Gas-chromatographic analysis of mycolic acid cleavage products in mycobacteria

Description of Corynebacterium poyangense sp. nov., isolated from the feces of the greater white-fronted geese (Anser albifrons)

Two novel Gram-positive, non-spore-forming, facultatively anaerobic, non-motile, and short rods to coccoid strains were isolated from the feces of the greater white-fronted geese (Anser albifrons) at Poyang Lake. The 16S rRNA gene sequences of strains 4H37-19^T and 3HC-13 shared highest identity to that of Corynebacterium uropygiale Iso10^T (97.8%). Phylogenetic and phylogenomic analyses indicated that strains 4H37-19^T and 3HC-13 formed an independent clade within genus Corynebacterium and clustered with Corynebacterium uropygiale Iso10^T. The average nucleotide identity and digital DNA-DNA hybridization value between strains 4H37-19^T and 3HC-13 and members within genus Corynebacterium were all below 95% and 70%, respectively. The genomic G + C content of strains 4H37-19^T and 3HC-13 was 52.5%. Diphosphatidylglycerol (DPG), phosphatidylglycerol (PG), phosphatidylinositol (PI), phosphatidylcholine, and phosphatidyl inositol mannosides (PIM) were the major polar lipids, with C_18:1ω9c, C_16:0, and C_18:0 as the major fatty acids, and MK-8 (H4), MK-8(H₂), and MK-9(H₂) as the predominant respiratory quinones. The major whole cell sugar was arabinose, and the cell wall included mycolic acids. The cell wall peptidoglycan contained meso-diaminopimelic acid (meso-DAP). The polyphasic taxonomic data shows that these two strains represent a novel species of the genus Corynebacterium, for which the name Corynebacterium poyangense sp. nov. is proposed. The type strain of Corynebacterium poyangense is 4H37-19^T (=GDMCC 1.1738^T = KACC 21671^T).

Characterization of Mycobacterium tuberculosis Mycolic Acids by Multiple-Stage Linear Ion-Trap Mass Spectrometry

Mycobacterium tuberculosis (Mtb) cells are known to synthesize very long chain (C60-90) structurally complex mycolic acids with various functional groups. In this study, we applied linear ion-trap (LIT) multiple-stage mass spectrometry (MSn), combined with high-resolution mass spectrometry to study the mechanisms underlying the fragmentation processes of mycolic acid standards desorbed as lithiated adduct ions by ESI. This is followed by structural characterization of a Mtb mycolic acid family (Bovine strain). Using the insight fragmentation processes gained from the study, we are able to achieve a near complete characterization of the whole mycolic acid family, revealing the identity of the α-alkyl chain, the location of the functional groups including methyl, methoxy, and keto groups along the meroaldehyde chain in each lipid species. This study showcased the power of LIT MSn toward structural determination of complex lipids in a mixture, which would be otherwise very difficult to define using other analytical techniques.

Application of Thin-Layer Chromatography-Flame Ionization Detection (TLC-FID) to Total Lipid Quantitation in Mycolic-Acid Synthesizing Rhodococcus and Williamsia Species

In addition to cell membrane phospholipids, Actinobacteria in the order Corynebacteriales possess a waxy cell envelope containing mycolic acids (MA). In optimized culture condition, some species can also accumulate high concentrations of intracellular triacylglycerols (TAG), which are a potential source of biodiesel. Bacterial lipid classes and composition alter in response to environmental stresses, including nutrient availability, thus understanding carbon flow into different lipid classes is important when optimizing TAG synthesis. Quantitative and qualitative analysis of lipid classes normally requires combinations of different extraction, derivatization, chromatographic and detection methods. In this study, a single-step thin-layer chromatography-flame ionization detection (TLC-FID) technique was applied to quantify lipid classes in six sub-Antarctic Corynebacteriales strains identified as Rhodococcus and Williamsia species. A hexane:diethyl-ether:acetic acid solvent system separated the total cellular lipids extracted from cells lysed by bead beating, which released more bound and unbound MA than sonication. Typical profiles included a major broad non-polar lipid peak, TAG and phospholipids, although trehalose dimycolates, when present, co-eluted with phospholipids. Ultra-performance liquid chromatography-tandem mass-spectrometry and nuclear magnetic resonance spectroscopy detected MA signatures in the non-polar lipid peak and indicated that these lipids were likely bound, at least in part, to sugars from cell wall arabinogalactan. Waxy esters were not detected. The single-solvent TLC-FID procedure provides a useful platform for the quantitation and preliminary screening of cellular lipid classes when testing the impacts of growth conditions on TAG synthesis.

Advances in the molecular diagnosis of tuberculosis: From probes to genomes

Tuberculosis, disease caused by Mycobacterium tuberculosis, is currently the leading cause of death by a single infectious agent worldwide. Early, rapid and accurate identification of M. tuberculosis and the determination of drug susceptibility is essential for the treatment and management of this disease. Tuberculosis diagnosis is mainly based on chest radiography, smear microscopy and bacteriological culture. Smear microscopy has variable sensitivity, mainly in patients co-infected with the human immunodeficiency virus (HIV). Conventional culture for M. tuberculosis isolation, identification and drug susceptibility testing requires several weeks owning to the slow growth of M. tuberculosis. The delay in the time to results drives the prolongation of potentially inappropriate antituberculosis therapy contributing to the emergence of drug resistance, reducing treatment options and increasing treatment duration and associated costs, resulting in increased mortality and morbidity. For these reasons, novel diagnostic methods are need for timely identification of M. tuberculosis and determination of the antibiotic susceptibility profile of the infecting strain. Molecular methods offer enhanced sensitivity and specificity, early detection and the capacity to detect mixed infections. These technologies have improved turnaround time, cost effectiveness and are amenable for point-of-care testing. However, although these methods produce results within hours from sample collection, the phenotypic susceptibility testing is still needed for the determination of drug susceptibility and quantify the susceptibility levels of a given strain towards individual antibiotics. This review presents the history, advances and forthcoming promises in the molecular diagnosis of tuberculosis. An overview on the general principles, diagnostic value and the main advantages and disadvantages of the molecular methods used for the detection and identification of M. tuberculosis and its associated disease, is provided. It will be also discussed how the current phenotypic methods should be used in combination with the genotypic methods for rapid antituberculosis susceptibility testing.

Mycobacteriophage putative GTPase-activating protein can potentiate antibiotics

The soaring incidences of infection by antimicrobial resistant (AR) pathogens and shortage of effective antibiotics with new mechanisms of action have renewed interest in phage therapy. This scenario is exemplified by resistant tuberculosis (TB), caused by resistant Mycobacterium tuberculosis. Mycobacteriophage SWU1 A321_gp67 encodes a putative GTPase-activating protein. Mycobacterium smegmatis with gp67 overexpression showed changed colony formation and biofilm morphology and supports the efficacy of streptomycin and capreomycin against Mycobacterium. gp67 down-regulated the transcription of genes involved in cell wall and biofilm development. To our knowledge, this is the first report to show that phage protein in addition to lysin or recombination components can synergize with existing antibiotics. Phage components might represent a promising new clue for better antibiotic potentiators.

Direct detection of Mycobacterium tuberculosis in sputum: A validation study using solid phase extraction-gas chromatography-mass spectrometry

Tuberculosis (TB) remains a worldwide health problem, especially in developing countries. Correct identification of Mycobacterium tuberculosis (MTB) infection is extremely important for providing appropriate treatment and care to patients. Here we describe a solid phase extraction-gas chromatography-mass spectrometry method (SPE-THM-GC-MS) for the detection of five biomarkers for M. tuberculosis. The method for classification is developed and validated through the analysis of 112 sputum samples from patients suspected of having TB. Twenty of twenty-five MTB culture-positive sputum samples were correctly classified as positive by our improved SPE-THM-GC-MS method. Eighty-five of eighty-seven MTB culture-negative samples were also negative by SPE-THM-GC-MS. The overall sensitivity of the new SPE-THM-GC-MS method is 80% (20/25) and the specificity is 98% (85/87) compared with culture. The method proved to be reliable and, although complex in principle, easy to operate due to the high degree of automation.

Characterization of Mycolic Acids in Total Fatty Acid Methyl Ester Fractions from Mycobacterium Species by High Resolution MALDI-TOFMS

Mycolic acids (MAs) are characteristic components of bacteria in the suborder Corynebacterineae, such as Mycobacterium. MAs are categorized into subclasses based on their functional bases (cyclopropane ring, methoxy, keto, and epoxy group). Since MAs have heterogeneity among bacterial species, analyzing of MAs are required in the chemotaxonomic field. However, their structural analysis is not easy because of their long carbon-chain lengths and several functional groups. In this study, total fatty acid (FA) methyl ester (ME) fraction of M. tuberculosis H37Rv was analyzed by matrix-assisted laser desorption/ionization (MALDI) time-of-flight mass spectrometry (TOFMS) with a spiral ion trajectory (MALDI spiral-TOFMS). The distributions of carbon-chain length and their relative peak intensities were confirmed with those obtained by analysis of each subclass fraction which was separated from total FA ME fraction using thin-layer chromatography (TLC). The observed major peaks were reliably assigned as MAs owing to the high mass accuracy (error<3 ppm). The types of MA subclasses, their distributions of carbon-chain lengths, their relative peak intensities, and the ratio of even- and odd-numbered carbon-chain MAs for the total FA ME fraction were consistent with those of MA subclass fractions. To visualize whole MAs, contour maps of relative peak intensities for whole MAs were created. The contour maps indicated the MA subclasses and their distributions of carbon-chains with relative peak intensities at a glance. Our proposed method allows simple characterization in a short time and thus enables the analysis of large numbers of samples, and it would contribute to the chemotaxonomy.

A comparison of four sputum pre-extraction preparation methods for identifying and characterising Mycobacterium tuberculosis using GCxGC-TOFMS metabolomics

In many pulmonary diseases, sputum is a valuable sample material for use in disease characterisation and diagnostics. However, due to its high viscosity and uneven consistency (lumpiness), it is difficult to obtain reproducible/repeatable results during compound extraction and analysis. We subsequently investigated and compared four sputum pre-extraction preparation methods using: 1) Sputolysin; 2) a combination of N-acetyl-l-cysteine and sodium hydroxide (NALC-NaOH); 3) NaOH alone, and 4) a simple ethanol homogenisation method, prior to sputum extraction and metabolomics analyses. The simple ethanol homogenisation approach proved to be the comparatively superior sputum pre-extraction preparation method, considering its repeatability, the number of characteristic compounds extracted, its ability to extract those compounds best differentiating the sample groups (Mycobacterium tuberculosis-spiked and clinically confirmed TB-positive patient samples from each of the controls respectively), and its detection limit. This developed methodology subsequently allows for accurate GC based analyses of sputum, and hence, could contribute significantly to the better characterisation or diagnostics of not only tuberculosis, but also potentially other pulmonary diseases, including, interstitial lung disease, cystic fibrosis, lung cancer, pneumonia and any other bacterial induced pulmonary diseases producing sputum.

A metabolomics approach to characterise and identify various Mycobacterium species

We investigated the potential use of gas chromatography mass spectrometry (GC-MS), in combination with multivariate statistical data processing, to build a model for the classification of various tuberculosis (TB) causing, and non-TB Mycobacterium species, on the basis of their characteristic metabolite profiles. A modified Bligh-Dyer extraction procedure was used to extract lipid components from Mycobacterium tuberculosis, Mycobacterium avium, Mycobacterium bovis, and Mycobacterium kansasii cultures. Principle component analyses (PCA) of the GC-MS generated data showed a clear differentiation between all the Mycobacterium species tested. Subsequently, the 12 compounds best describing the variation between the sample groups were identified as potential metabolite markers, using PCA and partial least-squares discriminant analysis (PLS-DA). These metabolite markers were then used to build a discriminant classification model based on Bayes' theorem, in conjunction with multivariate kernel density estimation. This model subsequently correctly classified 2 "unknown" samples for each of the Mycobacterium species analysed, with probabilities ranging from 72 to 100%. Furthermore, Mycobacterium species classification could be achieved in less than 16 h, and the detection limit for this approach was 1×10(3)bacteriamL(-1). This study proves the capacity of a GC-MS, metabolomics pattern recognition approach for its possible use in TB diagnostics and disease characterisation.

Electrospray ionization-tandem mass spectrometry analysis of the mycolic acid profiles for the identification of common clinical isolates of mycobacterial species

Mycolic acids are unique and complex molecular structures found in mycobacterial species. In the present study, we investigated whether electrospray ionization-tandem mass spectrometry (ESI-MS/MS) can be used to identify mycobacterial species based on their mycolic acid profiles. Clinical isolates of Mycobacterium tuberculosis complex and 18 nontuberculosis mycobacterial (NTM) species identified by PCR-restriction fragment length polymorphism (RFLP) or real-time PCR were used for this analysis. Crude lipid extracts were prepared by saponifying 1-2 colonies of individual isolates of mycobacterial species and by chloroform and methanol (2:1, v/v) extraction. ESI-MS/MS in negative ion mode with high cone voltage and collision energy was used for mycolic acid profiling analysis. Combinatorial precursor ion scans of m/z 395, 367, and 339 in the range of m/z 1000-1400 resulted in spectra specific to individual mycobacteria. M. tuberculosis complex and M. pulveris showed major ions by performing precursor ion scans on m/z 395 and 367, while other NTM species showed major ions by performing scans on m/z 367 and 339. The different NTM species examined showed different species dependent mycolic acid profiles. In conclusion, we describe a rapid, reliable, and informative ESI-MS/MS protocol for mycolic acid profiling in mycobacterial species, which allows mycobacterial species to be easily identified in clinical laboratories.

Identification of mycobacteria of the MAIS Complex and M. tuberculosis by restriction fragment length polymorphism analysis of hsp65 gene

Restriction fragment length polymorphism analysis of hsp65 gene was performed on museum strains of mycobacteria using Hin6I restrictase. Study of restriction profiles allowed us to distinguish mycobacterial species of the MAIS complex and several strains of nontuberculous mycobacteria.

Deletion of kasB in Mycobacterium tuberculosis causes loss of acid-fastness and subclinical latent tuberculosis in immunocompetent mice

Mycobacterium tuberculosis, the causative agent of tuberculosis, has two distinguishing characteristics: its ability to stain acid-fast and its ability to cause long-term latent infections in humans. Although this distinctive staining characteristic has often been attributed to its lipid-rich cell wall, the specific dye-retaining components were not known. Here we report that targeted deletion of kasB, one of two M. tuberculosis genes encoding distinct beta-ketoacyl- acyl carrier protein synthases involved in mycolic acid synthesis, results in loss of acid-fast staining. Biochemical and structural analyses revealed that the DeltakasB mutant strain synthesized mycolates with shorter chain lengths. An additional and unexpected outcome of kasB deletion was the loss of ketomycolic acid trans-cyclopropanation and a drastic reduction in methoxymycolic acid trans-cyclopropanation, activities usually associated with the trans-cyclopropane synthase CmaA2. Although deletion of kasB also markedly altered the colony morphology and abolished classic serpentine growth (cording), the most profound effect of kasB deletion was the ability of the mutant strain to persist in infected immunocompetent mice for up to 600 days without causing disease or mortality. This long-term persistence of DeltakasB represents a model for studying latent M. tuberculosis infections and suggests that this attenuated strain may represent a valuable vaccine candidate against tuberculosis.

Requirement of the mymA operon for appropriate cell wall ultrastructure and persistence of Mycobacterium tuberculosis in the spleens of guinea pigs

We had recently reported that the mymA operon (Rv3083 to Rv3089) of Mycobacterium tuberculosis is regulated by AraC/XylS transcriptional regulator VirS (Rv3082c) and is important for the cell envelope of M. tuberculosis. In this study, we further show that a virS mutant (MtbdeltavirS) and a mymA mutant (Mtbmym::hyg) of M. tuberculosis exhibit reduced contents and altered composition of mycolic acids along with the accumulation of saturated C24 and C26 fatty acids compared to the parental strain. These mutants were markedly more susceptible to major antitubercular drugs at acidic pH and also showed increased sensitivity to detergent (sodium dodecyl sulfate) and to acidic stress than the parental strain. We show that disruption of virS and mymA genes impairs the ability of M. tuberculosis to survive in activated macrophages, but not in resting macrophages, suggesting the importance of the mymA operon in protecting the bacterium against harsher conditions. Infection of guinea pigs with MtbdeltavirS, Mtbmym::hyg, and the parental strain resulted in an approximately 800-fold-reduced bacillary load of the mutant strains compared with the parental strain in spleens, but not in the lungs, of animals at 20 weeks postinfection. Phenotypic traits were fully complemented upon reintroduction of the virS gene into MtbdeltavirS. These observations show the important role of the mymA operon in the pathogenesis of M. tuberculosis at later stages of the disease.

Characterization of a novel group of mycobacteria and proposal of Mycobacterium sherrisii sp. nov

We describe here the characterization of five isolates of Mycobacterium simiae-like organisms representing a novel group based on whole-cell fatty acid analysis and genotypic evaluation. Two of the five isolates in this study, W55 and W58, were previously considered to belong to M. simiae serotype 2. Analysis of cellular fatty acids by gas-liquid chromatography indicated a close clustering of this group, which was well differentiated from the other M. simiae-like species. Molecular characterization was performed by nucleic acid sequencing of the small subunit rRNA gene and the gene encoding the 65-kDa heat shock protein and genomic DNA hybridization. Sequence analysis of the entire 16S rRNA gene showed a unique sequence most closely related to those of M. triplex and M. simiae. The hsp65 partial gene sequence was identical for the five isolates, with 97% identity to the M. simiae type strain. However, qualitative whole genomic DNA hybridization analysis confirmed that this group is genetically distinct from M. simiae and M. triplex. Antimicrobial susceptibilities for this group resemble those of M. simiae and M. lentiflavum. We conclude that this group represents a unique Mycobacterium species for which we propose the name Mycobacterium sherrisii sp. nov.

Impact of genotypic studies on mycobacterial taxonomy: the new mycobacteria of the 1990s

The advancement of genetic techniques has greatly boosted taxonomic studies in recent years. Within the genus Mycobacterium, 42 new species have been detected since 1990, most of which were grown from clinical samples. Along with species for which relatively large numbers of strains have been reported, some of the new species of mycobacteria have been detected rarely or even only once. From the phenotypic point of view, among the new taxa, chromogens exceed nonchromogens while the numbers of slowly and rapidly growing species are equivalent. Whereas conventional identification tests were usually inconclusive, an important role was played by lipid analyses and in particular by high-performance liquid chromatography. Genotypic investigations based on sequencing of 16S rRNA gene have certainly made the most important contribution. The investigation of genetic relatedness led to the redistribution of the species previously included in the classically known categories of slow and rapid growers into new groupings. Within slow growers, the intermediate branch related to Mycobacterium simiae and the cluster of organisms related to Mycobacterium terrae have been differentiated; among rapid growers, the group of thermotolerant mycobacteria has emerged. The majority of species are resistant to isoniazid and, to a lesser extent, to rifampin. Many of the new species of mycobacteria are potentially pathogenic, and there are numerous reports of their involvement in diseases. Apart from disseminated and localized diseases in immunocompromised patients, the most frequent infections in immunocompetent people involve the lungs, skin, and, in children, cervical lymph nodes. The awareness of such new mycobacteria, far from being a merely speculative exercise, is therefore important for clinicians and microbiologists.

Burden of unidentifiable mycobacteria in a reference laboratory

Modern identification techniques at the genomic level have greatly improved the taxonomic knowledge of mycobacteria. In adjunct to nucleic acid sequences, mycobacterial identification has been endorsed by investigation of the lipidic patterns of unique mycolic acids in such organisms. In the present investigation, the routine use of high-performance liquid chromatography (HPLC) of mycolic acids, followed by the sequencing of the 16S rRNA, allowed us to select 72 mycobacterial strains, out of 1,035 screened, that do not belong to any of the officially recognized mycobacterial species. Most strains (i.e., 47) were isolated from humans, 13 were from the environment, 3 were from animals, and 9 were from unknown sources. The majority of human isolates were grown from the respiratory tract and were therefore most likely not clinically significant. Some, however, were isolated from sterile sites (blood, pleural biopsy, central venous catheter, or pus). Many isolates, including several clusters of two or more strains, mostly slow growers and scotochromogenic, presented unique genetic and lipidic features. We hope the data reported here, including the results of major conventional identification tests, the HPLC profiles of strains isolated several times, and the whole sequences of the 16S rRNA hypervariable regions of all 72 mycobacteria, may encourage reporting of new cases. The taxonomy of the genus Mycobacterium is, in our opinion, still far from being fully elucidated, and the reporting of unusual strains provides the best background for the recognition of new species. Our report also shows the usefulness of the integration of novel technology to routine diagnosis, especially in cases involving slow-growing microorganisms such as mycobacteria.

Direct identification of Mycobacterium species in Bactec 7H12B medium by gas-liquid chromatography

Twenty-nine Mycobacterium reference strains representing 10 species and 60 mycobacterial cultures isolated from sputum specimens were studied. These cultures were grown in Bactec 7H12B medium (Becton Dickinson and Co., Paramus, N.J.) supplemented with oleic acid-albumin-dextrose-catalase enrichment broth (Becton Dickinson and Co., Cockeysville, Md.). The cultures were analyzed by gas-liquid chromatography for their fatty acids, secondary alcohols, and mycolic acid cleavage products. All of the clinical isolates could be identified by comparing their gas-liquid chromatography profiles with those of the reference strains. The data indicate that this method significantly shortens the turnaround time and could be used for the early detection and identification of mycobacterial species.

Distribution of C22-, C24- and C26-alpha-unit-containing mycolic acid homologues in mycobacteria

There are three mycolic acid homologues with C22-, C24- and C26-alpha-units in Mycobacterium. In order to reveal the composition and distribution of these homologues in each subclass and molecular species of mycolic acids and to compare them with the composition of constitutive non-polar fatty acids (free and bound forms), we have separated non-polar fatty acids and each subclass of mycolic acids from 21 mycobacterial species by thin-layer chromatography, and analyzed non-polar fatty acid methyl esters by gas chromatography (GC) and the cleavage products of methyl mycolate by pyrolysis GC. We further performed mass chromatographic analysis of trimethylsilyl (TMS) ether derivatives of mycolic acid methyl esters by monitoring [B-29]+ ions (loss of CHO from the alpha-branched-chain structure of mycolic acids) of m/z 426, 454 and 482 which are attributed to C22-, C24- and C26-alpha-units of TMS ether derivatives of methyl mycolates, respectively, (Kaneda, K. et al, J. Clin. Microbiol. 24: 1060-1070, 1986). By pyrolysis GC, C22:0, C24:0 and C26:0 fatty acid methyl esters generated by the C2-C3 cleavage of C22-, C24- and C26-alpha-unit-containing mycolic acid methyl esters, respectively, were detected. Their proportion was almost the same among subclasses of mycolic acids in every Mycobacterium and also similar to the proportion of constitutive non-polar C22:0, C24:0 and C26:0 fatty acids. By mass chromatography, the composition and distribution of C22- and C24-alpha-unit-containing homologues were revealed to be similar between alpha- and alpha'-mycolic acids in every Mycobacterium.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Clinical significance, biochemical features, and susceptibility patterns of sporadic isolates of the Mycobacterium chelonae-like organism

Mycobacterium chelonae-like organisms are nonpigmented rapidly growing mycobacteria whose clinical significance is unknown. We evaluated 87 sporadic isolates encountered in a clinical laboratory. Most isolates (62%) were respiratory; only 2 of 54 (4%) (both from patients with AIDS) were clinically significant. Among 33 nonrespiratory isolates, 20 of 33 (or 61%) were clinically significant. Clinical diseases included posttraumatic wound infections and catheter-related sepsis. Routine biochemical features included growth inhibition by 5% NaCl (100%), a smooth colony morphology (94%), positive 3-day arylsulfatase reaction (84%), no color or a light tan color on iron uptake (100%), and variable nitrate reduction (45%). Additional characteristics that helped to separate this group from M. chelonae and Mycobacterium abscessus were susceptibility to cephalothin (90%) and ciprofloxacin (100%), utilization of mannitol (94%) and citrate (83%) as carbon sources, and unique patterns of mycolic acid esters by high-performance liquid chromatography. This group was quite drug susceptible, with 100% of isolates inhibited by amikacin, imipenem, cefoxitin, cefmetazole, and the newer quinolones ciprofloxacin and ofloxacin. Three examples of this group, including a proposed type strain, have been deposited in the American Type Culture Collection.

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.

Applications of cellular fatty acid analysis

More than ever, new technology is having an impact on the tools of clinical microbiologists. The analysis of cellular fatty acids by gas-liquid chromatography (GLC) has become markedly more practical with the advent of the fused-silica capillary column, computer-controlled chromatography and data analysis, simplified sample preparation, and a commercially available GLC system dedicated to microbiological applications. Experience with applications in diagnostic microbiology ranges from substantial success in work with mycobacteria, legionellae, and nonfermentative gram-negative bacilli to minimal involvement with fungi and other nonbacterial agents. GLC is a good alternative to other means for the identification of mycobacteria or legionellae because it is rapid, specific, and independent of other specialized testing, e.g., DNA hybridization. Nonfermenters show features in their cellular fatty acid content that are useful in identifying species and, in some cases, subspecies. Less frequently encountered nonfermenters, including those belonging to unclassified groups, can ideally be characterized by GLC. Information is just beginning to materialize on the usefulness of cellular fatty acids for the identification of gram-positive bacteria and anaerobes, despite the traditional role of GLC in detecting metabolic products as an aid to identification of anaerobes. When species identification of coagulase-negative staphylococci is called for, GLC may offer an alternative to biochemical testing. Methods for direct analysis of clinical material have been developed, but in practical and economic terms they are not yet ready for use in the clinical laboratory. Direct analysis holds promise for detecting markers of infection due to an uncultivable agent or in clinical specimens that presently require cultures and prolonged incubation to yield an etiologic agent.

Chemotypes of Mycobacterium malmoense based on glycolipid profiles

Thin-layer chromatographic analysis of 72 Finnish clinical mycobacterial isolates presumptively identified as Mycobacterium malmoense revealed four major glycolipid profiles with two minor variations. An additional glycolipid profile was found in three British M. malmoense-like strains. No clear distinction between the strains could be made by means of gas chromatography of cellular fatty acids. The two M. malmoense-specific constituents, 2-methyleicosanoate and 2,4,6-trimethyltetracosanoate, were detected in all strains. The frequency of chemotypes other than that of the type strain was 8% among the Finnish isolates. This variation should be recognized when confirmative identification of mycobacteria is based on thin-layer chromatography of glycolipid extracts.

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.

Capillary gas chromatographic analysis of mycolic acid cleavage products, cellular fatty acids, and alcohols of Mycobacterium xenopi

The fatty acids, alcohols, and mycolic acids of 26 strains of Mycobacterium xenopi were studied by capillary gas chromatography and thin-layer chromatography. All strains contained alpha-, keto-, and omega-carboxymycolates. The primary mycolic acid cleavage product was hexacosanoic acid. The fatty acid patterns and, especially, the presence of 2-docosanol are characteristic markers of M. xenopi.

Characterization of Mycobacterium paratuberculosis by gas-liquid and thin-layer chromatography and rapid demonstration of mycobactin dependence using radiometric methods

Thirty-six Mycobacterium paratuberculosis isolates of bovine, caprine, and ovine origins were evaluated by using gas-liquid chromatography (GLC), thin-layer chromatography (TLC), and BACTEC 7H12 Middlebrook TB medium (12A; Johnston Laboratories, Inc., Towson, Md.) in an effort to more rapidly differentiate this group of organisms from other mycobacteria. Bacterial suspensions (0.1 ml) were inoculated by syringe into 7H12 broth containing 2 micrograms of mycobactin P per ml and control broth without mycobactin P. Cultures were incubated at 37 degrees C and read daily with a BACTEC Model 301 (Johnston Laboratories). After 8 days of incubation, the growth index readings for the test broths containing mycobactin P were twice those of the control broths without mycobactin P. Sixty-five isolates of mycobacteria other than M. paratuberculosis were also examined. No difference was noted between the growth index readings of control and mycobactin-containing broths. Except for Mycobacterium avium-Mycobacterium intracellulare, TLC studies differentiated M. paratuberculosis from the other mycobacterial species tested. The GLC data reveal that all M. paratuberculosis isolates had a distinctive peak (14A) which was not found among M. avium-M. intracellulare complex organisms. These data indicate that 7H12 radiometric broth was able to rapidly demonstrate the mycobactin dependence of M. paratuberculosis and GLC and TLC procedures were capable of rapidly differentiating this organism from the other mycobacteria studied.

Evaluation of Gen-Probe DNA hybridization systems for the identification of Mycobacterium tuberculosis and Mycobacterium avium-intracellulare

The Gen-Probe DNA hybridization system, rapid diagnostic assays for the identification of Mycobacterium tuberculosis (MTB) complex and Mycobacterium avium-intracellulare (MAIC) complex, were evaluated. Designed to identify a primary mycobacterial isolate, the former correctly identified 91 of 92 MTB and all 27 non-MTB isolates and controls when compared with conventional identification methods for a sensitivity of 98.91% and specificity of 100%. The latter correctly identified 63 of 64 MAIC isolates and controls and 31 of 32 non-MAIC isolates and controls when compared with conventional identification methods for a sensitivity of 98.43% and a specificity of 96.87%. The one false positive noted with the MAIC probe was an MTB misidentified as an MAIC. The two false negatives noted above were subsequently shown to be contaminated. The tests are fast and easy to perform and interpret.

Analysis of mycolic acid cleavage products and cellular fatty acids of Mycobacterium species by capillary gas chromatography

After growth and experimental conditions were established, the mycolic acid cleavage products, constituent fatty acids, and alcohols of representative strains of Mycobacterium tuberculosis, M. smegmatis, M. fortuitum complex, M. kansasii, M. gordonae, and M. avium complex were determined by capillary gas chromatography. Reproducible cleavage of mycolic acid methyl esters to tetracosanoic (24:0) or hexacosanoic (26:0) acid methyl esters was achieved by heating the sample in a high-temperature muffle furnace. The major constituent fatty acids in all species were hexadecanoic (16:0) and octadecenoic (18:1 omega 9-c, oleic) acids. With the exception of M. gordonae, 10-methyloctadecanoic acid was found in all species; moreover, M. gordonae was the only species tested which contained 2-methyltetradecanoic acid. M. kansasii was characterized by the presence of 2,4-dimethyltetradecanoic acid, M. avium complex by 2-eicosanol, and M. tuberculosis by 26:0 mycolic acid cleavage product. The mycolic acid cleavage product in the other five species tested was 24:0. Although a limited number of strains and species were tested, preliminary results indicate that this gas chromatographic method can be used to characterize mycobacterial cultures by their mycolic acid cleavage products and constituent fatty acid and alcohol content.

Rapid and sensitive identification of Mycobacterium tuberculosis

The fatty acid constituents of 14 species of Mycobacterium (14 isolates) and one isolate each of Corynebacterium xerosis, Nocardia asteroides, and Streptomyces albus were examined with the purpose of distinguishing Mycobacterium tuberculosis from other acid-fast bacilli. Combined thin-layer chromatography (TLC) of methyl mycolates and gas-liquid chromatography (GLC) of shorter-chain fatty acid esters provided an unequivocal identification of M. tuberculosis in a matter of 2 to 3 days. The methodology included rapid and simplified procedures for methanolysis and extraction of bacterial lipids with equally facilitated GLC and TLC analyses. These studies were performed with 0.5 to 1.0 mg of dry bacterial cells (approximately 2.5 X 10(7) CFU). When applied to 100 unknown cultures, the methodology with combined TLC-GLC correctly identified all 49 of the M. tuberculosis-Mycobacterium bovis cultures and a variety of other mycobacterium taxa. It was also interesting to note that 28 of 39 (72%) of the nontuberculous mycobacteria were correctly identified. An additional five species were tentatively identified as belonging to either of two species (Mycobacterium malmoense, Mycobacterium terrae), but in all cases, the two species belonged to the same Runyon group. All six nonmycobacterial species were differentiated from the mycobacteria studied.

Influence of culture medium and incubation time on the fatty acid compositions of some rapid-growing mycobacteria as analysed by packed and capillary column gas chromatography

Cellular fatty acids of four rapid-growing mycobacterial species (Mycobacterium chelonei, M. fortuitum, M. phlei, and M. smegmatis) were analysed by packed and capillary column gas chromatography after one, three, four, six, eight, and twelve days of incubation on Löwenstein-Jensen and Sauton agar media. Variations in incubation time did not affect the chromatograms except in the case of twelve-day incubated M. smegmatis. Mycobacteria cultivated on Sauton agar medium contained more tuberculostearic and less oleic acid compared with Löwenstein-Jensen. For informative and reproducible analytical results, we recommend using a chemically defined culture medium and splitless injection on a capillary column capable of separating not only the methyl esters of the cellular fatty acids but also the diagnostically important secondary alcohols containing 18 and 20 carbon atoms.

Gas chromatographic fatty acid profiles for characterisation of mycobacteria: an interlaboratory methodological evaluation

Three species of mycobacteria were cultured and processed for cellular fatty acid analysis by capillary gas chromatography in three laboratories to study interlaboratory variations of the resulting chromatographic profiles. Largely consistent and characteristic fatty acid profiles were obtained, although there were minor quantitative variations in the patterns due to methodological differences (cultivation, hydrolysis, derivatization, gas chromatographic conditions etc.). The following points were important for achieving informative and reproducible results. A chemically defined growth medium (e.g., Proskauer-Beck) provides more consistent profiles than the lipid-rich Löwenstein-Jensen medium. Harvesting directly into the digesting solution (NaOH or HCl in methanol) followed by heating or autoclaving is a simple and reliable way of releasing fatty acids. Care should be taken to ensure reproducible detection of long-chain alcohols either by using acid methanolysis or including a base-wash step in the procedure following alkaline hydrolysis. The temperature of the gas chromatographic injector should be at least 325 degrees C. A capillary column of a minimum length of 10 m coated with a methyl silicone is adequate. Our results indicate the possibility of recommending a practical and reproducible gas chromatographic procedure for mycobacterial characterisation.

Rapid identification of mycobacteria using gas liquid chromatography

Methyl esters of fatty acids derived from 110 strains of previously identified mycobacteria representing 17 species and a group of unidentified rapid growers, were examined by gas-liquid-chromatography (GLC). Ten species had specific GLC profiles, which enabled accurate identification; but in 2 groups of species strains shared common profiles. M. bovis, and M. xenopi usually had specific profiles but one strain of each could not be distinguished from M. tuberculosis. The group comprising M. terrae, M. fortuitum, M. chelonei, M. flavescens and rapid growers were generally not well separated by GLC; however, 6 of 12 M. terrae strains, 2 of 3 M. flavescens, and all 5 M. fortuitum strains had specific profiles. Other strains of this group had only common peaks and by GLC were indistinguishable from each other. Using a table of specific and characteristic peaks, 34 of 54 (63%) recent isolates were correctly identified, and 18 (33%) were correctly allocated to groups sharing similar GLC profiles: only 2 isolates were wrongly identified. At present, GLC analysis provides easy and rapid identification of a majority of mycobacteria but cannot replace fully biochemical tests in the identification of medical mycobacteria.

The role of cell-wall associated lipids in the pathogenesis of lesions in experimental murine nocardiosis vs lesions produced by Mycobacterium fortuitum

The pulmonary pathogens, Nocardia asteroides and Mycobacterium fortuitum classically produce a markedly different tissue response ranging from the acute suppurative lesion of nocardiosis to the granulomatous disease produced by the Mycobacterium. Both organisms have similar cell-wall associated lipids which have been chemically characterized as types of saturated and unsaturated fatty acids. Earlier studies of virulence factors from M. tuberculosis and other Mycobacteria have shown that much of the host response is due to lipid constituency of the organism cell wall. In order to determine that contribution which the cell-wall associated lipids make in the pathogenesis of nocardiosis produced by N. asteroides and mycobacteriosis due to M. fortuitum, separate lipid fractions were obtained using the Anderson extraction technique as modified by Asselineau (Asselineau, J. 1966. The Bacterial Lipids. Hermann, Paris). These lipid fractions were injected into mice and the lesion development observed. Waxes A and D from the two organisms exhibited distinct differences in tissue response. Wax A from Nocardia produced a pronounced tissue response composed of multiple abscesses, macrophages, and reactive fibrous tissue. Wax A from Mycobacterium showed transient aggregations of polymorphonuclear leukocytes. Mycobacteria-derived wax D elicited a marked granulomatous response which persisted throughout the duration of the study, contrasting with a minimally acute inflammatory response to Nocardia-derived wax D. The phosphatide and soluble-fat fractions also showed aggressive lesions; however, these were similar for both organisms. These results indicate that the differences in tissue response elicited by lipids from N. asteroides and M. fortuitum may reside in wax fractions A and D.

Acidic methanolysis v. alkaline saponification in gas chromatographic characterization of mycobacteria: differentiation between Mycobacterium avium-intracellulare and Mycobacterium gastri

Mycobacterium avium-intracellulare and M.gastri were analyzed with capillary gas chromatography after each strain had been subjected to acidic methanolysis or to alkaline saponification followed by methylation. Prominent peaks of myristic, palmitoleic, palmitic, oleic, stearic and tuberculostearic acids were found in the chromatograms of both species, whereas 2-octadecanol and 2-eicosanol were detected only in M. avium-intracellulare. In initial runs, both of the derivatization principles yielded virtually identical chromatograms for a given strain. After repeated injections of extracts from alkaline saponification, however, the alcohol peaks showed pronounced tailing and finally almost disappeared from the chromatograms. This disadvantage, which was not observed when only acid methanolysis was used, could be overcome with trifluoroacetylation. Restored peak shape of the underivatized alcohols could be achieved by washing the cross-linked stationary phase in the capillary tubing with organic solvents. The study demonstrated the importance of conditions which enable separation of 2-octadecanol and 2-eicosanol when gas chromatography is used for species identification of mycobacteria.

Wild animal mycobacterial isolates. Characterization by cellular fatty acid composition and polar lipid patterns

Thirteen strains of mycobacteria isolated from deer and various species of wild birds were analysed by gas chromatography (GG) for cellular fatty acids and by thin-layer chromatography (TLG) for polar lipids. These strains were compared to reference strains of Mycobacterium avium, M. para tuberculosis and M. mal-moense. All the examined strains exhibited a generally similar fatty acid pattern characterized by relatively large amounts of hexadenca-noate (16:0), octadecenoate (18:1), octadecanoate (18:0) and 10-me-thyl-octadecanoate (tuberculostearic acid, 10-Me-18:0). Several additional acids were also generally present but in smaller amounts. By means of small but distinct differences in fatty acid composition, the wild animal isolates could be distinguished from both M. paratuber-culosis and M. malmoense but not from M. avium.

The TLG polar lipid patterns on the other hand separated the wild animal isolates into 2 distinct groups of complex and simple polar lipid composition which corresponded to the morphologically smooth and rough types, respectively. The complex patterns of the smooth strains were comparable to those of the M. avium serovars whereas both the rough wild animal isolates and all the M. paratuber-culosis strains showed a simple pattern of polar lipids.

Both fatty acid profiles and TLG polar lipid patterns support allocation of the wild animal isolates to the MAIS complex. Moreover, the 2 chemical techniques, particularly the GC procedure, are very useful for a more rapid and precise identification of the slow-growing wild animal mycobacterial isolates which have hitherto been characterized on basis of vague criteria.