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H L David

Publications and source records attributed to H L David.

At least 55 records · Page 3Linked to original sources
PubMed1989

Specificity and antigenicity of mycoside G and other glycolipids from Mycobacterium marinum.

The purpose of this work was to examine the immunologic properties of the phenolicglycolipid produced by M. marinum (mycoside G). Cell mass processed with organic solvents yielded a lipid extract containing mycoside G and four other glycolipid fractions (G2 to G5). No mycoside G was found in the Mycobacterium marinum type strain. Neither mycoside G, nor fractions G2, G3 and G4 were immunogenic in the rabbit whereas fraction G5 was very immunogenic. The immune serum raised in the rabbit showed that fraction G5 is species specific since it was consistently detected in all Mycobacterium marinum strains examined so far.

Animals↗
PubMed1989

Serological specificity of Mycobacterium tuberculosis glycolipids.

Six glycolipid fractions can be extracted from lipid crude extracts of Canetti type strains of M. tuberculosis. Among these fractions are two phenolglycolipids. The major component is a triglycosyl phenolphthiocerol dimycocerosate (PGL-Tb 1) and the second is a monoglycosyl diacyl phenolphthiocerol identical to mycoside B of M. bovis. Similar glycolipid compounds can also be found in wild strains of M. tuberculosis recently isolated from tuberculous patients. One of these compounds has been identified as PGL-Tb 1.

Antibodies, Bacterial↗
PubMed1989

Isoenzymes as tools to discriminate various subdivisions in the Mycobacterium fortuitum complex.

Methods for the characterization of catalase, peroxidase, beta-glucosidase, esterase, and beta-lactamase mycobacterial isoenzymes were described. These methods were applied to examine strains of the M. fortuitum complex. M. fortuitum, M. peregrinum, M. chelonae- M. abscessus and an unnamed species had distinct isoenzyme profiles. M. chelonae and M. abscessus could not be satisfactorily differentiated using the described methods.

Catalase↗
PubMed1989

Isoenzymes profiles in slowly-growing and difficult-to-grow mycobacteria.

The cell-free extracts of 13 slowly-growing mycobacteria were run on polyacrilamide gels (Page) and the various protein bands obtained were tested for peroxidase and catalase enzyme activities. The results obtained were compared to those obtained with M. fortuitum and M. chelonae. Based only on a limited numbers of strains employed, it is suggested that these isoenzyme patterns may permit a better separation of "Wood-pigeon" mycobacteria from both M. avium and M. paratuberculosis and also give distinct profiles for other species used. These results further suggest the potential of isoenzymes as taxonomic markers.

Catalase↗
PubMed1988

Mechanisms of pathogenicity in mycobacteria.

The purpose of this article is to review current knowledge about the mechanisms of pathogenicity of mycobacteria. The following aspects of the problem are discussed: chemically-defined compounds implicated in the mechanisms of pathogenicity; location in the cell wall of these compounds and their biological activities; mechanisms of intracellular survival of pathogenic mycobacteria as compared to intracellular killing of non-pathogenic mycobacteria; and pathogenesis of mycobacterial infection. The future prospects in the elucidation of the mechanisms of pathogenicity and their possible application for a better control of mycobacterial diseases are briefly discussed.

Animals↗
PubMed1988

Characterization of distinct layers of the Mycobacterium avium envelope in respect of their composition by fatty acids, proteins, oligosaccharides and antigens.

The distribution of fatty acids, proteins, polysaccharides and antigens in subcellular fractions of Mycobacterium avium is described. Significant qualitative differences in the chemical composition of the various fractions have been used to further characterize the tripartite structure of the cell wall. In the outer dense layer (POL), in addition to previously described complex amphiphatic lipids, new oligosaccharides (lipooligosaccharides?) and a major glycoprotein were located; and it was found that tuberculostearic acid (TSA) esterified the phospholipids of this outerlayer. Judging from the data, it was proposed that the phospholipids formed a basic matrix monolayer in which other compounds of the POL intercalated. It was suggested that in an aqueous environment the hydrophobic ends of the phospholipids oriented to face the mycolic acid residues of the cell wall skeletons (or CWS) to form the 12 nm thick electron transparent layer. The purified CWS contained alpha-, keto-, and dicarboxylic mycolic acids; alanine, glutamic acid and diaminopimelic acid; and arabinose and galactose. Two additional nonidentified amino acids and an unidentified sugar were found in the CWS. Also, in the CWS the fatty acids: palmitic acid (21.8%), oleic acid (4.3%), stearic acid (9.2%) and TSA (4.3%), were detected. The main fatty acids detected in the cytoplasmic membrane (CM) were palmitic (20%), oleic (14.5%) and stearic (8.6%) acids. Mycolic acids and TSA were absent in the CM phospholipids. The major proteins of the CM (86, 40, and 26 Kd proteins) were distinct from the major proteins detected in the cytosol (CYT) fraction (43, 36, and 19 Kd proteins). A 58 Kd protein was present in both the CM and the CYT. The CYT and CM antigens were found absent in surface antigens extracted using sodium dodecyl sulphate (SDS).

Antigens, Bacterial↗
PubMed1988

Further studies on colistin (polymyxin E)-induced cell leakage in mycobacteria: Mg++ efflux in Mycobacterium avium and its effects on drug-susceptibility.

Action of colistin (polymyxin E) was investigated on the opportunistic pathogenic species Mycobacterium avium ATCC 15769 (resistant strain, MIC greater than 100 micrograms/ml). Mycobacterium intracellulare ATCC 13950: a colistin-susceptible strain (MIC 25 micrograms/ml), was used as a parallel control for Mg++ efflux experiments. After the addition of 100 micrograms/ml of colistin to bacteria suspended in a buffer, both loss of viability and Mg++ efflux were followed for one week. Although there was an initial Mg++ efflux in both strains, it soon attained a plateau in case of the resistant strain without any loss of viability until 48 h, whereas in case of the susceptible strain, Mg++ efflux was about 3 times higher than former, a plateau was attained only 24 h after the drug addition, and the loss of viability started only 6 h after the drug addition. Consequently, the loss of viability of M. avium with later incubation times (6 days) was not due to the action of colistin on the cytoplasmic Mg++ efflux solely, but some additional effect was implicated. The drug-susceptibility of extracellularly-growing and intracellularly-growing (in the J-774 macrophage cell line) M. avium to the antibiotics tested could not be potentiated when they were used in combination with 5 micrograms/ml of colistin (maximal obtainable serum level in man) or the polymyxin B nonapeptide (PMBN), nor in the case of bacteria pretreated with these molecules.

Amoxicillin↗
PubMed1988

Antibacterial action of amphipathic derivatives of isoniazid against the Mycobacterium avium complex.

The antibacterial action of amphipathic derivatives of isoniazid (INH) as compared to the parent hydrophilic molecule was determined against the bacteria of the Mycobacterium avium complex (MAC) using a 7H11 agar-dilution method. The results obtained showed a higher activity of 1-isonicotinyl-2-palmitoyl hydrazine and 1-isonicotinyl-2-(12 hydroxy dodecanoyl) hydrazine as compared to INH. However, when one mannose residue was terminally attached to the fatty acid chain of the latter, it lost its anti-MAC activity. 1-isonicotinyl-2-D-galacturonic acid hydrazone (but not hydrazine) also showed increased activity against MAC. Although pristinamycin was shown to bind to M. avium surface lipids, the INH-pristinamycin derivative was not more active than INH alone. These findings are discussed in respect to a proposed mechanism of diffusion across a lipid barrier.

Anti-Bacterial Agents↗
PubMed1987

Studies on clofazimine-resistance in mycobacteria: is the inability to isolate drug-resistance mutants related to its mode of action?

This study showed that clofazimine was not radiomimetic, it was not a mutagenic compound, it was not an inducer of prophage-lambda, and it did not eliminate plasmids from appropriate host bacteria. The drug caused an effective inhibition of the growth of Mycobacterium aurum, and also inhibited the growth cycle of the mycobacteriophage D29. Cross-resistance between clofazimine, streptomycin and rifampicin could not be demonstrated. Drug-resistance mutants towards clofazimine could not be isolated, and it was found that the existing clofazimine-resistant strains of Mycobacterium tuberculosis were rather susceptible organisms requiring clofazimine in their growth medium to maintain their drug-resistance. Ultrastructural studies showed that clofazimine did not act by cell wall lysis, nor did it act on bacterial ribosomes. Higher concentrations of the drug resulted in bacterial plasmolysis. These findings are discussed in the light of its known properties and proposed mode of action.

Clofazimine↗
PubMed1987

Structure of the cell envelope of Mycobacterium avium.

In this report the cell wall of Mycobacterium avium is shown as a triple-layered structure where the outermost layer was stained by the ruthenium red staining for polysaccharides. The outermost layer hindered the diffusion of chemotherapeutic agents across the wall thus causing multiple drug-resistance by exclusion. The concerted electron microscopy and chemical analysis of chloroform-methanol and Triton X-100 extracts indicated that the outer layer was made of diverse amphiphil glycolipids (mycosides C, glycolipids, peptidolipids, phospholipids) that formed a matrix in which proteins were embedded. The examination of a spontaneous rough mutant indicated that mutations blocking the synthesis of one or several of the amphiphils must leave unsubstituted mycolic acid residues, thus causing surface hydrophobicity and roughness. Judging from our data, a model describing the overall cell envelope of M. avium was proposed. From the comparative analysis of M. avium, its spontaneous rough mutant, and its spheroplasts, some of the functions of the outermost layer were disclosed.

Antigens, Bacterial↗
PubMed1987

Colistin (polymyxin E)--induced cell leakage in Mycobacterium aurum.

Addition of 100 micrograms/ml of colistin (polymyxin E) to an actively-growing culture of Mycobacterium aurum caused apparent loss of viability starting after 20 min of drug addition, whereas significant Mg++ efflux was apparent within 5 min of drug addition. Therefore, Mg++ efflux preceded cell death by at least 15 min. These data confirmed earlier reports showing that colistin interacted with the cytoplasmic membrane of mycobacteria.

Cell Membrane↗
PubMed1987

Mycobacterium simiae and Mycobacterium avium-M. intracellulare mixed infection in acquired immune deficiency syndrome.

Acquired immune deficiency syndrome was diagnosed in a 43-year-old man, born and living in Congo. The patient presented a disseminated infection caused by mycobacteria which were recovered from blood, jejunal fluid, and duodenal and rectal biopsies. Identification, according to conventional tests and mycolate profile determination, showed that Mycobacterium avium-M. intracellulare and M. simiae were both involved.

Acquired Immunodeficiency Syndrome↗
PubMed1987

Uptake of selected antibacterial agents in Mycobacterium avium.

The antibacterial action of 64 drugs against Mycobacterium avium ATCC 15769 was screened in Middlebrook 7H9 liquid medium. The most active drugs were ansamycin, rifampicin, clofazimine, and pristinamycin. The antibacterial action of the selected drugs was confirmed by testing clinical isolates on Middlebrook 7H10 agar medium. The antibacterial actions were not related with the hydrophobicities and molecular weights of the drugs. However, all the active drugs were highly hydrophobic molecules of low polarity. These drugs dissolved into the lipids forming the outer layers of the bacterial envelope and they appeared to interact with the surface amphiphils.

Animals↗
PubMed1986

Action of colistin (polymyxin E) on the lytic cycle of the mycobacteriophage D29 in Mycobacterium tuberculosis.

The antibiotic colistin (polymyxin E) inhibited the lytic cycle of the mycobacteriophage D29 in the tubercle bacilli, but not the D29 adsorption. The protein and nucleic acid synthesis in D29-infected bacteria were not affected significantly. The inhibitory activity was reversed by washing off the antibiotic, and by addition of Ca++, but not in media made iso-osmotic by addition of NaCl or sucrose. Transmission electron microscopy revealed an asymmetric to symmetric transition in the staining profile of the cytoplasmic membrane. Though no mature phage particles were ever observed in colistin-treated, D29-infected tubercle bacilli, loosely arranged aggregates resembling phage proheads were occasionally found. Judging from the above data, it was concluded that colistin inhibited D29 lytic cycle by causing molecular displacements in the inner leaflet of the cytoplasmic membrane, and consequently, the binding sites for D29 structural proteins were not available.

Adsorption↗
PubMed1986

Mycolic acid analysis for clinical identification of Mycobacterium avium and related mycobacteria.

We examined the mycolic acid composition of 133 strains belonging to MAIS complex (Mycobacterium avium-M. intracellulare-M. scrofulaceum) and MAIS intermediate strains and the related species M. asiaticum, M. malmoense, M. shimoidei, and M. simiae. The analysis revealed that about 10% of the strains identified as M. avium-M. intracellulare complex by conventional cultural and biochemical tests were in fact M. simiae strains according to their mycolate composition. Of 25 strains previously studied by the International Working Group on Mycobacterial Taxonomy, 2 (MAIS intermediate and M. asiaticum) presented patterns incompatible with the clusters to which they had been assigned. M. malmoense and both M. simiae serovars shared the same pattern with alpha-, alpha'-, and ketomycolates. We describe here the method used to identify the mycolic acid profiles in detail. We found it to be highly reproducible and convenient for use in mycobacterial reference laboratories.

Chromatography, Thin Layer↗
PubMed1985

Antibacterial action of colistin (polymyxin E) against Mycobacterium aurum.

Mycobacterium aurum was susceptible to the antibiotic colistin (polymyxin E),which had an MIC of 5 micrograms/ml and an apparent bactericidal effect at concentrations above 50 micrograms/ml. Treatment of actively growing cells with sublethal concentrations of colistin (15 micrograms/ml) resulted in synchronized cell division once the antibiotic was removed. Under conditions of synchronized cell growth, one cycle of DNA replication lasted 120 min and one cycle of cell division lasted about 180 min. Although the antibiotic treatment during synchronization experiments did not produce apparent changes in the bacterial envelope, it was accompanied by the accumulation of a polysaccharide-like substance in the bacterial cytoplasm which gradually decreased after the removal of antibiotic and by an increase in the number of mesosomes at 3 h after antibiotic removal. This step was closely linked to the doubling time of bacteria. Lethal concentrations of colistin of 50 and 100 micrograms/ml, which caused about 90 and 99% cell death, respectively, produced significant cytoplasmic membrane injuries, patchy appearance of the cell wall outer polysaccharide layer, and little cell lysis. These data indicate that the cytoplasmic membrane is a site of action of colistin and raise a question as to whether an outer bilayer exists in mycobacteria, at least functionally.

Cell Division↗