Comparison of Power Ultrasound and NALC-NaOH Decontamination Methods for Stool Mycobacterial Culture: A Prospective Study

Abstract

Stool samples have been reported to be useful for the diagnosis of pulmonary tuberculosis (PTB), especially in patients who are unable to produce sputum. However, contamination limits the usefulness of stool specimens in mycobacterial culture. In this study, a novel decontamination method of power ultrasound (PU) was evaluated for mycobacterial isolation from suspected PTB cases. Stool samples (n = 650) were collected, and each sample was divided into approximately three equal groups. In addition to an AFB smear (Auramine O method), the stool samples were treated using different decontamination methods (NaOH-NALC vs. PU methods). The sensitivity (calculated against CRS) and contamination rates between the two methods were compared using McNemar’s test. Of the 650 samples, 32 (4.92%) stool samples treated with the NaOH-NALC method were culture-positive, including Mycobacterium tuberculosis (M.TB; n = 21, 3.23%) and nontuberculous mycobacteria (NTM; n = 11, 1.69%). Sixty-one (9.38%) stool samples treated with the PU method were culture-positive, including M.TB (n = 37, 5.69%) and NTM (n = 24, 3.69%). Statistical analysis showed that a significant difference was found in the isolation rate of M.TB and NTM between the two methods (p < 0.05). Additionally, compared with the NALC-NaOH method (19.07%), stool samples treated with the PU method (13.23%) had a significantly lower contamination rate (p < 0.05). In conclusion, our findings suggest that the utilization of the PU method as a novel decontamination technique could significantly enhance the isolation rates of both NTM and M.TB when stool specimens are employed for culture. Compared to the NaOH-NALC method, this approach proves to be more effective in facilitating stool mycobacterial culture.