Detection of 2-eicosanol by gas chromatography-mass spectrometry in sputa from patients with pulmonary mycobacterial infections

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.

Modern laboratory diagnosis of tuberculosis

One-third of the global population is believed to be infected with bacteria of the Mycobacterium tuberculosis complex, the causative agent of tuberculosis. More than 8 million new cases of tuberculosis occur annually leading to 2 million deaths. Mortality is particularly high in those coinfected with HIV and where the bacteria are multiple-drug-resistant strains--ie, strains resistant to at least isoniazid and rifampicin. Early diagnosis of tuberculosis and drug resistance improves survival and by identifying infectious cases promotes contact tracing, implementation of institutional cross-infection procedures, and other public-health actions. This review addresses significant advances made in the diagnosis of infection, clinical disease, and drug resistance over the past decade. It proposes operational criteria for a modern diagnostic service in the UK (as a model of a low-incidence country) and explores some of the economic issues surrounding the use of these techniques.

Study of the microbial aggregation in Mycobacterium using image analysis and electron microscopy

Cellular aggregation, which occurs in both prokaryotes and eukaryotes, is controlled by the hydrophobicity as well as the electrokinetic potential of the cell surface and substratum. It is known that the Mycobacterium genus form aggregates, but the influence of sugar on the cellular aggregation has not been reported for this genus. The mutant strain Mycobacterium sp. MB-3683 that transforms sterol to androstenedione (AD), a steroidal precursor used by the pharmaceutical industries, was employed in this study. This strain was cultivated in a synthetic medium on three sugars (glycerol, glucose and fructose) at different concentrations, and at 144 h microbial growth, cellular aggregation, hydrophobicity, lipid content, fatty acid composition, and width of cellular walls were measured. It was observed that at different sugar concentrations, similar growth and pH were obtained. However, in fructose, the aggregation level was significantly high, followed by glycerol and glucose (fructose < glycerol < glucose). These results were confirmed using electron microscopy and the aggregate area quantified by image analysis. Hydrophobicity was the highest in fructose and the lowest in glucose. The total lipids, in contrast to cellular hydrophobicity, were higher in glucose than glycerol. Although, the hydrophilic-lipophilic balance (HLB) of principal fatty acids isolated was similar regardless of sugar used. In glycerol and fructose, the paraffins were observed, which are responsible for the high cellular hydrophobicity detected above. The width of cell wall of the organisms grown on glucose and fructose was similar, but in glycerol the walls were very thin. There is a correspondence between cell wall width and lipid content.

Diagnostic test needs for evaluating antituberculosis vaccines

To aid in the evaluation of preexposure and postinfection vaccines to prevent tuberculosis, diagnostic tests are needed that can clearly distinguish immunologic protection from vaccine failure in a timely manner. The currently available tests to detect infected persons (tuberculin skin-test) and confirm active disease (conventional culture methods) have limitations in specificity, sensitivity, or timeliness. Research to identify (1) surrogate markers of infection, disease, or protection and (2) stage-specific antigens or immune responses holds some promise for the development of new tests that can distinguish the various outcomes of an infection or a vaccination.

Use of gas chromatography-ion trap tandem mass spectrometry for the detection and characterization of microorganisms in complex samples

Gas chromatography-mass spectrometry (GC-MS) can be applied to detect and characterize microorganisms in clinical and environmental samples, and microbial contaminants in biotechnological production cultures. With this approach, unique microbial monomeric compounds, known as chemical markers, are used as analytes. In the present article, two GC-MS-based techniques, viz. GC-ion trap tandem MS (GC-MS-MS) and conventional quadrupole GC-MS used in the selected ion monitoring mode, were compared regarding their ability to detect 3-hydroxy fatty acids, muramic acid, and ergosterol (markers for endotoxin, peptidoglycan, and fungal biomass, respectively) in complex matrices. When using GC-MS-MS, daughter ion spectra were obtained for all markers present in amounts close to the detection limit of the GC-MS. Ion-trap GC-MS-MS shows great promise as a chemical marker analysis technique for application in clinical diagnosis, occupational and public health care, and biotechnology.

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.

Determination of microbial chemical markers by gas chromatography-mass spectrometry--potential for diagnosis and studies on metabolism in situ. Review article

Different strategies for the application of gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS) in medical microbiology research are discussed. GC can be used to determine specific microbial monomeric constituents and metabolites, so-called chemical markers, in cultures of microorganisms; in particular, analysis of cellular fatty acids has proven useful for species characterization and identification. GC-MS can be applied to study chemical markers directly in complex environmental samples, as exemplified by the analysis of airborne organic material as regards muramic acid (marker of peptidoglycan), 3-hydroxy acids (endotoxins), and ergosterol (fungal biomass). This methodological approach represents an alternative to various biological assays for characterization of airborne microbial structures, and forms a firm basis for correlating inhalation of such structures and development of symptoms. Direct GC-MS analysis of clinical samples provides possibilities for diagnosis (here exemplified by chiral separation of urine D- and L-arabinitol in disseminated candidiasis) and insight into microbial metabolism in the infected host (exemplified by observed indications of mycobacterial build-up of mycolic acids in vivo), with implications for drug development. Continued developments in MS technology will allow rapid advances to be made in GC-MS research in microbiology.