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Query: UMLS:C0026918 (Mycobacterium)
 52,428 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We investigated the potential of a rapid colorimetric microassay based on the reduction of dimethylthiazol-diphenyltetrazolium bromide (MTT) for determining the growth of Mycobacterium avium-M. intracellulare complex (MAC) and MICs of clofazimine, resorcinomycin A, and the quinolone PD 127391 against MAC. The reduction of MTT was directly proportional to the number of viable bacteria. A comparison of the MTT reduction test with the [3H]glycerol uptake assay showed the former to possess higher analytical sensitivity for detecting MAC growth in microtiter plates. The MIT reduction test avoids the use of radioisotopes and costly material and equipment; it is reliable, reproducible, and convenient for rapid routine susceptibility testing of MAC.
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PMID:Determination of MICs for Mycobacterium avium-M. intracellulare complex in liquid medium by a colorimetric method. 766 57

Lipoarabinomannan (LAM) is a major antigen of mycobacterial cell walls, involved in host-Mycobacterium interactions. In a previous work, LAM from the vaccine strain, Mycobacterium bovis BCG, was found to exhibit mannooligosaccharides at its arabinan nonreducing ends (ManLAM). The present report concerns the mannan core structure of this ManLAM. After partial hydrolysis of ManLAM, two populations of mannans (Ma1 and Ma2) were obtained by gel filtration chromatography. Their structural features were defined by means of two-dimensional homo- and heteronuclear (1H-13C) NMR sequences and methylation analysis. They were both found to be composed of an alpha-(1-->6)-linked mannan backbone with alpha-(1-->2)-Manp-linked side chains. They are highly branched, and Ma2 presents a higher frequency of branching than Ma1. Moreover, chemical analysis indicates that only Ma1 is phosphorylated. By a two-dimensional heteronuclear 1H-31P total correlation experiment, the phosphate was found to be involved in a phosphodiester bond between inositol C-1 and glycerol C-3. Then, the molecular mass of mannan was established by mass spectrometry, which revealed a molecular mass of 3517 Da for the major molecular species of Ma1. Likewise, analysis of unfractionated mannans showed the occurrence of other, quantitatively minor molecular species, endowed with two phosphates. This study clearly indicates that the mannan region of M. bovis BCG ManLAM exists as a heterogeneous population of molecules whose structures differ in their degree of glycosylation, level of branching, and phosphorylation state. The hypothesis that the relative abundance of these different molecules modulates the biological functions of LAM is discussed.
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PMID:Structural analysis of the mannan region of lipoarabinomannan from Mycobacterium bovis BCG. Heterogeneity in phosphorylation state. 779 82

5-Mycoloyl-beta-arabinofuranosyl-(1-->2)-5-mycoloyl-alpha-ar abinofuranosyl-(1-->1')-glycerol, an antigenic glycolipid from the Mycobacterium avium-intracellulare complex (MAC) was examined for its applicability to the serodiagnosis of MAC infection by ELISA. Serum IgM antibody titres against this glycolipid in healthy controls, pulmonary tuberculosis patients and sputum-MAC-culture-negative MAC patients were generally below the cut-off point (ELISA-negative), whereas most of the MAC-culture-positive MAC patient sera were ELISA-positive (93.5%) and their titres were often very high. Thus, high serum IgM titres against this glycolipid may be said to imply that the MAC disease is in an active phase.
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PMID:Evaluation of the use of 5-mycoloyl-beta-arabinofuranosyl-(1-->2)-5-mycoloyl- alpha-arabinofuranosyl-(1-->1')-glycerol in serodiagnosis of Mycobacterium avium-intracellulare complex infection. 821 Jun 80

A glucuronic acid-containing diacylglycerol was isolated from exponentially growing Mycobacterium smegmatis. Structural analysis of the purified glycolipid, performed by gas chromatography-mass spectrometry, fast atom bombardment-mass spectrometry, and high resolution proton NMR, indicated the structure 3-(O-alpha-D-glucuronopyranosyl)-1,2-diacyl-sn-glycerol. Two forms of the glycolipid were observed differing in fatty acid composition. Both molecular species contained a hexadecanoic acid residue, whereas the second acyl group was either tuberculostearic acid (10-methylstearic acid) or octadecenoic acid. The inherent antigenicity of the glycolipid was shown by its ability to bind to anti-Mycobacterium avium (serovar 26) and anti-Mycobacterium tuberculosis sera by Western blot-type thin-layer chromatography. This is the second instance of the isolation of a glycosyl diacylglycerol from members of the Mycobacterium genus, further confirming its close relationship to Gram-positive bacteria.
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PMID:Isolation and characterization of a novel glucuronosyl diacylglycerol from Mycobacterium smegmatis. 839 36

Tuberculosis has been recently diagnosed in four wild seals found stranded in the Atlantic coast of Argentina. By bacteriological studies and IS6110 hybridization, these isolates were characterized as belonging to the Mycobacterium tuberculosis complex. A genetic characterization using RFLP (Restriction fragment length polymorphism) and a species-specific probe of M. tuberculosis, called mtp40, showed hybridization with this probe on a single band. A similar band was also found in M. tuberculosis H37Rv. This showed a relationship between M. tuberculosis and the wild seal isolates. However these would also seem to belong to a different genetic group in the M. tuberculosis complex, since they do not grow on glycerol-egg containing medium (Lowenstein-Jensen) as typical M. tuberculosis strains usually do. Repeated sequences pMBA2, pTNB12, DR and IS6110 were used as probes to evaluate the epidemiological relationships between the 4 cases of tuberculosis. A low degree of polymorphism was observed, that suggested that these isolates were epidemiologically related.
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PMID:Genetic characterization of mycobacteria from South American wild seals. 860 58

Carboxymycobactin, in which the usual intracellular mycobactin siderophore is modified by possession of a carboxylic acid group, has been isolated as a second extracellular siderophore from culture filtrates of Mycobacterium smegmatis grown under iron-deficient conditions. (The primary siderophore is an exochelin which is a trihydroxamate, pentapeptide derivative). There may be up to 12 similar molecules produced with differing chain lengths that can be recognized by HPLC or HPTLC. The amount of carboxymycobactin is about 20 times higher when cultures are grown with glycerol instead of glucose. Formation is maximal with an initial pH of the medium of about 8.4. The proportion of carboxymycobactin to the total siderophore produced--mainly exochelins--is maximally 10% (usually 10-25 micrograms ml(-1)). Formation of both extracellular siderophores (exochelin and carboxymycobactin) and of the intracellular mycobactin is maximal at the same initial concentration of iron added to the medium, 0.05-0.1 micrograms Fe ml(-1), though exochelin is synthesized 24 h in advance of both carboxymycobactin and mycobactin.
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PMID:The occurrence of carboxymycobactin, the siderophore of pathogenic mycobacteria, as a second extracellular siderophore in Mycobacterium smegmatis. 880 Aug 16

Interfering substances have been reported to inhibit PCR assays for the direct detection of Mycobacterium tuberculosis in clinical specimens. Using an internal control, we determined that 52% of respiratory specimens interfered with our PCR assay. On the basis of these findings, we tried to circumvent the problem by simply diluting prepared sediments. With sediment from a routinely processed sputum known to be inhibitory to PCR, one aliquot was prepared in a routine manner for PCR. Remaining sediment was diluted in phosphate-buffered saline, Middlebrook 7H10 broth, or BACTEC 12B broth; an internal control was added to all reaction mixtures and controls. Internal control was detected only in the sample diluted with BACTEC 12B medium. Components of the BACTEC 12B medium including PANTA reagent (polymyxin B, amphotericin B, nalidixic acid, trimethoprim, and azlocillin), reconstituting fluid, 0.2% glycerol, 0.05% Tween 80, and 0.05% bovine serum albumin (BSA) were tested in a similar manner. Only 0.05% BSA resulted in amplification of the internal control DNA. Varying concentrations of BSA were added to 11 aliquots of a respiratory sediment known to be inhibitory to the PCR. Internal control was detected in all reaction mixtures containing 0.00038 to 0.1% BSA. To determine the ability of BSA to override inhibition, respiratory specimens were run in triplicate: undiluted, diluted 1:2 with BACTEC 12B medium, or diluted with 0.026% BSA. For 21 of 22 inhibitory specimens, BSA was able to override the presence of interfering substances. These data suggest that the presence of BSA in a PCR assay is critical for the direct detection of M. tuberculosis in respiratory specimens.
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PMID:Substances interfering with direct detection of Mycobacterium tuberculosis in clinical specimens by PCR: effects of bovine serum albumin. 886 70

Lipoarabinomannans from fast growing Mycobacterium sp., namely AraLAMs, stimulate the early events of macrophage activation. The immunological activities of all of these AraLAMs drastically decrease with the loss of the mild alkali groups, which were believed to be restricted to the fatty acid residues from the phosphatidyl-myo-inositol anchor. This report reveals the presence and the structure of mild alkali-labile phosphoinositide units linked via the phosphate to the C-5 of the beta-D-Araf in the AraLAMs of Mycobacterium smegmatis, a fast growing mycobacterial species. Their structure was unambiguously established with a strategy based on both one-dimensional 31P and two-dimensional 1H-31P heteronuclear multiple quantum correlation spectroscopy (HMQC) and HMQC-homonuclear Hartmann-Hahn spectroscopy NMR experiments applied to native AraLAMs and to AraLAMs treated in mild alkali conditions. Next to these alkali-labile phosphoinositides estimated at three per molecule, two other mild alkali-stable phosphoinositide units were identified: the expected (myo-inositol-1)-phosphate-(3-glycerol) unit typifying the well known glycosylphosphatidylinositol anchor of the mannan core and, more surprisingly, one (myo-inositol-1)-phosphate-(5-beta-D-Araf) unit having the same structure as the alkali-labile ones. Moreover, these four phosphoinositide units were found capping the arabinan side chains. Thus, their different behavior toward mild alkaline hydrolysis was explained according to their accessibility to the alkali reagent. This novel class of LAMs, namely phosphoinositols-glyceroarabinomannans (PI-GAMs), are characterized by their phosphoinositide units but also by the absence of fatty acid residues. These PI-GAMs were found to elicit the secretion of tumor necrosis factor-alpha, suggesting that phosphoinositides are the major PI-GAM epitope involved in this process.
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PMID:Mycobacterium smegmatis phosphoinositols-glyceroarabinomannans. Structure and localization of alkali-labile and alkali-stable phosphoinositides. 899 36

Two glycerol utilization mutants of Mycobacterium smegmatis that were unable to utilize most carbon sources except glucose were isolated. Supplementation of these media with small amounts of glucose restored growth in the mutants; these strains are therefore glucose auxotrophs. The mutant phenotype is complemented by the gene encoding phosphoglucose isomerase (pgi), and direct measurement of enzyme activities in the mutants suggests that this gene product is absent in the auxotrophic strains. Mapping of the mutant allele by Southern analysis demonstrates the presence of a 1-kb deletion extending into the coding sequence of pgi. The possible roles of phosphoglucose isomerase in mycobacterial cell wall synthesis and metabolic regulation are discussed.
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PMID:Interruption of the phosphoglucose isomerase gene results in glucose auxotrophy in Mycobacterium smegmatis. 909 72

Aspergillus nidulans conidiospores contain high levels of the non-reducing disaccharide trehalose. We show that upon induction of conidiospore germination, the trehalose pool is rapidly degraded and a glycerol pool is transiently accumulated. A trehalase with an acidic pH optimum was purified from conidiospores. Characterization of the treA gene encoding this trehalase shows that it is homologous to Saccharomyces cerevisiae vacuolar acid trehalase, the product of the ATH1 gene, and to two related proteins of unknown function identified in Mycobacterium tuberculosis and Mycobacterium leprae. A. nidulans mutants that lack acid trehalase activity were constructed by gene replacement at the treA locus. Analysis of these mutants suggests that the treA gene product is localized in the conidiospore wall, is required for growth on trehalose as a carbon source, and is not involved in the mobilization of the intracellular pool of trehalose. Therefore, it is proposed that a cytoplasmic regulatory trehalase is controlling this latter process.
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PMID:Molecular characterization of the Aspergillus nidulans treA gene encoding an acid trehalase required for growth on trehalose. 914 Sep 77


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