The volatile metabolome of Klebsiella pneumoniae in human blood.

Klebsiella pneumoniae is an important cause of bloodstream infections in critically-ill patients, with mortality exceeding 50% for infections caused by antibiotic-resistant strains. Despite its importance as a bacteremia-causing agent, there is little known about the metabolism of K. pneumoniae during growth in pure human blood. Here, we comprehensively profile the volatile metabolites produced by K. pneumoniae during growth in human blood to approximately mid-exponential (7 h) and early stationary (12 h) phases using 2D gas chromatography-time-of-flight mass spectrometry (GC×GC-TOFMS). We identified 33 volatile molecules that were significantly more abundant in K. pneumoniae cultures relative to sterile blood, of which 22 were detected in cultures only. We identified nine molecules that have not previously been reported as K. pneumoniae-associated headspace volatiles, four of which we believe to be novel bacterial-associated volatiles. We also identified a set of 17 volatile molecules that discriminate between 7 h and 12 h K. pneumoniae cultures, indicating either growth phase or cell density-associated changes in the composition of headspace volatiles. Our analysis of the volatile molecules produced by K. pneumoniae during growth in human blood using GC×GC-TOFMS has doubled the number of volatiles reported for this organism in blood-containing media, and increased the total number of K. pneumoniae-associated volatiles by 20%. The volatile molecules produced by K. pneumoniae in blood may represent novel biomarkers for the diagnosis of bacteremia.