Evidence of nitrite acting as a stable and robust inducer of non-cultivability in Mycobacterium tuberculosis with physiological relevance

Abstract

Tuberculosis (TB) is the ninth leading cause of death worldwide, ranking above human immunodeficiency virus. Latency is the major obstacle in the eradication of this disease. How the physiology of the pathogen changes in transition to the latent stage needs to be understood. The latent bacteria extracted from animal hosts exist in a nonculturable (NC) phase, whereas bacteria extracted from most in vitro models are culture-positive. In the present study, we observed that nitrite, up to a concentration of 5 mM, shows the growth of Mycobacterium tuberculosis (MTB) in liquid media, but this effect starts reversing at higher concentrations. At a concentration of 10 mM, nitrite induces rapid nonculturability of MTB at the aerobic stage. This noncultivable dormancy was confirmed by analyzing the characteristics of NC bacteria. Further differential gene expression analyses clearly supported the formation of a dormancy phenotype. This study will be helpful for the use of this bacillus as a dormancy model in future studies on TB latency.

Novel gene similar to nitrite reductase (NO forming) plays potentially important role in the latency of tuberculosis

“…Growth is the important characteristic features of the active state of mycobacteria. In our earlier report we have seen that nitrite induces VBNC state by inhibiting the growth of Mtb cells 24 . In order to correlate the effects of varying NO level on the development of non-/replicating status of Mtb bacilli when the growth of KDnirK Mtb strain was measured in presence of nitrite under conditions of w/o antibiotic induction (Fig.…”

“…8 ). The two independent experimental results clearly showed that in ATc induced KDnirK cells grow even in the presence of nitrite (10 mM) whereas the growth was inhibited when the culture is not induced by the antibiotic 24 . This clearly proved that knockdown has successfully been executed on the expression of nirK and the role of the gene is observed in converting nitrite to NO within the cell.…”

“…In addition, there has been no such study done to focus on the nitrite concentration build up at the site of the infected tissue. Interestingly, nitrite has recently been shown as a robust inducer of dormancy in Mtb from in vitro experiments 24 . Also the presence of a significantly high amount of nitrite was observed in collected sputum samples from TB infected patients 25 .…”

Exposure to nitric oxide drives transition to differential culturability inMycobacterium tuberculosis

“…Exposure of mycobacteria to reactive nitrogen species lowers CFU counts [17,28,29], which could indicate the presence of DCB. Mtb incubation with acidified nitrite in 7H9 medium at concentrations above 5 mM reduced Mtb CFU counts, but resuscitation in liquid medium was not achieved (Fig.…”

Effect of Genital Tuberculosis on Ovarian Reserve

“…for the diagnosis of TB. In addition, bacterial plasticity and mechanisms leading to latency result in loss of culturability 44,45. Difficulties in obtaining an adequate tissue biopsy from various affected areas without causing further damage to the female genital tract makes endometrial tissue the most widely used source for bacteriological diagnosis of FGTB 38,41.…”