Effects of clofazimine on potassium uptake by a Trk-deletion mutant of Mycobacterium tuberculosis.

Objectives: This study was designed to investigate the effects of the membrane-active, anti-mycobacterial agent, clofazimine, on potassium (K+)-uptake by a mutant of Mycobacterium tuberculosis (MTB), in which the Trk system, the major K+ transporter of this microbial pathogen, had been selectively inactivated.

Methods: The ceoB and ceoC genes of MTB, which encode the TrkA proteins, CeoB and CeoC, were deleted by homologous recombination, and the double-knockout mutant and wild-type strains compared with respect to K+ uptake and growth in the presence and absence of clofazimine (0.015-2.

Antimicrobial activity of clofazimine is not dependent on mycobacterial C-type phospholipases.

We have used a phospholipase C (PLC)-deletion mutant (plcABC) of the H37Rv strain of Mycobacterium tuberculosis (MTB), as well as a plcA-insertion mutant of Mycobacterium smegmatis, to investigate the possible involvement of PLCs in clofazimine-mediated inhibition of mycobacterial K(+) transport and growth. Inactivation of the PLCs of MTB and insertion of the plcA gene into M. smegmatis resulted in a substantial reduction and increase in hydrolysis of phosphatidylcholine (PC), respectively.

Proinflammatory interactions of pneumolysin with human neutrophils.

The effects of pneumolysin on the proinflammatory activity of human neutrophils, as well as on cation fluxes in these cells, have been investigated. Superoxide production, release of elastase, CR3 expression, phospholipase A2 activity, and alterations in membrane potential were measured by use of lucigenin-enhanced chemiluminescence and colorimetric, flow cytometric, radiometric, and spectrofluorimetric procedures, respectively; and cation fluxes were measured by use of 45Ca2+ and 86Rb+ and by fura-2 spectrofluorometry. Pneumolysin at concentrations >1.

Antimycobacterial action of B4128, a novel tetramethylpiperidyl-substituted phenazine.

The effects of the novel tetramethylpiperidyl (TMP)-substituted phenazine, B4128 (0.6-2.5 mg/L), on growth, phospholipase A2(PLA2) activity, cation (K+, Ca2+) fluxes and energy metabolism (ATP) of Mycobacterium aurum A(+) and Mycobacterium tuberculosis (H37Ra) have been investigated in vitro.

In vitro investigation of the antimicrobial activities of novel tetramethylpiperidine-substituted phenazines against Mycobacterium tuberculosis.

The intra- and extracellular activities of 5 novel tetramethylpiperidine (TMP)-substituted phenazines against Mycobacterium tuberculosis H37Rv (ATCC 27294) were determined and compared with those of clofazimine and rifampicin. Two of these agents, together with clofazimine, were also tested for their activities against drug-resistant strains of M. tuberculosis.