A modified decontamination and storage method for sputum from patients with tuberculosis

Area of Science:

• Microbiology
• Clinical Diagnostics
• Public Health

Background:

• Efficient handling of sputum samples is crucial for future Mycobacterium tuberculosis (M.tb) culturing.
• Current methods require optimization for maximized storage and M.tb recovery.
• Minimizing laboratory workload and contamination risk is essential for large-scale sample processing.

Purpose of the Study:

• To develop and evaluate a modified sputum digestion and decontamination method.
• To assess the impact of the modified method on storage capacity, M.tb recovery, and laboratory efficiency.
• To compare the modified method with the standard N-Acetyl-L-cysteine and sodium hydroxide (NALC-NaOH) method.

Main Methods:

• Sputum samples from pulmonary tuberculosis patients were processed using both standard NALC-NaOH and a modified method.
• Processed samples were frozen and subsequently cultured in BD BACTEC 960 Mycobacterium Growth Indicator Tubes (MGIT).
• Time to Positivity (TPP) and Growth Unit (GU) data were analyzed, along with contamination rates.

Main Results:

• The modified method resulted in longer TPP (p < 0.05) but similar GU compared to the standard method.
• A low failure rate (1/22) was observed with the modified method in initial comparative testing.
• In a larger cohort (348 samples), the modified method showed a 90.5% MGIT positive rate, 7.8% negative rate, and 1.7% contamination rate, with no significant impact from storage duration or smear grade.

Conclusions:

• The modified sputum processing method is effective for collecting and storing large numbers of samples over extended periods.
• It achieves acceptable M.tb recovery rates and maintains a low risk of contamination.
• This method offers a viable solution for large-scale M.tb sample management for future diagnostic and research purposes.