Recent Developments in the Application of Flow Cytometry to Advance our Understanding of Mycobacteriumtuberculosis Physiology and Pathogenesis

Abstract

The ability of the bacterial pathogen Mycobacterium tuberculosis to adapt and survive within human cells to disseminate to other individuals and cause active disease is poorly understood. Research supports that as M. tuberculosis adapts to stressors encountered in the host, it exhibits variable physiological and metabolic states that are time and niche‐dependent. Challenges associated with effective treatment and eradication of tuberculosis (TB) are in part attributed to our lack of understanding of these different mycobacterial phenotypes. This is mainly due to a lack of suitable tools to effectively identify/detect heterogeneous bacterial populations, which may include small, difficult‐to‐culture subpopulations. Importantly, flow cytometry allows rapid and affordable multiparametric measurements of physical and chemical characteristics of single cells, without the need to preculture cells. Here, we summarize current knowledge of flow cytometry applications that have advanced our understanding of the physiology of M. tuberculosis during TB disease. Specifically, we review how host‐associated stressors influence bacterial characteristics such as metabolic activity, membrane potential, redox status and the mycobacterial cell wall. Further, we highlight that flow cytometry offers unprecedented opportunities for insight into bacterial population heterogeneity, which is increasingly appreciated as an important determinant of disease outcome. © 2020 The Authors. Cytometry Part A published by Wiley Periodicals, Inc. on behalf of International Society for Advancement of Cytometry.

Optimisation of Mycobacterium bovis BCG Fermentation and Storage Survival

“…Cell samples were dual-stained using calcein violet with an acetoxy-methyl ester group (CV-AM; measures metabolic activity) and sytox green (SG; measures cell wall permeability, a proxy for cell death) followed by flow cytometry. Flow cytometry has become a useful technology in understanding the physiology of M. tuberculosis during TB disease, particularly population heterogeneity [27]. This approach has the advantage of capturing information about the metabolic status of the whole population, whereas colony counting is an indirect measure of population death, quantifies only viable bacteria that are culturable on agar, and does not generate information about organisms that are not immediately culturable.…”

Analysis of the relationship between tuberculosis-related mortality and nitrous oxide emission levels in the world with the environmental Kuznets curve method

“…However, like other diseases, early diagnosis is important in tuberculosis [ 16 – 19 ]. For this, it is important to know risk factors and to evaluate environmental factors [ 20 – 22 ]. In some studies on environmental factors, it has been reported that nitric oxide has been successful in the treatment of tuberculosis [ 23 – 25 ].…”

Current and Future Flow Cytometry Applications Contributing to Antimicrobial Resistance Control

“…FCM has significantly improved our understanding of the physiology and pathology of M. tuberculosis in response to drug therapy [ 74 , 75 ]. Fluorogenic probes, such as 4-N, N-dimethylamino-1,8-naphthalimide [ 76 ] or 3-hydroxychromone (3HC) [ 77 ] in combination with microscopy or flow cytometry, enabled the rapid detection of live and dead M. tuberculosis cells in TB patient sputum samples.…”