Fatty acid composition and mycolic acid pattern of some chromogenic mycobacteria

The HPLC-double-cluster pattern of some Mycobacterium gordonae strains is due to their dicarboxy-mycolate content

The mycolic acids of several strains of Mycobacterium gordonae were examined by chromatographic and spectroscopic techniques. Both HPLC and TLC revealed two patterns of mycolates among the M. gordonae strains studied. As determined by TLC, one pattern was composed of alpha-, methoxy- and keto-mycolates; the other was composed of these mycolates plus an additional component, which was identified as dicarboxy-mycolates. The dicarboxy-mycolates were only found in those M. gordonae strains that displayed a so-called HPLC-double-cluster pattern. Detailed structural analyses of the dicarboxy-mycolates indicated that these compounds contained predominantly 61-65 carbon atoms (C(63) was the major component) and a trans-1,2-disubstituted cyclopropane ring. Thus, the dicarboxy-mycolate content of strains of M. gordonae determines their HPLC pattern. In spite of the differences in their HPLC patterns, and although they belonged to different PCR-restriction length polymorphism clusters, all of the M. gordonae strains examined in this study were closely related on the basis of the structural features of their alpha-, keto- and methoxy-mycolates; the predominant alpha-mycolates contained two cis-1,2-disubstituted cyclopropane rings, the major keto-mycolates contained a trans-1,2-disubstituted cyclopropane ring and the methoxy-mycolates contained one cis- or one trans-1,2-disubstituted cyclopropane ring. It is noteworthy that the strains containing dicarboxy-mycolates also displayed significant amounts of alpha-mycolates that contained one cis-1,2-disubstituted cyclopropane ring and one cis double bond. The results obtained in this study demonstrate heterogeneity among M. gordonae strains.

Analysis of the structural diversity of mycolic acids of Rhodococcus and Gordonia [correction of Gordonla] isolates from activated sludge foams by selective ion monitoring gas chromatography-mass spectrometry (SIM GC-MS)

A method using Selective Ion Monitoring (SIM) gas chromatography-mass spectrometry is described for analysis of mycolic acids which reveals a hitherto unrecognised chemical structural diversity among these in some members of the Mycolata. The structural interpretation of mass spectral data of mycolic acids from Rhodococcus spp and Gordonia [corrected] spp using SIM is discussed.

Current techniques in mycobacterial detection and speciation

Tuberculosis, a health concern so well controlled in recent decades that eradication seemed imminent, is once again reaching epidemic proportions following the increasing prevalence of AIDS. One important means of curbing this resurgence is a robust method that has the capability of identifying and speciating mycobacterial infections in a matter of days. Classic biochemical techniques, which require 4 to 8 weeks to identify and speciate tuberculosis infections, are in the process of being replaced by newer methods, including BACTEC, gene probes, nucleic acid amplification, amplification of ribosomal RNA, high-performance liquid chromatography, and gas chromatography-mass spectrometry. This review is intended to give the reader a synopsis of the current literature and research on these methods, including reliability, approximate time required for detection and speciation, and clinical utility.

Gas chromatography/tandem mass spectrometry as an analytical tool for the identification of fatty acids

Structures of fatty acids present at very low quantities in mycobacteria are difficult to determine. A commonly used strategy is to introduce heteroatoms into functional groups by chemical means before subjecting them to gas chromatography/tandem mass spectrometry (GC/MS/MS) analysis. Routinely used methods give very low abundance diagnostic ions leading to ambiguities in structural conclusions. GC/MS/MS associated with electron capture ionization of pentafluorobenzyl esters was used to study very complex mixtures of fatty acids from Mycobacterium fallax and M. aurum. The charge-remote fragmentation of fatty acid carboxylate anions was used for structure determination at the nanogram level of a large number of unsaturated, branched, and cyclopropane-containing fatty acids. Some of them have not been observed previously in these Mycobacteria. On the basis of these studies, biosynthetic pathways of unsaturated, branched, and cyclopropane-containing fatty acid are proposed.

Mycobacterial identification by computer-aided gas-liquid chromatography

The suitability of the Microbial Identification System (MIS) marketed by Microbial ID (Newark, DE, USA) for routine diagnosis of clinically important mycobacteria was investigated and assessed. Cellular fatty acids were extracted from 1077 stock and recent clinical isolates. They were analyzed using a gas-liquid chromatograph combined with MIS software. The MIS system finally identifies the isolates by comparing their fatty-acid compositions with a standard library for mycobacteria. As the library search usually results in more than one possible match, suitable identification criteria were determined. The stricter these criteria are, the more the percentage of false-positive identifications can be reduced, but at the cost of more cases that remain undecided and require additional analysis. Under conditions similarity index (SI) SI1 > or = 0.4 and SI1-SI2 > or = 0.1, 63% of all isolates were correctly and 6% incorrectly identified.

Gas chromatographic whole-cell fatty acid analysis as an aid for the identification of mixed mycobacterial cultures

Gas chromatographic analysis of whole-cell fatty acids, secondary alcohols and mycolic acid cleavage products could be a useful technique in checking mixed mycobacterial cultures. The mixed cultures were confirmed when species-specific compounds of different mycobacterial species were detected in the same chromatogram.

Identification of mycobacterial isolates by thin-layer and capillary gas-liquid chromatography under diagnostic routine conditions

The mycolic acid patterns of 75 strains of mycobacteria belonging to 46 different species were studied by thin-layer chromatography (TLC). Additionally, the mycolic acid pyrolytic cleavage products were determined by capillary gas-liquid chromatography (C-GLC). Eleven different patterns based on number, type and Rf values of the detected lipid spots were identified. The mycolic acid methyl ester profiles of clinical isolates were compared with those of reference strains. In this way, it was possible to relate these clinical isolates to mycobacterial groups defined by their mycolic acid profiles. The 11 patterns and the methods used are described in detail.

Evaluation of practical chromatographic procedures for identification of clinical isolates of mycobacteria

After experimental conditions were established, 366 strains of mycobacteria belonging to 23 different species were studied for fatty acids, secondary alcohols, and mycolic acid cleavage products by capillary gas-liquid chromatography. Additionally, the mycolic acid pattern was studied by thin-layer chromatography. Capillary gas-liquid chromatography allowed direct identification of the following Mycobacterium spp.: M. kansasii, M. marinum, M. szulgai, M. xenopi, M. malmoense, and M. gordonae. The patterns of mycolic acid methyl esters recorded for the test strains of M. chelonae and M. agri may be of value in the identification of these species. Moreover, the combined use of the two chromatographic techniques provided precise identification of the M. tuberculosis complex, M. simiae, M. fallax, M. triviale, and M. chelonae-like organisms. A minimal set of biochemical tests is usually required to obtain identification to the species level when chromatographic procedures alone are not sufficient. Under the reported experimental conditions, thin-layer chromatography and capillary gas-liquid chromatography are rapid and very useful techniques for the identification of mycobacteria.

Gas chromatography of mycobacterial fatty acids and alcohols: diagnostic applications

Capillary gas chromatography of cellular fatty acids and alcohols has been used as a routine method for a period of two years in the mycobacterial diagnostic laboratory of Statens institutt for folkehelse, Oslo, Norway. All mycobacteria (165 isolates) other than Mycobacterium tuberculosis (MOTT) and 24 randomly selected M. tuberculosis isolates were studied. Twelve characteristic lipid constituents allowed the construction of a diagnostic scheme. Without exceptions, all 36 examined isolates belonging to the M. tuberculosis-complex were characterized by a relatively high concentration level of hexacosanoic acid (mean: 4%, range: 1-13%), low level of tetracosanoic acid (mean: 1%, range: 0.1-3%), lack of methylbranched acids other than tuberculostearic acid, and lack of fatty alcohols. Members of the MAIS-complex (73 isolates) were all characterized by the general presence of the fatty alcohols 2-octadecanol (mean: 2%, range: 0.1-5%) and 2-eicosanol (mean: 7%, range: 2-21%), relatively high levels of tetracosanoic acid (mean: 5%, range: 1-15%) and lack (or trace) of hexacosanoic acid and methylbranched acids other than tuberculostearic acid. All 16 isolates of M. gordonae were easily recognized by their unique lack of tuberculostearic acid and their content of 2-methyl-tetradecanoic acid (mean: 5%, range: 2-12%), and the M. xenopi isolates were the only examined strains containing the fatty alcohol 2-docosanol (mean: 9%, range: 2-13%). The six M. malmoense strains contained the two unique constituents 2-methyl eicosanoic acid (mean: 3%, range: 1-4%) and 2,4,6-trimethyl tetracosanoic acid (mean: 3%, range: 2-4%). The ten strains of M. kansasii were characterized by 2,4-dimethyl tetradecanoic acid (mean: 5%, range: 1-11%), whereas the seven strains of M. marinum shared 2,4-dimethyl hexadecanoic acid (mean: 4%, range 0.2-12%) as a specific marker.

Storage of sialic acid-containing carbohydrates in the placenta of a human galactosialidosis fetus. Isolation and structural characterization of 16 sialyloligosaccharides

From the placenta of a human fetus with galactosialidosis, detected by prenatal diagnosis, sialyloligosaccharides were isolated by successively gel-permeation chromatography on Bio-Gel P-6, anion-exchange chromatography on Mono Q and high-performance liquid chromatography on Lichrosorb-NH2. 16 sialic acid-containing N-glycosidic N-acetyllactosamine type of structures were identified by sugar analysis and 500-MHz 1H-NMR spectroscopy. The fully sialylated oligosaccharides differ from each other in the type of branching (mono-, di-, tri-, tri'- and tetra-antennary) or sialic acid linkage types (alpha 2-3/alpha 2-6). The isolated carbohydrates, including six novel structures, can be presented as follows (the numerals in a column represents one compound). (formula; see text).

A thin-layer chromatographic method for separating methyl esters of mycobacterial mycolic acids

A two-dimensional thin-layer chromatographic method was developed which allowed separation of the different mycobacterial mycolic acids as methyl esters. Dichloromethane (once) and petroleum ether:acetone (95:5, v/v twice or three times) were used as solvents. Alkaline saponification of freeze-dried cells followed by methylation of the mycolic acids using iodomethane gave satisfactory results, whereas methylation using boron trichloride-methanol complex or trans-esterification through direct acid methanolysis was found to degrade epoxy-mycolates. The chromatographic method developed here is rapid and informative, and should prove valuable in routine mycobacterial differentiation.

Differentiation of Mycobacterium thermoresistibile from Mycobacterium phlei and other rapidly growing mycobacteria

Mycobacterium thermoresistibile is the only chromogenic rapidly growing mycobacterial species reported to cause infections in humans and animals. DNA-DNA hybridization (S1 nuclease method) showed that M. thermoresistibile formed a DNA relatedness group which was only 24 to 30% related to M. phlei. Alkaline phosphatase and beta-galactosidase differentiated M. thermoresistibile from M. phlei. Among the rapidly growing mycobacteria, the mycolic acid pattern of M. thermoresistibile was unique (alpha-, alpha'-, methoxy-and keto-mycolates). Fourteen other species of chromogenic rapidly growing mycobacteria, including M. phlei, produced different mycolic acid patterns which always included dicarboxylic mycolate. Nine species of non-chromogenic rapidly growing mycobacteria produced mycolic acid patterns devoid of ketomycolate.