Variation in volatile organic compounds emitted by Campylobacter jejuni and Campylobacter spp. under different growth conditions / Filipe Magnum Silva Dos Santos

Filipe Magnum Silva, Dos Santos (2022) Variation in volatile organic compounds emitted by Campylobacter jejuni and Campylobacter spp. under different growth conditions / Filipe Magnum Silva Dos Santos. Masters thesis, Universiti Malaya.

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Abstract

Campylobacter jejuni subsp. jejuni is acknowledged worldwide as the leading cause of gastroenteritis in humans. A low dose of bacterial cells is able to develop the illness known as campylobacteriosis. The symptoms are usually mild and self-limiting, however, the sequalae may be severe, due to neurological disorders such as Guillain–Barré Syndrome, that is an autoimmune disease characterised by weakness of limbs and paralysis. Consumption of poultry products, mainly chicken, have been known as the main route of transmission. Moreover, the challenges for laboratorial isolation and identification of Campylobacter spp. represent an unavoidable risk factor that has urged for the development of new methods and technology for Campylobacter infection that is easy to operate, highly specific, and rapid if not real-time output at a low operational cost. Some studies have proposed volatile organic compounds (VOCs) fingerprinting as a potential alternative to screen for the presence of VOCs emitted by bacteria. However, subjected to the type of media, the growth phase and the presence of other competitive pathogens, the VOCs produced by a particular bacterial species could vary considerably. In this study, the emission of volatiles of C. jejuni and other Campylobacter spp., considering all the beforementioned variables, was investigated. Active sampling using an activated coconut charcoal sorbent tube was used for adsorbing the VOCs of C. jejuni using different culture media, different incubation periods, and in the presence of other bacterial species. Samples with the volatiles desorbed in carbon disulphide were analysed through gas chromatography and mass spectrometry (GC-MS) and the dataset was subjected to multivariate evaluation via principal component analysis (PCA). Several volatiles were identified in this study, including alcohols, ketones, and phenols, that were produced during the growth of the bacteria. The study showed that C. jejuni produced the putative VOCs: 1,8-nonadien-3-ol, 3,7,11-trimethyl-3-dodecanol, 1-heptadecanol, isophorone, and 1s,4R,7R,11R-1,3,4,7-tetramethyltricyclo [5.3.1.0(4,11)] undec-2-en-8-one. The score plot of PCA demonstrated that the profile of VOC-markers emitted by different strains of C. jejuni, as well as other major Campylobacter spp. varied according to the growth phase. Also, the VOC variation of C. jejuni strains cultivated in different culture media was evidenced by the multivariate analysis tool. The volatilome profile uncovered in this study by means of solvent desorption technique laid an essential data for the advances of screening the pathogen in food matrices with high specificity, sensitivity and in a real-time way.

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