Rapid drug susceptibility testing of Mycobacterium tuberculosis using conventional solid media

Area of Science:

• Microbiology
• Infectious Diseases
• Clinical Diagnostics

Background:

• Standard Mycobacterium tuberculosis drug susceptibility testing (DST) is time-consuming, often taking weeks to months.
• Rapid DST methods exist but typically require expensive, sophisticated equipment, limiting their accessibility.
• Effective tuberculosis treatment relies on prompt susceptibility results to guide appropriate drug selection.

Purpose of the Study:

• To evaluate a simplified, rapid agar-dilution method for Mycobacterium tuberculosis drug susceptibility testing.
• To assess the speed, practicality, and cost-effectiveness of this method compared to standard techniques.
• To determine the accuracy of the rapid method for detecting resistance to key anti-tuberculosis drugs.

Main Methods:

• A simplified agar-dilution method using Middlebrook 7H11 agar and microcolony detection was employed.
• Testing was performed on sputum from 197 patients with pulmonary tuberculosis (64 smear-positive, 70 smear-negative).
• Additional clinical specimens (bronchoscopy, biopsy, pleural, gastric fluid) from 63 patients were also analyzed.

Main Results:

• Median time to results was significantly reduced: 11 days for smear-positive and 35 days for smear-negative patients, versus 62-72 days for standard methods.
• The rapid method accurately identified all cases of single-drug and multidrug resistance within 13-38 days.
• High accuracy was demonstrated with only one discrepancy in 985 resistance tests, and no observed contamination.

Conclusions:

• The rapid Mycobacterium tuberculosis susceptibility testing method on Middlebrook 7H11 agar is fast, practical, and inexpensive.
• This method offers a viable alternative to sophisticated techniques, especially in resource-limited settings.
• The approach facilitates quicker identification of drug resistance, enabling more timely and effective tuberculosis treatment.