New variants of polar glycopeptidolipids detected in Mycobacterium simiae, including 'habana' strains, as evidenced by electrospray ionization-ion trap-mass spectrometry

AIMS

To determine the composition of polar glycopeptidolipids (pGPLs) of Mycobacterium simiae and, particularly, those of 'habana' strains, in a search for specific markers given the immunogenic potential of 'habana' TMC 5135 in experimental tuberculosis.

METHODS AND RESULTS

pGPLs were determined in free lipid extracts using electrospray ionization-ion trap-mass spectrometry (ESI-IT-MS), working in both negative- and positive-ion mode. In the case of TMC 5135, the presence of the previously characterized GPL-II (containing 2,4-di-O-CH(3) glucuronic acid as distal sugar in the oligosaccharide antigenic moiety) and GPL-III (containing 4-O-CH(3) glucuronic acid as distal sugar) was confirmed using MS/MS and MS/MS/MS approaches. Interestingly, some 'habana' strains presented variants of GPL-II, designated GPL-II'-A and GPL-II'-B. A di-O-CH(3)-deoxy-hexose (tentatively, 2,3-di-O-CH(3)-fucose) was identified as the penultimate sugar in the oligosaccharide moiety of GPL-II'-A, whereas in GPL-II'-B the penultimate sugar was fucose (tentative identification). On the contrary, the distal sugar of the oligosaccharide chain of pGPLs of Myco. simiae ATCC 25275(T) was identified as tri-O-CH(3)-glucuronic acid (designated GPL-sim(T)-I, with two variants: GPL-sim(T)-I-A and GPL-sim(T)-I-B), O-CH(3)-glucuronic acid (designated GPL-sim(T)-II) and di-O-CH(3)-glucuronic acid (GPL-II'-A and GPL-II'-B). The penultimate sugar of the oligosaccharide chain of GPL-sim(T)-I-A and GPL-sim(T)-II was identified as di-O-CH(3)-deoxy-hexose (tentatively, 2,3-di-O-CH(3) fucose), and that of GPL-sim(T)-I-B as deoxy-hexose (tentatively, fucose). In all strains studied, each [M-H](-) and [M+Na](+) ion was revealed as a mixture of homologous compounds varying in the number of -O-CH(3) groups present in the oligosaccharide moiety and in the length of the fatty acyl linked to the peptide.

CONCLUSIONS

The present work indicates that, within a similar general pattern of pGPLs, different strains of Myco. simiae present some variations, so that new compounds (GPL-II'-A, GPL-II'-B, GPL-sim(T)-I-A, GPL-sim(T)-I-B and GPL-sim(T)-II) were defined. Noteworthy was the fact that the 'habana' strains clearly differed from the type strain of Myco. simiae.

SIGNIFICANCE AND IMPACT OF THE STUDY

The data obtained can be used in the delineation of the 'habana' group of Myco. simiae, including the quality control of the immunogenic strain 'habana' TMC 5135.

Lipids of ‘Mycobacterium habana’, a synonym of Mycobacterium simiae with vaccine potential

'Mycobacterium habana' was proposed as a distinct species within the genus Mycobacterium; however, it is actually a synonym of Mycobacterium simiae and included in the serotype I of this species. The potential use of 'M. habana' as a vaccine in both leprosy and tuberculosis has led to the analysis of its lipid composition in an attempt to define distinctive markers that could be used in the quality control of true strains of this bacterium. Lipids of taxonomic value (fatty and mycolic acids) are similar in 'M. habana' and M. simiae; nevertheless, they clearly differ on the basis of glycopeptidolipid (GPL) composition. Thus, contrary to M. simiae, most strains of 'M. habana' can be defined by the presence of three polar compounds, designated GPL-I, GPL-II and GPL-III, easily determined by thin-layer chromatography, and characterized, respectively, by the content of l-fucose, 2,4-di-O-Me-d-glucuronic acid, and 4-O-Me-d-glucuronic acid, as epitopes.

Biochemical, antimicrobial susceptibility and genotyping studies on Corynebacterium urealyticum isolates from diverse sources

Thirty-two isolates of Corynebacterium urealyticum, isolated between 1991 and 1995, were studied by biochemical tests, phospholipid content, analysis of fatty and mycolic acids, ribotyping, whole-cell protein patterns and antimicrobial susceptibility to six antibiotics. Nineteen isolates were from human and human-related sources (HHRS); the remainder were from animal and animal-related sources (AARS). Most C. urealyticum isolates were similar in their biochemical and whole-cell protein profiles, although most HHRS isolates were alkaline phosphatase-positive (84%) and produced almost identical protein patterns, whereas AARS isolates were quite diverse. The qualitative composition of cellular fatty acids was identical for all isolates examined. Twelve different ribotypes were obtained with HindIII producing four-to-seven bands. Ribotypes 8, 9 and 10 were predominant in isolates from HHRS, whereas in isolates from AARS, ribotypes 5 and 6 predominated. AARS isolates were significantly less antibiotic-resistant, in comparison with HHRS isolates. Ribotyping appeared to be the most useful tool for strain characterisation.

Detection of mycoloylglycerol by thin-layer chromatography as a tool for the rapid inclusion of corynebacteria of clinical origin in the genus Corynebacterium

A chemotaxonomic study of some corynebacteria isolated from clinical samples revealed characteristic thin-layer chromatographic patterns for meso-diaminopimelic acid containing species included in the genera Corynebacterium, Dermabacter and Brevibacterium. Notably, a specific compound was consistently detected in mycolic acid containing species of the genus Corynebacterium. This compound was composed by glycerol and mycolic acids and structural analyses carried out by fast atom bombardment mass spectrometry in C. minutissimum confirmed its identification as mycoloylglycerol. The chain length of mycoloyl groups in this molecule ranged from 28 to 34 carbon atoms, being mono-, di- or triunsaturated. Detection of mycoloylglycerol by thin-layer chromatography may be thus useful for the rapid inclusion of a great variety of corynebacteria of clinical origin in the genus Corynebacterium in laboratories employing chromatographic techniques as an adjunct for the identification of these microorganisms.

Microbiological characterization and clinical significance of Corynebacterium amycolatum strains

The laboratory records of patients with bacillus isolates identified as Corynebacterium xerosis were reviewed in an attempt to establish the clinical significance of the isolates, and the isolated strains were reidentified. Of the 22 strains available for reidentification, four were identified as Corynebacterium striatum and 18 as Corynebacterium amycolatum. Forty-one patients were considered to have Corynebacterium amycolatum isolates, and in 13 (31.7%) of these patients a genuine clinical infection occurred, comprising catheter-related infection in seven cases, surgical wound infection in five cases, and pilonidal cyst infection in one case. Most patients were treated with antimicrobial agents (vancomycin in seven cases and amoxicillin/clavulanic acid in four cases). All patients were cured. Corynebacterium amycolatum can cause genuine infection, usually hospital-acquired, and the clinical significance of isolates must be determined to ensure proper management of patients.

Acyl phosphatidylglycerol: a major phospholipid of Corynebacterium amycolatum

The type strain and several clinical isolates of Corynebacterium amycolatum were examined for lipid composition as a chemotaxonomic character for routine identification. The phospholipid profile was composed of diphosphatidylglycerol, phosphatidylglycerol, phosphatidylinositol and phosphatidylinositol mannosides, together with various unidentified compounds. One of them, accounting for 20-29% of total phospholipids, was purified and characterized as acyl phosphatidylglycerol by chromatographic and spectrometric techniques. The acyl substituents on the phosphatidyl moiety were characterized as tetradecanoyl, pentadecanoyl, hexadecenoyl, hexadecanoyl, heptadecenoyl, heptadecanoyl, octadecenoyl (the major one), and octadecanoyl. The acyl group on the polar head (glycerol) was only octadecenoyl. Phospholipid analysis by thin-layer chromatography of a collection of Corynebacterium strains proved that this compound is widely distributed, although it only represents a minor (2-9%) component among mycolic acid-containing species. Acyl phosphatidylglycerol can be considered as a useful chemical marker for the identification of C. amycolatum in addition to the absence of mycolic acids.

[Evaluation of Mycobacterium fortuitum acyltrehaloses in the serologic diagnosis of pulmonary tuberculosis]

BACKGROUND

Several glycolipids of Mycobacterium tuberculosis are antigenic and their use in the serodiagnosis of pulmonary tuberculosis has been postulated. Acyltrehaloses (SL-IV) are among the strongest antigenic glycolipids of M. tuberculosis; similar compounds have been found in M. fortuitum. The aim of the present study was to evaluate the usefulness of the acyltrehaloses of M. fortuitum in the serodiagnosis of pulmonary tuberculosis.

METHODS

Two glycolipids, identified as triacyl- (TAT-MF) and diacyl- (DAT-MF) trehaloses, were studied by an ELISA method. Two independent analyses were carried out. In the first one, IgG and IgM were determined in sera from patients with pulmonary tuberculosis (84-24 bacteriologically not confirmed--), healthy individuals (46) and patients with respiratory pathologies other than pulmonary tuberculosis (38), using TAT-MF. In the second one, IgG was determined in sera from pulmonary tuberculosis patients (34) and from healthy individuals (20), using DAT-MF.

RESULTS

The sensitivity of the IgG ELISA using TAT-MF varied, according to the cut-off point, between 79.8 and 39.3%; the specificity values ranged between 83.3 and 98.8%. In sera from bacteriologically not confirmed pulmonary tuberculosis patients the sensitivity was 87.5-45.8%. The sensitivity for IgM was very low using TAM-MF (10.7-2.3%), with specificity values ranging from 77.4 to 100%. The sensitivity and specificity values of IgG using DAT-MF were, respectively, 34.3-9.3% and 90-100%.

CONCLUSIONS

The IgG ELISA using TAT-MF has similar values of sensitivity and specificity to those reported for the acyltrehaloses of M. tuberculosis, although this antigen, by itself, can not be used in the serodiagnosis of pulmonary tuberculosis. DAT-MF has no value in the serodiagnosis of pulmonary tuberculosis.

A family of diacyltrehaloses isolated from Mycobacterium fortuitum

A trehalose-containing glycolipid was detected in several strains of Mycobacterium fortuitum and characterized as 2,3-di-O-acyltrehalose (DAT) by combined NMR spectroscopy, IR spectroscopy, GLC and GLC-MS. Lipid constituents of the molecule were identified as a mixture of straight-chain (14-18 carbon atoms) and methyl-branched-chain (17-21 carbon atoms) fatty acyl groups. DAT was further fractionated by reverse phase TLC into four fractions that were designated DAT-I-DAT-IV. DAT-I contained 70-75% straight-chain acyl substituents (hexadecanoyl and octadecanoyl predominating) and 25-30% 2-methyl branched substituents (mainly 2-methyl octadecadienoyl). DAT-II was composed of a mixture in which the acyl groups were almost exclusively 2-methyl branched, with 2-methyl octadecadienoyl and 2-methyl octadecen-2-oyl predominating. DAT-III, which was the major isolated fraction, consisted of compounds in which the ratio linear to branched acyl groups varied between 0.8 to 0.9, 2-methyl octadecen-2-oyl, hexadecanoyl and octadecanoyl being the most abundant. Finally, DAT-IV comprised a mixture of DAT molecules containing mostly 2-methyl octadecadienoyl, 2-methyl octadecen-2-oyl, 2-methyl eicosadienoyl and 2-methyl eicosen-2-oyl groups.

Delineation of molecular species of a family of diacyltrehaloses from Mycobacterium fortuitum by mass spectrometry

A family of 2,3-di-O-acyl trehaloses (DAT), previously identified in Mycobacterium fortuitum, was studied by fast-atom bombardment mass spectrometry to establish the combinations of fatty acyl substituents and, hence, to delineate the molecular species there comprised. The mass spectra indicated the possible existence of 41 molecular species, with a total of 35-40 carbon atoms and 0-4 double bonds in the lipid moiety. The principal components were situated a m/z (M+ +23) 919 (formulated as 2-methyloctadec-2-enoyl,2-methyloctadecadienoyl trehalose and as 2-methylhexadec-2-enoyl,2-methyleicosadienoyl trehalose) and m/z (M+ +23) 921 (formulated as di-2-methyloctadec-2-enoyl trehalose and as 2-methylhexadec-2-enoyl,2-methyleicos-2-enoyl trehalose). The data obtained revealed that DAT was composed of three types of combinations of fatty acyl groups; (i) linear plus linear; (ii) linear plus 2-methyl branched; and (iii) 2-methyl branched plus 2-methyl branched.

Taxonomic implications of the chemical analysis of the D2 group of corynebacteria

Whole cell acid methanolysates from corynebacteria of the D2 group were found to contain meso-diaminopimelic acid, arabinose and galactose. Among lipids of taxonomic value, saturated and unsaturated straight chain fatty acids (14 to 18 carbon atoms), tuberculostearic acid (10-methyl octadecanoic acid) and mycolic acids were present. The last compounds ranged from 26 to 36 carbon atoms, the predominant types being 28.2, 28.1, 30.3, 30.2, 32.3 and 32.2. By reverse phase thin-layer chromatography the major menaquinone was identified as MK-9(H2)-containing nine isoprene units with two additional hydrogens. Moreover, diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol and phosphatidylinositol mannosides were detected among the phospholipids of these bacteria. Thus, on these bases, the D2 group appears to be closely related to the true corynebacteria.

Fatty acid composition and mycolic acid pattern of some chromogenic mycobacteria

Twenty-nine strains of chromogenic mycobacteria belonging to the species Mycobacterium aurum (5 strains), M. duvalii (2), M. flavescens (1), M. gordonae (6), M. kansasii (3), M. obuense (1), M. parafortuitum (3), M. phlei (2), M. rhodesiae (1), M. vaccae (2) and Mycobacterium spp. (3) were studied for fatty acid composition and mycolic acid patterns by gas-liquid chromatography and thin-layer chromatography respectively. Fatty acids found ranged from those with 12-24 carbon atoms and were saturated and monounsaturated straight chain fatty acids, along with 10-methyl branched of 16, 17 and 18 (tuberculostearic acid) carbon atoms. Moreover, 2-methyl tetradecanoic acid was found in M. gordonae, M. kansasii and Mycobacterium spp. (2 strains), and 2,4-dimethyl tetradecanoic acid in M. kansasii and Mycobacterium spp. (2 strains). Nonadecenoic acid was found only in M. flavescens and tuberculostearic acid was not detected in M. gordonae. Three patterns of mycolic acids were obtained: the first, found in M. aurum, M. flavescens, M. phlei, M. rhodesiae and Mycobacterium spp. (1 strain), was characterized by the presence of several spots assigned to alpha-mycolates, keto-mycolates and wax-ester mycolates (omega-carboxy-mycolates and 2-eicosanol and related alcohols); the second, found in M. duvalii, M. obuense, M. parafortuitum and M. vaccae was similar to the first, but it contained an additional spot of alpha'-mycolates; the third pattern, found in M. gordonae, M. kansasii and Mycobacterium spp. (2 strains) contained three spots considered to be alpha-mycolates, methoxy-mycolates and keto-mycolates. The results obtained confirm previously reported data on the fatty and mycolic acid composition of the species studied.

Nocardia in soils of southeastern Spain: abundance, distribution, and chemical characterisation

Actinomycetes belonging to the genus Nocardia were isolated from the surface horizon of 15 out of 46 soil samples examined. All the nocardiae strains isolated contained mycolic acids and saturated and unsaturated straight chain fatty acids (from 12 to 18 carbon atoms) and tuberculostearic acid and were biochemically identified as members of the Nocardia asteroides complex. Nocardiae were detected in alluvial, brown, and serosem great soil groups, but not in calcic brown, solontchack, and regosol great soil groups. Numbers of nocardiae isolated varied from 5.12 X 10(2) to 1.21 X 10(4) colony-forming units per gram of dry weight, and they were statistically correlated with the carbon content (percent C) of the soil. Soil samples were, in general, very dry.

A gas-liquid and thin-layer chromatographic study of Mycobacterium fortuitum

Forty-two strains of Mycobacterium fortuitum were examined for fatty acid composition by gas-liquid chromatography and for mycolic acid pattern by two dimensional thin-layer chromatography of whole cell acid methanolysates. The strains studied contained saturated and mono-unsaturated fatty acids from 12 to 24 carbon atoms and tuberculostearic acid, and they showed a thin-layer chromatographic pattern of mycolic acids similar to the pattern previously reported for this species and characterised by the presence of alpha and alpha'-mycolates and several more polar components. The heterogeneity within the species M. fortuitum, of its antigenic, biochemical and chemical properties, previously noted by several authors was slightly reflected (but not correlated) in the fatty acid composition found in the strains studied; the mycolic acid pattern of all of them was, however, very stable.