Clinical evaluation of the novel molecular bacterial load assay for real-time monitoring of tuberculosis treatment response

Monitoring the treatment of tuberculosis (TB) relies on less sensitive smear microscopy (SM) and culture methods which are very slow. We evaluated the novel Molecular bacterial load assay (MBLA) for implimentability and real-time monitoring of TB treatment in a clinical setting.

Therapy naive (Xpert MTB/RIF confirmed) TB positive patients were enrolled in Mbeya, Tanzania. Sputum samples were collected at baseline and thereafter at week 2, month 2, 5 and 6 of treatment. Samples were analysed for M. tuberculosis (M.tb) by MBLA and compared to SM, culture and clinical monitoring.

59 TB patients were enrolled for the study. Median age, 37 (18-65) years, 62.7 % (37/59) male, 45.6 % (27/59) HIV positive and 8.47 % (5/59) were re-treatment. Mean BL (± SD) at baseline was 5.48 ± 1.3 declining to 3.42 ± 0.7  at month 2 and 3.51 ± 0.62 log10CFU/ml at month 6 of treatment. This corresponds MBLA positivity of 92.98, 65.5 and 7.84 % at baseline, month 2 and 6 respectively. In contrast, positivity of SM and culture were 78.95, 9.62 and 0 %, and 85.96, 25 and 3.39 % at baseline, month 2 and 6 respectively. Decline in test positivity reflected resolution of clinical signs. While night sweat, and chest pain resolved earlier on in treatment, resolution of cough was slow and consistent with MBLA. Furthermore, the turn-around-time for MBLA results was 24  h compared to median (range) of 14.83 (4.33–42)  days for liquid culture.

MBLA exhibited higher sensitivity and shorter turn-around-time than standard tests and clinical signs. This demonstrates the potential of MBLA to offer real-time results for clinical decision making.