistant TB infections. The concentration of the drug determines whether it has bactericidal or bacteriostatic action on organisms that cause TB.