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Comparative Study
. 2025 Feb;90(2):106399.
doi: 10.1016/j.jinf.2024.106399. Epub 2024 Dec 27.

The molecular bacterial load assay predicts treatment responses in patients with pre-XDR/XDR-tuberculosis more accurately than GeneXpert Ultra MTB/Rif

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Free article
Comparative Study

The molecular bacterial load assay predicts treatment responses in patients with pre-XDR/XDR-tuberculosis more accurately than GeneXpert Ultra MTB/Rif

Marit Neumann et al. J Infect. 2025 Feb.
Free article

Abstract

Objectives: Early detection of treatment failure is essential to improve the management of drug-resistant tuberculosis (DR-TB). We evaluated the molecular bacterial load assay (MBLA) in comparison to standard diagnostic tests for monitoring therapy of patients affected by drug-resistant TB.

Methods: The performance of MBLA in tracking treatment response in a prospective cohort of patients with pulmonary MDR/RR- and pre-XDR/XDR-TB was compared with mycobacterial culture, mycobacterial DNA detection using GeneXpert (Xpert) and microscopy detection of sputum acid-fast-bacilli.

Results: Mycobacterium tuberculosis culture conversion was used as the read-out for treatment responses. The MBLA was most concordant during the early phase of treatment, detecting changes in bacterial load with similar accuracy to microscopy and outperforming Xpert. When considering all timepoints, concordance with MGIT results was 72.1% for MBLA, 57.4% for Xpert and 76.7% for microscopy. The AUC for culture conversion was higher for MBLA (0.88, CI 0.84-0.95) than for Xpert (0.78, CI 0.72-0.85) and microscopy (0.77, CI 0.71-0.83).

Conclusions: MBLA was superior in the early identification of successful culture conversion compared to microscopy and Xpert and could be a useful biomarker to evaluate novel entities in Phase IIA early-bactericidal-activity drug trials regardless of the degree of M. tuberculosis drug resistance.

Keywords: Diagnostic evaluation; Drug-resistant tuberculosis; Molecular bacterial load assay (MBLA); Pulmonary tuberculosis.

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Conflict of interest statement

Declaration of Competing Interest J.H. received a honorarium for lectures from Chiesi, Böhringer Ingelheim, and Sanofi, which have nothing to do with the content of this manuscript. C.L. has received an honorarium for consultation service to INSMED, a company that produced liposomal amikacin as an inhalation suspension for the treatment of NTM-PD outside of the scope of this work. He received speakers’ honoraria from INSMED, GSK, Gilead, Astra Zeneca, MedUpdate and MedUpdateEurope outside of the scope of this study. All other authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

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