Extensively drug-resistant Mycobacterium tuberculosis

Definition

Extensively drug-resistant Mycobacterium tuberculosis (XDR-TB) is a form of tuberculosis that is resistant to at least four of the core anti-TB drugs. This makes it more difficult to treat and control compared to other forms of TB.

5 Must Know Facts For Your Next Test

1. XDR-TB is resistant to isoniazid and rifampin, which are the two most powerful first-line treatment anti-TB drugs.
2. It is also resistant to any fluoroquinolone and at least one of three injectable second-line drugs (amikacin, kanamycin, or capreomycin).
3. The development of XDR-TB is primarily due to improper use of antibiotics and incomplete or incorrect treatment regimens.
4. Diagnosing XDR-TB requires advanced laboratory tests that can detect drug resistance patterns.
5. Treatment options for XDR-TB are limited, often longer in duration, more toxic, and less effective than standard TB treatments.

Review Questions

• What are the primary first-line drugs to which XDR-TB shows resistance?
• How does improper use of antibiotics contribute to the development of XDR-TB?
• Why is diagnosing XDR-TB more challenging compared to other forms of TB?

Related terms

Multidrug-resistant Tuberculosis (MDR-TB): A form of TB that is resistant to at least isoniazid and rifampin.

Antimicrobial Resistance:

The ability of a microbe to withstand the effects of medication previously used to treat them.

Second-line Drugs: Medications used when first-line treatments fail due to resistance or intolerance.