Evaluation of Omnigene Sputum, A Novel Sputum Transport and Decontamination Reagent for Microscopy, Culture and Dna-Based Assays

Abstract

Tuberculosis (TB), continues to kill millions of people each year. Sputum culture for laboratory confirmation of TB diagnosis and treatment monitoring is limited to centralized facilities. Thus, samples require transportation from peripheral laboratories to these facilities, which compromises specimen quality since it is difficult to maintain cold chain. This project evaluated Omnigene Sputum reagent (OMS) for preserving sputa in transport. One hundred and four sputa were collected from clinically diagnosed TB patients. Sputum contaminants were first characterized using blood agar cultures and MALDI-ToF MS then sputa were decontaminated with NALC-NaOH and OMS. The treated samples were first inoculated on blood agar to isolate persisting contaminants, then on Lowenstein Jensen (LJ) media for mycobacteria recovery before smears were prepared for microscopy. The compatibility of OMS for molecular analysis was determined using Xpert MTB/RIF analysis. Before decontamination, 89.4% sputa had bacterial growth on blood agar and 4.8% and 5.8% still had contaminants after OMS and NALC-NaOH treatment respectively. On LJ media, higher contamination rate was recorded for NALC-NaOH (12.8%) samples than for OMS (4.3%) samples. However, mycobacteria positivity was comparable between both methods: OMS; 78.7% and NALC-NaOH 74.4%. Acid fast bacilli positivity after OMS and NALC-NaOH treatment was 89.4% and 75.9% respectively and 97.9% of the samples analyzed by Xpert MTB/RIF assay after each of the treatments were positive for MTBC with no detection of rifampicin resistance. Findings from this project clearly show that OMS can effectively be used as a sputum transport and decontamination reagent in Ghana, however I will recommend for further work involving field-testing.