Influence of Stress and Antibiotic Resistance on Cell-Length Distribution in Mycobacterium tuberculosis Clinical Isolates

Abstract

Mycobacterial cellular variations in growth and division increase heterogeneity in cell length, possibly contributing to cell-to-cell variation in host and antibiotic stress tolerance. This may be one of the factors influencing Mycobacterium tuberculosis persistence to antibiotics. Tuberculosis (TB) is a major public health problem in developing countries, antibiotic persistence, and emergence of antibiotic resistance further complicates this problem. We wanted to investigate the factors influencing cell-length distribution in clinical M. tuberculosis strains. In parallel we examined M. tuberculosis cell-length distribution in a large set of clinical strains (n = 158) from ex vivo sputum samples, in vitro macrophage models, and in vitro cultures. Our aim was to understand the influence of clinically relevant factors such as host stresses, M. tuberculosis lineages, antibiotic resistance, antibiotic concentrations, and disease severity on the cell size distribution in clinical M. tuberculosis strains. Increased cell size and cell-to-cell variation in cell length were associated with bacteria in sputum and infected macrophages rather than liquid culture. Multidrug-resistant (MDR) strains displayed increased cell length heterogeneity compared to sensitive strains in infected macrophages and also during growth under rifampicin (RIF) treatment. Importantly, increased cell length was also associated with pulmonary TB disease severity. Supporting these findings, individual host stresses, such as oxidative stress and iron deficiency, increased cell-length heterogeneity of M. tuberculosis strains. In addition we also observed synergism between host stress and RIF treatment in increasing cell length in MDR-TB strains. This study has identified some clinical factors contributing to cell-length heterogeneity in clinical M. tuberculosis strains. The role of these cellular adaptations to host and antibiotic tolerance needs further investigation.

Altered Mycobacterium tuberculosis Cell Wall Metabolism and Physiology Associated With RpoB Mutation H526D

“…The ability of rpoB mutants to simulate the stringent response may be beneficial for growth and survival in nutrient-limited environments ( Koch et al, 2014 ) and for resistance to antimicrobial peptides ( Gao et al, 2013 ). The synthesis of (p)ppGpp by Rel Mtb during the Mtb stringent response regulates cell size and morphogenesis and therefore, may also play a role in the increased bacillary length observed in the RpoB mutant H526D, which has been previously described in MDR TB clinical isolates ( Vijay et al, 2017 ).…”

Ultrastructural Analysis of Cell Envelope and Accumulation of Lipid Inclusions in Clinical Mycobacterium tuberculosis Isolates from Sputum, Oxidative Stress, and Iron Deficiency

“…The lineages of the selected clinical M. tuberculosis isolates were determined in the previous study ( Vijay et al, 2017 ).…”

“…This understanding is vital for the development of novel therapeutic targets. In our previous study, we have observed that host stresses influenced cell length distribution in a large set ( n = 158) of clinical M. tuberculosis isolates ( Vijay et al, 2017 ). In this study we investigated the accumulation of lipid inclusions and cell envelope ultrastructure of M. tuberculosis in sputum by transmission electron microscopy (TEM).…”

Tolerance and Persistence to Drugs: A Main Challenge in the Fight Against Mycobacterium tuberculosis

“…Interestingly, deletion of lamA in M. tuberculosis leads to the loss of single-cell heterogeneity and faster killing by vancomycin and rifampicin ( Rego et al, 2017 ). Finally, M. tuberculosis cells grown in stressful conditions, such as oxidative stress or iron deficiency, or recovered from sputum or infected macrophages, were shown to have increased cell-size heterogeneity, suggesting that asymmetric cell division might play a role in the variable outcome of treatment of M. tuberculosis ( Vijay et al, 2017b ).…”