Volatile organic compounds emitted by pseudomonas aeruginosa and aspergillus fumigatus mono-cultures and in co-culture

Abstract

Volatile Organic Compounds (VOCs) analysis in exhaled breath is proposed as a non-invasive method to detect respiratory infections in cystic fibrosis (CF) patients. Since polymicrobial infections are increasingly common, we assessed whether fingerprints of VOCs emitted by mono-cultures of Pseudomonas aeruginosa (PA) and mono-cultures of Aspergillus fumigatus (AF) are consistent in a polymicrobial environment. Mono-cultures of PA (strain ATCC 27853), mono-cultures of AF (clinical isolate), and co-cultures of PA and AF were studied. Headspace samples were taken at 16, 24 and 48 hours after inoculation. VOCs in the headspace of the cultures were identified by Gas Chromatography – Mass Spectrometry. Multivariate analysis by Partial Least Squares Discriminant Analysis (PLS-DA) was used to identify unique VOC fingerprints for the presence of PA, AF or both. We identified VOC fingerprints consisting of 104 different compounds in each experimental setting. PLS-DA analysis was able to identify distinct VOC profiles for each of the monocultures and for the co-culture. Within each culture type, there is a large variation in the VOCs detected over time. Forty eight hours after inoculation, methyl thiolacetate is prominent and discriminating in PA cultures, 8-nonen-2-one in AF cultures and 2-nonanone in co-cultures. We can identify specific VOC fingerprints for PA and AF monocultures and co-cultures in vitro. This study shows that VOC fingerprints are time-dependent and that the fingerprints of PA and AF in mono-cultures are different from the VOC fingerprint in co-cultures, complicating the in vivo determination of micro-organisms when only based on VOC patterns.