Identification of putative volatile biomarkers of canine leishmaniasis in dog's breath and hair employing a novel algorithm for automated chromatographic peak detection and matching

The analysis of the volatile compounds released by biological samples represents a promising approach for the non-invasive diagnosis of a disease. The present study, focused on a population of dogs infected with canine leishmaniasis, aimed to decipher the volatolomic profile associated with this disease in dogs, which represent the main animal reservoir for Leishmania pathogen transmission to humans. The volatiles emitted by the breath and hair of dogs were analysed employing the gas chromatography-mass spectrometry (GC-MS) technique. The acquired chromatograms were investigated using a novel algorithm developed in this study for automated chromatographic peak detection and matching in untargeted GC-MS analysis, which includes various steps that comprise noise reduction, m/z filtering, background subtraction, peak detection, peak matching, and generation of a peak table for compounds identification. The results revealed one tentative breath volatile biomarker and five tentative hair volatile biomarkers for the cutaneous form of the disease, which is characterised by skin ulcerations. Additionally, nine tentative breath volatile biomarkers and four tentative hair volatile biomarkers were found for the visceral form of the disease, which affects internal organs such as spleen, liver and bone marrow. All tentative biomarkers identified in this study were upregulated in cutaneous leishmaniasis, while in visceral leishmaniasis, all tentative biomarkers were upregulated in the breath and only one out of four in the hair. Only one compound (glyceryl monooleate) was identified as tentative volatile biomarker for both forms of the disease, in the hair of dogs.