Molecular Bacterial Load Assay Concurs with Culture on NaOH-Induced Loss of Mycobacterium tuberculosis Viability [Mycobacteriology and Aerobic Actinomycetes]

Effective methods to detect viable Mycobacterium tuberculosis, the main causative agent of tuberculosis (TB), are urgently needed. To date, cultivation of M. tuberculosis is the gold standard, which depends on initial sample processing with N-acetyl-l-cysteine–sodium hydroxide (NALC-NaOH), chemicals that compromise M. tuberculosis viability and, consequently, the performance of downstream tests. We applied culture and the novel molecular bacterial load assay (MBLA) to measure the loss of M. tuberculosis viability following NALC-NaOH treatment of M. tuberculosis H37Rv pure culture and clinical sputum samples from pulmonary TB patients. Compared to the bacterial loads of untreated controls, NALC-NaOH treatment of M. tuberculosis reduced the MBLA-detectable bacillary load (estimated number of CFU [eCFU] per milliliter) by 0.66 ± 0.21 log10 at 23°C (P = 0.018) and 0.72 ± 0.08 log10 at 30°C (P = 0.013). Likewise, NALC-NaOH treatment reduced the viable count on solid culture by 0.84 ± 0.02 log10 CFU/ml at 23°C (P < 0.001) and 0.85 ± 0.01 log10 CFU/ml at 30°C (P < 0.001), respectively. The reduction in the viable count was reflected by a corresponding increase in the time to positivity of the mycobacterial growth indicator tube (MGIT) liquid culture: 1.2 days at 23°C (P < 0.001) and 1.1 days at 30°C (P < 0.001). This NaOH-induced M. tuberculosis viability loss was replicated in clinical sputum samples, with the ba...

Source: Journal of Clinical Microbiology - June 24, 2019 Category: Microbiology Authors: Mtafya, B., Sabiiti, W., Sabi, I., John, J., Sichone, E., Ntinginya, N. E., Gillespie, S. H. Tags: Mycobacteriology and Aerobic Actinomycetes Source Type: research