The in vitro and in vivo anti-mycobacterial activities of a number of phenothiazine compounds are reviewed. These compounds, normally employed for the management of psychosis, inhibit the growth in vitro of Mycobacterium tuberculosis at concentrations that are significantly greater than those that can safely be achieved in a patient harbouring these infections. Nevertheless, one of these phenothiazines, chlorpromazine, is concentrated by human macrophages to 10-100 times its concentration in plasma, and has activity against mycobacteria that have been phagocytosed by these cells. Phenothiazines have significant in vitro activity against susceptible, polydrug- and multidrug-resistant strains of M. tuberculosis, as well as enhancing the activity of some agents employed for first-line treatment. Because thioridazine, the very mild anti-psychotic agent whose most common side effect is drowsiness, has equal anti-tuberculosis properties in vitro to chlorpromazine, we recommend that thioridazine be studied as an adjuvant to the four- or five-drug regimens employed for the management of a freshly diagnosed tuberculosis infection of unknown antibiotic susceptibility, at least during the period required for the assessment of antibiotic susceptibility. Because it also enhances the activity of rifampicin and streptomycin, antibiotics that frequently have adverse effects, additional studies evaluating the use of thioridazine as an adjuvant may eventually allow a reduction in the dosages of these antibiotics and result in a decreased frequency of adverse effects. It is important to note that whereas the management of patients with thioridazine for periods in excess of many months will result in the appearance of some undesirable side effects, its use for a limited period of 2-3 months should not produce side effects that are more severe than simple drowsiness. Nevertheless, further in vitro and in vivo studies are essential before thioridazine may be recommended for the management of select cases of pulmonary tuberculosis.

Activity of phenothiazines against antibiotic-resistant Mycobacterium tuberculosis: a review supporting further studies that may elucidate the potential use of thioridazine as anti-tuberculosis therapy

Enhancement of antibiotic activity against poly-drug resistant Mycobacterium tuberculosis by phenothiazines.

Phenothiazines have been shown to inhibit the in vitro growth of multi-drug resistant (resistant to rifampicin and isoniazid) Mycobacterium tuberculosis (MDRTB). They have been considered as potential adjuvants to regimens employing four or more antibiotics for the management of freshly diagnosed infections of M. tuberculosis in patients from areas known to have a high prevalence of MDRTB. Chlorpromazine has been shown to enhance the activity of antibiotics (except ethambutol) to which M. tuberculosis is susceptible. This might result in a reduction in the dose of some or all of the antibiotics employed without sacrificing the integrity of treatment. Chlorpromazine, thioridazine and promethazine were shown to enhance the activity of rifampicin and streptomycin when used in combinations at concentrations that are minimally effective when employed separately against clinical strains of M. tuberculosis resistant to two or more antibiotics (poly-drug resistant MTB). The phenothiazines had no effect on the activity of isoniazid against poly-drug resistant MTB. © 2001 Elsevier Science B.V. and International Society of Chemotherapy All rights reserved.

Short communication Enhancement of antibiotic activity against poly-drug resistant Mycobacterium tuberculosis by phenothiazines

Publisher Summary This chapter describes the recent advances and hypotheses concerning the role of Ca2+ in prokaryotes, and begins with the propositions—namely, (1) because calcium was present during the early stages of the evolution of life, all cells might be expected to be able to guard against the toxic effects of Ca2+ and; (2) the roles that Ca2+ came to play in the early cells may have been conserved during subsequent evolution Escherichia coli (E coli) has been shown to maintain a low free intracellular Ca2+ concentration, similar to that found in eukaryotic cells, against large changes in external Ca2+ concentrations The metabolic apparatus that serves this function involves Ca2+ channels, Ca2+ antiporters, and ATP-dependent Ca2+ pumps, together with intracellular, Ca2+ -binding buffers such as the S erythraea protein, calerythrin Along with other divalent cations, Ca2+ clearly plays a structural role in prokaryotic cell walls Less defined, in eukaryotes as well as prokaryotes, are the interactions between Ca2+ and cell membranes Ca2+ can play a role in regulating lipid synthesis and consequently membrane composition It has been indicated that Ca2+ is involved in nucleoid structure and the function of proteins required for DNA replication contributes to the concept The investigations of putative calmodulin-like and other Ca2+ binding proteins in prokaryotes have demonstrated that proteins are present that are able to activate calmodulin-dependent proteins The approach adopted for the identification of Ca2+ “associated” proteins in E coli serves to provide a better understanding of the relevance of Ca2+ binding proteins in bacteria

Calcium and bacteria.

Comparative in vitro activity of phenothiazines against multidrug-resistant Mycobacterium tuberculosis.

In Mycobacterium phlei TMC 1548 supplementation of growth medium containing 2% v/v glycerol with glucose(up to 5% w/v) resulted in an increase in growth (yield of cells), in amount of total phospholipids, and in each of the individual phospholipids (cardiolipin, phosphatidylethanolamine, phosphatidylinositol and its mannosides, and phosphatidylglycerol) However, when the medium was supplemented with a higher concentration (75% w/v) of glucose, both growth and phospholipid levels decreased to near control values (2% v/v glycerol alone) Cyclic AMP levels, which decreased at all concentrations of glucose, had no relation to phospholipid content or growth The presence of a protein that possesses the property of stimulating c-AMP phosphodiesterase activity was recently demonstrated in Mycobacterium smegmatis (Falah et al 1988 FEMS Microbiol Lett 56: 89–93) In M phlei the level of this calmodulin-like protein (assayed by radioimmunoassay) changed with different concentrations of glucose in the growth 

Correlation between calmodulin-like protein, phospholipids, and growth inglucose-grown Mycobacterium phlei

When Mycobacterium smegmatis TMC1546 was grown at different concentrations of glucose supplemented to a synthetic medium already containing 2% v/v glycerol, the following changes were observed. Amount of calmodulin-like protein (CAMLP), total and individual phospholipids (PLs) namely phosphatidylethanolamine, cardiolipin, phosphatidylglycerol and phosphatidylinositol mannosides and total lipids and growth increased up to 5% w/v but decreased at higher concentrations of glucose (7.5% w/v and above). Cyclic AMP content of the whole cells decreased continuously with increase in glucose concentration in the medium. Incorporation of 32Pi into total phospholipids was inhibited by two calmodulin antagonists trifluoperazine and phenothiazine (50% at 40 μM) and the calcium-specific chelator ethylene glycol bis (β-aminoethyl ether) N,N,N′,N′-tetraacetate (EGTA) 35% at 2 mM. Total lipids, CAMLP and growth of this organism are also modulated in a similar way in response to the glucose concentration in the growth medium. Taking these observations together it is suggested that CAMLP has some effect on the metabolism of PLs.

P. Hemalata Reddy

Papers

Correlation between calmodulin-like protein, phospholipids, and growth inglucose-grown Mycobacterium phlei

Calmodulin-like protein and the phospholipids of Mycobacterium smegmatis.