Burkholderia pseudomallei is an emerging pathogen that causes
melioidosis, a serious and potentially fatal disease which requires prolonged
antibiotics to prevent relapse. However, diagnosis of
melioidosis can be difficult, especially in culture-negative cases. While metabolomics represents an uprising tool for studying
infectious diseases, there were no reports on its applications to B. pseudomallei. To search for potential specific
biomarkers, we compared the metabolomics profiles of culture supernatants of B. pseudomallei (15 strains), B. thailandensis (3 strains), B. cepacia complex (14 strains), P. aeruginosa (4 strains) and E. coli (3 strains), using ultra-high performance liquid chromatography-electrospray ionization-quadruple time-of-flight mass spectrometry (UHPLC-ESI-Q-TOF-MS). Multi- and univariate analyses were used to identify specific metabolites in B. pseudomallei.
RESULTS: Principal component and partial-least squares discrimination analysis readily distinguished the metabolomes between B. pseudomallei and other bacterial species. Using multi-variate and univariate analysis, eight metabolites with significantly higher levels in B. pseudomallei were identified. Three of the eight metabolites were identified by MS/MS, while five metabolites were unidentified against database matching, suggesting that they may be potentially novel compounds. One
metabolite, m/z 144.048, was identified as
4-methyl-5-thiazoleethanol, a degradation product of
thiamine (
vitamin B1), with molecular formula C6H9NOS by database searches and confirmed by MS/MS using commercially available authentic chemical standard. Two metabolites, m/z 512.282 and m/z 542.2921, were identified as tetrapeptides, Ile-His-
Lys-Asp with molecular formula C22H37N7O7 and
Pro-Arg-Arg-Asn with molecular formula C21H39N11O6, respectively. To investigate the high levels of
4-methyl-5-thiazoleethanol in B. pseudomallei, we compared the
thiamine degradation pathways encoded in genomes of B. pseudomallei and B. thailandensis. While both B. pseudomallei and B. thailandensis possess
thiaminase I which catalyzes degradation of
thiamine to
4-methyl-5-thiazoleethanol, thiM, which encodes
hydroxyethylthiazole kinase responsible for degradation of
4-methyl-5-thiazoleethanol, is present and expressed in B. thailandensis as detected by PCR/RT-PCR, but absent or not expressed in all B. pseudomallei strains. This suggests that the high
4-methyl-5-thiazoleethanol level in B. pseudomallei is likely due to the absence of
hydroxyethylthiazole kinase and hence reduced downstream degradation.
CONCLUSION: