Modification of proportion sensitivity testing method for ethionamide.

Area of Science:

• Microbiology
• Infectious Diseases
• Clinical Diagnostics

Background:

• Standardized drug susceptibility testing (DST) is essential for treating multidrug-resistant tuberculosis (MDR-TB).
• Ethionamide, a second-line bacteriostatic drug, presents challenges in laboratory testing and clinical interpretation.
• Optimizing DST methods for drugs like ethionamide is critical for effective MDR-TB management.

Purpose of the Study:

• To optimize the standard proportion sensitivity testing (PST) method for ethionamide.
• To evaluate the efficacy of ethionamide DST using standard (40 μg/ml) and an additional higher concentration (57 μg/ml).

Main Methods:

• The study analyzed 235 Mycobacterium tuberculosis isolates from new and previously treated pulmonary tuberculosis patients.
• The standard proportion sensitivity testing (PST) method was employed.
• Ethionamide concentrations of 40 μg/ml and 57 μg/ml were evaluated.

Main Results:

• Performance parameters and agreement between the 40 μg/ml and 57 μg/ml ethionamide concentrations were high.
• The PST method demonstrated efficiency at the standard 40 μg/ml concentration.
• The additional 57 μg/ml concentration offers a viable alternative for ethionamide susceptibility testing.

Conclusions:

• The standard proportion sensitivity testing (PST) method is effective for ethionamide susceptibility testing in Mycobacterium tuberculosis.
• Both 40 μg/ml and 57 μg/ml concentrations show good performance, with the higher concentration serving as a useful alternative.
• Optimized DST for ethionamide can improve the treatment of multidrug-resistant tuberculosis.