Production of volatile organic compounds by mycobacteria

Abstract

The need for improved rapid diagnostic tests for tuberculosis disease has prompted interest in the volatile organic compounds (VOCs) emitted by Mycobacterium tuberculosis complex bacteria. We have investigated VOCs emitted by Mycobacterium bovis BCG grown on Lowenstein-Jensen media using selected ion flow tube mass spectrometry and thermal desorption-gas chromatography-mass spectrometry. Compounds observed included dimethyl sulphide, 3-methyl-1-butanol, 2-methyl-1-propanol, butanone, 2-methyl-1-butanol, methyl 2-methylbutanoate, 2-phenylethanol and hydrogen sulphide. Changes in levels of acetaldehyde, methanol and ammonia were also observed. The compounds identified are not unique to M. bovis BCG, and further studies are needed to validate their diagnostic value. Investigations using an ultra-rapid gas chromatograph with a surface acoustic wave sensor (zNose) demonstrated the presence of 2-phenylethanol (PEA) in the headspace of cultures of M. bovis BCG and Mycobacterium smegmatis, when grown on Lowenstein-Jensen supplemented with glycerol. PEA is a reversible inhibitor of DNA synthesis. It is used during selective isolation of gram-positive bacteria and may also be used to inhibit mycobacterial growth. PEA production was observed to be dependent on growth of mycobacteria. Further study is required to elucidate the metabolic pathways involved and assess whether this compound is produced during in vivo growth of mycobacteria.

Use of fecal volatile organic compound analysis to discriminate between non-vaccinated and BCG—Vaccinated cattle prior to and after Mycobacterium bovis challenge

“…Dimethyl sulfide has been previously reported in the literature as a compound associated with M . bovis cultures [58]. Eight of our tentatively identified compounds have not been previously reported in our prior studies or elsewhere.…”

“…Potential sources, and cellular, biological or metabolic functions associated with each tentatively identified compound were explored using KEGG, HMDB, and literature searches [32, 38, 53–55, 58–77] (Tables 6 and 7). Extensive metabolic information relative to M .…”

The Measurement of Ammonia in Human Breath and its Potential in Clinical Diagnostics

“…Ammonia, along with other VOCs could be considered for the diagnosis of tuberculosis (McNerney et al, 2012). The likelihood of VOC analysis being used to diagnose any inflammatory disease is low as these claims are not widely supported in the literature.…”

A novel pathway producing dimethylsulphide in bacteria is widespread in soil environments

“…It is known that some mycobacteria that contain mddA produce DMS, including M. bovis BCG 19 , but no soil-dwelling Bradyrhizobium or cyanobacteria, have previously been reported to produce DMS. We found that B. diazoefficiens USDA 110 and Cyanothece sp.…”