The mode of antibacterial action of the novel agent ZM240304 (D-arabino-2,3,4-tris(4-chlorobenzyl) pentane-1,5-diamine).

ZM240304 is an example of a new class of antibacterial agents that is active against experimental infections in animals. The compound was demonstrated to be a membrane-active compound that disrupted the outer membrane of Gram-negative organisms and allowed the leakage of periplasmic enzymes. Respiration was inhibited and cellular ATP levels were reduced, leading to cell death.

Ergosterol biosynthesis inhibition: a target for antifungal agents.

The isoprenoid sterols play a crucial role in the viability of all fungi; those unable to synthesise ergosterol because of inhibition, growth conditions or mutation must take it up from the environment. A range of compound types have been discovered which interfere with the biosynthetic pathway from acetate to ergosterol and these compounds have antifungal actions. Inhibition of several of the steps has yielded agents which have been used with great success as medical and agrochemical agents.

A comparison of the accumulation of novobiocin into bacteria with its antibacterial properties.

The accumulation of novobiocin in bacteria has been compared with the MIC, inhibition of DNA biosynthesis and inhibition of the activity of isolated DNA gyrase for a range of species. There was a good correlation between MIC and the inhibition of DNA biosynthesis and DNA gyrase. Novobiocin accumulation did not correlate with any other parameter.

The membrane destabilising action of the antibacterial agent chlorhexidine.

The antibacterial agent chlorhexidine has long been used as an agent for medical antisepsis. This compound is a membrane active agent which probably has its major antibacterial action by interference with the function of cellular membranes. The results demonstrated an inhibition of oxygen utilisation by bacteria which was related to falls in cellular ATP levels.

The accumulation of novobiocin by Escherichia coli and Staphylococcus aureus.

The accumulation of novobiocin by Escherichia coli was shown to be a nonsaturable process. Inhibitors or uncouplers of respiration had no effect on accumulation in cells grown in Isosensitest broth, whereas, bacteria grown in nutrient broth demonstrated an energy-dependent efflux mechanism. In contrast, accumulation of novobiocin by Staphylococcus aureus was found to have a Km of 74 microM and uncouplers and inhibitors of respiration reduced the accumulation suggesting that in S.

(6S)-6-fluoroshikimic acid, an antibacterial agent acting on the aromatic biosynthetic pathway.

(6S)-6-Fluoroshikimic acid inhibited the growth of Escherichia coli B on minimal medium (MIC, 0.25 micrograms ml-1), and it protected mice challenged intraperitoneally with the same organism (50% protective dose, 0.06 mg kg of body weight-1).

Biochemical changes associated with the antifungal action of the triazole ICI 153,066 on Candida albicans and Trichophyton quinckeanum.

The triazole antifungal agent, ICI 153,066, acts on Candida albicans and Trichophyton quinckeanum by inhibiting demethylation of the sterol ring. In C. albicans this is at the level of lanosterol whereas in T.

Evaluation of the dipeptide and oligopeptide permeases of Candida albicans as uptake routes for synthetic anticandidal agents.

In order to obtain information essential for the design of synthetic anticandidal drugs that can exploit peptide permeases to gain access to intracellular targets, the substrate specificities of the dipeptide permease (Dpp) and oligopeptide permease (Opp) of Candida albicans have been studied. The permeases show strict stereospecificity, a preference for large, hydrophobic and N-terminal Ala residues, and marked discrimination against basic and acidic side chain residues. Comparison of results from several transport assays indicated that measuring loss of peptide substrate from the medium using fluorescence labelling procedures gave reliable transport rates and kinetic parameters, whereas in contrast, measuring accumulation of radioactivity from labelled substrates gave erroneous results arising from substrate metabolism and exodus.

Peptide substrates rapidly modulate expression of dipeptide and oligopeptide permeases in Candida albicans.

Previous studies showed that peptide transport activity in Candida albicans was completely repressed by NH4+, and that growth on amino acids as sole nitrogen source stimulated transport to a basal level. Here we show that addition of peptide mixtures to culture media gives a further 5-fold increase in transport of dipeptides and oligopeptides; the effect is specific for peptide transport, amino acid uptake being unaffected. Presence of peptides but not amino acids overrides NH4+ repression of peptide transport.

The lipid composition and permeability to the triazole antifungal antibiotic ICI 153066 of serum-grown mycelial cultures of Candida albicans.

The total lipid content of Candida albicans (serotype A: NCPF 3153) exponential-phase mycelial cultures grown in tissue-culture medium 199 (containing 10%, v/v, foetal calf serum) was 29.8 +/- 8 mg (g dry weight)-1 (mean +/- SD). The weight ratios of phospholipid to neutral lipid and phospholipid to non-esterified sterol were 2.

Inhibition of 14 alpha-sterol demethylase activity in Candida albicans Darlington does not correlate with resistance to azole.

The 14 alpha-sterol demethylase in the azole-resistant Candida albicans, strain Darlington, is less sensitive to the triazole ICI 153066 than are two azole-sensitive strains, A and B. However, there is no direct correlation between the IC50 values for triazole inhibition of the demethylase and IC50 values for growth. It appears that the basis of azole resistance in strain Darlington may not be explained solely on the basis of a lack of sensitivity of its 14 alpha-sterol demethylase enzyme, but that other target sites for azole may be altered or absent.

The lipid composition and permeability to azole of an azole- and polyene-resistant mutant of Candida albicans.

Candida albicans 6.4, which is resistant to both polyene and azole groups of antifungal antibiotics, has a larger lipid content and lower polar lipid to neutral lipid ratio compared with other strains that are sensitive or resistant only to azoles. C.

Sterols in Candida albicans mutants resistant to polyene or azole antifungals, and of a double mutant C. albicans 6.4.

Investigations of resistant mutants could help resolve differences and similarities in the action of azole and polyene antifungals whose modes of action are related; both disrupt membrane properties, such as permeability, by interfering with membrane sterols--polyenes by direct binding and azoles by inhibiting their synthesis. Studies of laboratory-derived mutants of Candida albicans which have an altered sterol content and/or an altered sterol composition do not provide evidence for a unified mechanism of polyene resistance. Clinical isolates of azole-resistant C.

The lipid composition of azole-sensitive and azole-resistant strains of Candida albicans.

The lipid compositions of two azole-sensitive (A and B2630) and two azole-resistant (AD and KB) strains of the opportunistic fungal pathogen Candida albicans were studied by using several lipid extraction procedures: no differences were observed between the lipid content or total phospholipid/neutral lipid ratios of the four strains. All contained phosphatidylethanolamine, phosphatidylcholine, phosphatidylinositol and phosphatidylserine as major phospholipids, with smaller amounts of phosphatidylglycerol and diphosphatidylglycerol; the relative proportions of these lipids differed between all four strains. The fatty acid composition of each major phospholipid within each strain differed, and there were also interstrain differences.

The mode of antifungal action of tolnaftate.

The anti-dermatophyte agent tolnaftate was compared with the allylamine antifungal compounds naftifine and terbinafine. Tolnaftate was shown to inhibit sterol biosynthesis at the level of squalene epoxidation and squalene was shown to accumulate in dermatophytes grown in its presence. Biochemical studies in whole and broken cells supported this conclusion and showed that the compound was active against squalene epoxidation in broken C.

A new mucotropic agent--in vitro and in vivo evaluation of 2-alpha-thenoylthiopropionylglycine (bronchoplus).

A new mucotropic agent, 2-alpha-thenoylthiopropionylglycine (TTPG) has been evaluated using two in vitro mucus models (pig gastric mucin and human bronchial mucus) and an in vivo model, the oral administration for a period of 7 days to a mini-pig fitted with a tracheal-pouch. TTPG at 2% concentration caused a 40% reduction in the viscosity of mucus gels in vitro, as compared to a control with water. Tracheal mucus samples collected from the pouch were examined rheologically and biochemically.

A comparison of phospholipase activity, cellular adherence and pathogenicity of yeasts.

Phospholipase A and lysophospholipase activities were measured in the culture fluid and in the blastospores of Candida albicans. When phospholipase activity was measured in six yeasts (four strains of C. albicans and a single strain each of Candida parapsilosis and Saccharomyces cerevisiae) a correlation was found between this activity and two potential parameters of pathogenicity.

The detection and analysis of chitinase activity from the yeast form of Candida albicans.

Chitinase activity was detected in the supernatant fraction of a high-speed centrifugation preparation of broken Candida albicans yeast cells. The enzyme showed peak activity during the rapid budding phase of growth and was found to parallel the chitin synthase activity. The optimum conditions for the hydrolysis of chitin, regenerated from acetylation of chitosan, were determined.

Azole resistance in Candida albicans.

Two isolates of Candida albicans from chronic mucocutaneous candidosis patients who initially responded to ketoconazole treatment but who later relapsed, have shown an abnormal response to ketoconazole in four out of five systems in vitro and in three animal models of vaginal or systemic infection. They have also shown abnormal resistance to inhibition of ergosterol biosynthesis in whole cells, but not in cell-free systems, and to inhibition of amino acid uptake. We conclude that the behaviour of the isolates is consistent with the development of drug resistance to ketoconazole.

The use of natural-abundance high-resolution carbon-13 NMR in the study of mucus glycoproteins.

Natural-abundance 13C NMR was used to study samples of native mucus from dog trachea and purified mucus glycoprotein from hog stomach. Despite the large molecular weight of the molecules (several million) and visco-elastic nature of the gel, spectra were produced which could be resolved into individual sharp resonances which gave significant structural detail. These results indicate the potential use of this powerful technique in the study of mucus glycoprotein structure in the undegraded molecule.

Isolation and partial characterization of a rheologically active glycoprotein fraction from pooled human sputum.

A rheologically active mucin fraction was isolated from pooled sputum and was shown to be free of any major protein contaminants. The procedure used allows the isolation to be carried out by a batch process so that sufficient material is available for extensive biochemical and biophysical studies. Because the separation was carried out using sputum, the purified material should prove suitable for the evaluation of drugs used in chronic obstructive airway disease.