OMNIgene.SPUTUM suppresses contaminants while maintaining Mycobacterium tuberculosis viability and obviates cold-chain transport

Abstract

Tuberculosis (TB) diagnostics are centralised, requiring long-distance transportation of specimens in most resource-limited settings. We evaluated the ability of OMNIgene.SPUTUM (OM-S) to obviate cold-chain transport of TB specimens. A two-arm (same-day and after 5 days sample processing) study was conducted to assess contamination rates and Mycobacterium tuberculosis viability in OM-S-treated samples against the standard decontamination procedure (SDP) in Mozambique, using Lowenstein Jensen (LJ) and mycobacterial growth indicator tube (MGIT) culture and molecular bacterial load assay. 270 specimens were processed using OM-S and SDP in same-day and 5-day arms. Contamination was lower in OM-S-treated than SDP-treated cultures: 12% versus 15% and 2% versus 27% in the same-day and 5-day arms, respectively. M. tuberculosis recovery in OM-S-treated LJ cultures was 10% and 56% higher in the same-day and 5-day arms, respectively, than SDP-treated cultures, but lower in MGIT (52% and 28% lower in the same-day and 5-day arms, respectively). M. tuberculosis viable count was 1log estimated CFU·mL^-1 lower in 5-day OM-S-treated sputa. OM-S was more effective at liquefying sputum with a shorter sample processing time: 22 min for culture. OM-S is simple to use and has demonstrated a high potency to suppress contaminants, maintenance of viability at ambient temperatures and higher M. tuberculosis recovery, particularly in the solid LJ cultures. Optimisation of OM-S to achieve higher MGIT culture positivity and shorter time to result will increase its application and utility in the clinical management of TB.

FIGURE 1

Difference in Mycobacterium growth indicator tube (MGIT) times to culture positivity (TTP) for the two groups in each study arm. Bars represent median values. SDP: standard decontamination procedure; SD: same-day arm; OM-S: OMNIgene.SPUTUM procedure; 5D: 5-day arm.

FIGURE 2

Difference in Lowenstein Jensen (LJ) times to culture positivity (TTP) for the two groups in each study arm. Bars represent median values. SDP: standard decontamination procedure; SD: same-day arm; 5D: 5-day arm; OM-S: OMNIgene.SPUTUM procedure.

FIGURE 3

Differences in viable bacterial load count by molecular bacterial load assay for the two groups in each study arm. Bars represent median values. CRL: control; SD: same-day arm; 5D: 5-day arm; OM-S: OMNIgene.SPUTUM procedure.

FIGURE 4

The correlation between Mycobacterium growth indicator tube (MGIT) time to culture positivity (TTP) and bacterial load count by molecular bacterial load assay for a) standard decontamination procedure-treated samples and b) OMNIgene.SPUTUM-treated samples.