Background:
There remains a need for techniques that improve the sensitive detection of viablePlasmodium falciparum as part of diagnosis and therapeutic monitoring in clinical studiesand usual-care management of malaria infections. A non-invasive breath test based on P.falciparum-associated specific volatile organic compounds (VOCs) could fill this gap andprovide insights into parasite metabolism and pathogenicity. The aim of this study was todetermine whether VOCs are present in the headspace above in vitro P. falciparum cultures.
Methods:
A novel, custom-designed apparatus was developed to enable efficient headspace sampling ofinfected and non-infected cultures. Conditions were optimized to support cultures of highparasitaemia (>20%) to improve the potential detection of parasite-specific VOCs. A numberof techniques for VOC analysis were investigated including solid phase micro-extractionusing two different polarity fibres, and purge and trap/thermal desorption, each coupled togas chromatography-mass spectrometry. Each experiment and analysis method wasperformed at least on two occasions. VOCs were identified by comparing their mass spectraagainst commercial mass spectral libraries.
Results:
No unique malarial-specific VOCs could be detected relative to those in the control red bloodcell cultures. This could reflect sequestration of VOCs into cell membranes and/or culturemedia but solvent extractions of supernatants and cell lysates using hexane, dichloromethaneand ethyl acetate also showed no obvious difference compared to control non-parasitizedcultures.
Conclusions:
Future in vivo studies analysing the breath of patients with severe malaria who are harbouringa parasite biomass that is significantly greater than achievable in vitro may yet reveal specificclinically-useful volatile chemical biomarkers.
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