Method of diagnosing pneumonia by detecting a volatile organic compound

A method of diagnosing an existing or developing acute pneumonia induced by a microorganism comprising:

• a) obtaining a respiratory air sample from a subject,
• b) detecting one or more volatile organic compound(s) in the respiratory air sample without culturing the respiratory air sample prior to the detecting, wherein the volatile organic compound is selected from the group consisting of 2-ethylacrolein, 2-methyl-2-butenal (Z), ethyl formate, ethyl isovalerate, isopentyl acetate, hydroxyacetone, 2-butanol, 2-methylbutyl 2-methylbutyrate, 2-methylbutyl isobutyrate, amyl isovalerate, ethyl 2-methylbutyrate, isoamyl butyrate, methyl 2-methylbutyrate, 1,10-undecadiene, 10-methyl-1-undecene, 1-decene, 1-nonene, 1-vinyl aziridine, mercaptoacetone, 3-phenylfuran, 3-(methylthio)propanal, o-hydroxybenzaldehyde, methyl propionate, vinyl butyrate, 2-acetyl-1,4,5,6-tetrahydropyridine, S-methyl thioacetate, 3-methyl-1-butanol, 3-(ethylthio)-propanal, 1-butanol, dimethyltrisulfide (DMTS), methyl methacrylate, and
• c) administering an effective amount of an antibiotic to the subject when the one or more volatile organic compound(s) in the sample are detected in the respiratory air sample.