Comparison of chlorhexidine 0.7% and modified Petroff's method on sputum decontamination for culture method to detect Mycobacterium tuberculosis

Abstract

Background: Tuberculosis (TB) is an infectious disease that is the leading cause of death from a single infectious agent worldwide. Culture is still the gold standard for the diagnosis of pulmonary TB. As an important specimen, sputum is often contaminated by normal flora at the time of collection, making the decontamination process an essential step of Mycobacterium tuberculosis culture. Decontamination with chlorhexidine 0.7% is expected to improve the detection of Mycobacterium tuberculosis in the culture method better than Modified Petroff's method. Methods: This research is an experimental study. Sputum was collected from pulmonary TB patients. Each sputum was decontaminated with chlorhexidine 0,7% and others with Modified Petroff's. Decontaminated sputum inoculated on Lowenstein-Jensen media. Samples were incubated, and evaluated the recovery rate of Mycobacterium tuberculosis. Data were analyzed using SPSS version 25.0 for Windows. Results: In total, we collected 16 sputum with 11 (68.75%) direct smear positive, 14 (87.5%) smear positive by chlorhexidine 0.7% method, and 13 (81.25%) by Modified Petroff's method. The number of cultures positive for Mycobacterium tuberculosis by chlorhexidine 0.7% method was 14 (87.5%), of which 11 (68.75%) have specific colony characteristics of Mycobacterium tuberculosis, 3 (18.75%) non-tuberculous mycobacteria, and 1 (6.24%) mixed. In Modified Petroff's, 6 (37.5%) were positive cultures and showed only growth of Mycobacterium tuberculosis. The contamination rate was 1 (6.25%) using chlorhexidine 0.7% and 8 (50%) using Modified Petroff’s method. Conclusion: Chlorhexidine 0.7% has a higher recovery rate in the culture of Mycobacterium tuberculosis compared with Modified Petroff's, showing recovery of non-tuberculous mycobacteria and a lower contamination rate.