Molecular Bacterial Load Assay, a Culture-Free Biomarker for Rapid and Accurate Quantification of Sputum Mycobacterium tuberculosis Bacillary Load during Treatment

Isobella Honeyborne, Timothy D. McHugh, Patrick Phillips, Selina Bannoo, Anna Bateson, N Carroll, Felicity Perrin, Katharina Ronacher, Laura Wright, Paul van Helden, Gerhart Walzl, Stephen Henry Gillespie

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86 Citations (Scopus)

Abstract

A molecular assay to quantify Mycobacterium tuberculosis is described. In vitro, 98% (n = 96) of sputum samples with a known number of bacilli (107 to 102 bacilli) could be enumerated within 0.5 log10. In comparison to culture, the molecular bacterial load (MBL) assay is unaffected by other microorganisms present in the sample, results are obtained more quickly (within 24 h) and are seldom inhibited (0.7% samples), and the MBL assay critically shows the same biphasic decline as observed longitudinally during treatment. As a biomarker of treatment response, the MBL assay responds rapidly, with a mean decline in bacterial load for 111 subjects of 0.99 log10 (95% confidence interval [95% CI], 0.81 to 1.17) after 3 days of chemotherapy. There was a significant association between the rate of bacterial decline during the same 3 days and bacilli ml−1 sputum at day 0 (linear regression, P = 0.0003) and a 3.62 increased odds ratio of relapse for every 1 log10 increase in pretreatment bacterial load (95% CI, 1.53 to 8.59).
Original languageEnglish
Pages (from-to)3905-3911
JournalJournal of Clinical Microbiology
Volume49
Issue number11
DOIs
Publication statusPublished - Nov 2011

Keywords

  • tuberculosis
  • biomarkers
  • bacteriological load
  • therapeutics

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