Discrimination of Chemical Profiles of Some Bacterial Species by Analyzing Culture Headspace Air Samples Using TD-GC/MS

In an attempt to discriminate and identify several bacterial species, headspace air samples above a series of bacterial cultures were interrogated using a TD-GC/MS system. Three microorganism strains with relatively low pathogenic character – Escherichia coli, Bacillus subtilis and Staphylococcus aureus – were investigated during a period of 72 hours from the inoculation. Air samples with a volume of 1 L each were collected from the headspace above the bacterial cultures in agar growth medium of a 5 cm3 volume kept in 30 cm3 glass vials, in Tenax-Carbograph desorption tubes, by using a custom-built sampling unit based upon a portable air sampling pump. One sample was taken for each of the 10 different cultures of a bacterial strain, at 24, 48 and 72 hours from the incubation. The adsorption tubes were analyzed using the TD-GC/MS system and the resulting datasets – chromatograms and associated mass spectra – were used to produce a qualitative insight into the chemical profile of the headspace air above the bacterial cultures. Analysis by TD-GC/MS indicated that the chemical profile of the headspace air samples was complex and changed during the three days monitoring period; also, there appeared to be a series of chemicals specific to individual species of microorganisms.