AFB Susc. Levofloxacin

This test determines whether acid-fast bacilli (AFB), most commonly Mycobacterium tuberculosis, are susceptible or resistant to the antibiotic levofloxacin. It is a type of drug susceptibility test (DST) used in tuberculosis (TB) diagnosis and treatment planning. Levofloxacin is a fluoroquinolone often used in multidrug-resistant TB regimens.

 Knowing whether the TB bacteria are resistant to levofloxacin allows for tailored treatment plans and prevents the use of ineffective drugs. With rising rates of drug-resistant TB worldwide, such testing is essential for choosing the most effective antibiotics and curbing disease spread.

It is usually performed after an AFB culture has tested positive and is confirmed to be Mycobacterium tuberculosis. It is essential in patients with a history of TB treatment, suspected drug resistance, or when starting a multidrug regimen for TB.

A “susceptible” result means the TB strain will likely respond to levofloxacin treatment. A “resistant” result indicates the bacteria are unlikely to respond, and alternative antibiotics should be considered. This result plays a major role in developing an effective treatment regimen.

A culture of the TB organism is grown from a patient’s sputum or tissue sample and exposed to levofloxacin in a controlled laboratory setting. Growth patterns are then observed to determine resistance.