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Original Research ARTICLE Provisionally accepted The full-text will be published soon. Notify me

Front. Microbiol. | doi: 10.3389/fmicb.2019.02381

Differential culturability of Mycobacterium tuberculosis in culture-negative sputum of patients with pulmonary tuberculosis and in a simulated model of dormancy

 Azger Dusthackeer1*, Magizhaveni Balasubramanian1, Shanmugam Govindarajan1, Shanmuga Priya2,  Christy R. Nirmal1,  Sam E. Rajadas1, Angayarkanni Balasubramanian1, Rajesh K. Mondal1,  Kannan Thiruvenkadam1, A K. Hemanth Kumar1, Geetha Ramachandran1 and  Selvakumar Subbian3*
  • 1National Institute of Research in Tuberculosis (ICMR), India
  • 2National Institute of Epidemiology (ICMR), India
  • 3Public Health Research Institute (PHRI), United States

Tuberculosis (TB) remains a leading killer among infectious diseases of humans worldwide. Delayed diagnosis is a key problem in global TB control programs. Bacteriological methods currently used to diagnose TB in endemic countries takes up to 8 weeks that poses significant delay in starting antibiotic therapy. Presence of a heterogeneous population of Mycobacterium tuberculosis, the causative agent of TB, is among the reasons for delayed diagnosis by bacteriological methods. Previously, it has been shown that mycobacterial resuscitation promoting factors (RPF), a family of proteins secreted by actively growing bacteria into the media, are capable of activating the growth of dormant bacteria, thus enhancing the detection of bacilli in the sputum of confirmed TB cases. However, the variability in bacterial resuscitation by RPF in the sputum of suspected pulmonary TB cases that showed differential smear and/or culture positivity during diagnosis has not been fully explored. Here, we report the presence of non-replicating bacteria in the sputum of suspected TB cases that show differential growth response to RPF treatment. Using crude and recombinant RPF treatment, we show improved sensitivity and reduced time to detect bacilli in the sputum samples of smear-positive/culture-negative or smear-negative/culture-negative cases. We also report the phenotypic heterogeneity in the RPF-responsiveness among Mtb strains using an in vitro dormancy model. Our findings have implications for improving the bacteriological diagnostic modalities currently used to diagnose TB in endemic countries.

Keywords: Tuberculosis, Bacteriological diagnosis, Resuscitation, Mycobacteirum tuberculosis, Clinical isolate organism, sputum samples, dormancy

Received: 19 Aug 2019; Accepted: 01 Oct 2019.

Copyright: © 2019 Dusthackeer, Balasubramanian, Govindarajan, Priya, Nirmal, Rajadas, Balasubramanian, Mondal, Thiruvenkadam, Hemanth Kumar, Ramachandran and Subbian. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence:
Mx. Azger Dusthackeer, National Institute of Research in Tuberculosis (ICMR), Chennai, Tamil Nadu, India, azger@nirt.res.in
Mx. Selvakumar Subbian, Public Health Research Institute (PHRI), Newark, United States, subbiase@njms.rutgers.edu