Loss of circulating CD8α NK cells during human infection.

Natural Killer (NK) cells can recognize and kill -infected cells in vitro, however their role after natural human exposure has not been well-studied. To identify -responsive NK cell populations, we analyzed the peripheral blood of healthy household contacts of active Tuberculosis (TB) cases and source community donors in an endemic region of Port-au-Prince, Haiti by flow cytometry. We observed higher CD8α expression on NK cells in putative resistors (IGRA- contacts) with a progressive loss of these circulating cells during household-associated latent infection and disease.

T cells target TB.

Recently in Nature Medicine, Musvosvi et al. analyzed single-cell T cell receptor (TCR) sequencing by grouping of lymphocyte interactions by paratope hotspots (GLIPH2) in a South African longitudinal cohort at high risk for tuberculosis. They find peptide antigen-specific T cells correlating with control of primary infection, potentially informing future vaccines.

Complete identity and expression of StfZ, the -antisense RNA to the mRNA of the cell division gene , in .

Bacteria regulate FtsZ protein levels through transcriptional and translational mechanisms for proper cell division. A -antisense RNA, StfZ, produced from the intergenic region, was proposed to regulate FtsZ level in . However, its structural identity remained unknown.

Growth and division mechanisms by which genetic resisters emerge from the rifampicin-surviving population of differentially antibiotic-susceptible mycobacterial subpopulations.

Background: We recently reported the de novo emergence of unusually high numbers of antibiotic resisters from the in vitro cultures of Mycobacterium tuberculosis and Mycobacterium smegmatis surviving in the presence of minimum bactericidal concentration (MBC) of antituberculosis antibiotics. The resisters emerged due to multiple asymmetric divisions of elongated mother cells containing multiple nucleoids and multiple septae. We had earlier found a minor subpopulation of short-sized cells (SCs) and a major subpopulation of normal-sized cells (NCs) (10% and 90%, respectively, of the whole population), with significant difference in antibiotic susceptibility and resister generation frequency, in the in vitro cultures of M.

Deletion of rifampicin-inactivating mono-ADP-ribosyl transferase gene of globally altered gene expression profile that favoured increase in ROS levels and thereby antibiotic resister generation.

The physiological role of mono-ADP-ribosyl transferase (Arr) of , which inactivates rifampicin, remains unclear. An earlier study reported increased expression of during oxidative stress and DNA damage. This suggested a role for Arr in the oxidative status of the cell and its associated effect on DNA damage.

Elevated Levels of Three Reactive Oxygen Species and Fe(II) in the Antibiotic-Surviving Population of Mycobacteria Facilitate Emergence of Genetic Resisters to Antibiotics.

We had earlier reported the emergence of genetic resisters of Mycobacterium tuberculosis and Mycobacterium smegmatis to rifampicin and moxifloxacin from the antibiotic-surviving population containing elevated levels of the non-DNA-specific mutagenic reactive oxygen species (ROS) hydroxyl radical. Since hydroxyl radical is generated by Fenton reaction between Fe(II) and HO, which is produced by superoxide dismutation, we here report significantly elevated levels of these three ROS and Fe(II) in the M. smegmatis rifampicin-surviving population.

A method for the enrichment, isolation and validation of Mycobacterium smegmatis population surviving in the presence of bactericidal concentrations of rifampicin and moxifloxacin.

The bacterial populations surviving in the presence of antibiotics contain cells that have gained genetic resistance, phenotypic resistance and tolerance to antibiotics. Isolation of live bacterial population, surviving against antibiotics, from the milieu of high proportions of dead/damaged cells will facilitate the study of the cellular/molecular processes used by them for survival. Here we present a Percoll gradient centrifugation based method for the isolation of enriched population of Mycobacterium smegmatis surviving in the presence of bactericidal concentrations of rifampicin and moxifloxacin.

Mycobacterial Populations Partly Change the Proportions of the Cells Undergoing Asymmetric/Symmetric Divisions in Response to Glycerol Levels in Growth Medium.

Twenty to thirty percent of the septating mycobacterial cells of the mid-log phase population showed highly deviated asymmetric constriction during division (ACD), while the remaining underwent symmetric constriction during division (SCD). The ACD produced short-sized cells (SCs) and normal/long-sized cells (NCs) as the sister-daughter cells, but with significant differential susceptibility to antibiotic/oxidative/nitrite stress. Here we report that, at 0.

Unique Mode of Cell Division by the Mycobacterial Genetic Resister Clones Emerging from the Antibiotic-Surviving Population.

The emergence of antibiotic genetic resisters of pathogenic bacteria poses a major public health challenge. The mechanism by which bacterial antibiotic genetic resister clones formed multiply and establish a resister population remained unknown. Here, we delineated the unique mode of cell division of the antibiotic genetic resisters of and formed from the population surviving in the presence of bactericidal concentrations of rifampicin or moxifloxacin.

moxifloxacin persister cells produce high levels of hydroxyl radical, generating genetic resisters selectable not only with moxifloxacin, but also with ethambutol and isoniazid.

Bacterial antibiotic persister cells tolerate lethal concentrations of antibiotics but emerge as the antibiotic-sensitive population upon antibiotics withdrawal. However, the possibility of antibiotic-resistant genetic mutants emerging from the antibiotic persister population in the continued exposure to microbicidal concentrations of antibiotics needed investigation. We explored this possibility using the fast-growing as a model organism for biology, as it is known to incur antibiotic-resistant mutations identical to and at identical target positions as found in the clinical isolates of .

Mycobacterial Cultures Contain Cell Size and Density Specific Sub-populations of Cells with Significant Differential Susceptibility to Antibiotics, Oxidative and Nitrite Stress.

The present study shows the existence of two specific sub-populations of and cells differing in size and density, in the id-og hase (MLP) cultures, with significant differential susceptibility to antibiotic, oxidative, and nitrite stress. One of these sub-populations (~10% of the total population), contained hort-sized ells (SCs) generated through highly-deviated asymmetric cell division (ACD) of normal/long-sized mother cells and symmetric cell divisions (SCD) of short-sized mother cells. The other sub-population (~90% of the total population) contained ormal/long-sized ells (NCs).

De Novo Emergence of Genetically Resistant Mutants of Mycobacterium tuberculosis from the Persistence Phase Cells Formed against Antituberculosis Drugs In Vitro.

Bacterial persisters are a subpopulation of cells that can tolerate lethal concentrations of antibiotics. However, the possibility of the emergence of genetically resistant mutants from antibiotic persister cell populations, upon continued exposure to lethal concentrations of antibiotics, remained unexplored. In the present study, we found that Mycobacterium tuberculosis cells exposed continuously to lethal concentrations of rifampin (RIF) or moxifloxacin (MXF) for prolonged durations showed killing, RIF/MXF persistence, and regrowth phases.