Volatile organic compounds produced by thermophilic and non-thermophilic Campylobacter spp.: Influence of growth phase and nutrient composition

Abstract

Bacteria produce a plethora of volatile organic compounds (VOCs) into the atmosphere as a means of interacting with their habitats, as well as for intra- and interkingdom communication, and to survive and thrive in nature and inside their hosts. Campylobacter, which is commonly found in poultry and ruminants, has demonstrated remarkable endurance in aquatic settings, making it one of the world’s most hazardous foodborne pathogens that kill thousands of humans every year. In the present work, the VOCs released by both thermophilic (C. jejuni, C. coli, and C. lari) and non-thermophilic (C. fetus) Campylobacter of clinical significance, which were influenced by nutrient composition (media) and growth phase, were profiled using an active sampling approach, with active charcoal adsorbent and gas chromatography-mass spectrometry. Alcohols and ketones were detected only in the thermophilic Campylobacter strains, C. jejuni subsp. jejuni (1-heptadecanol; 1, 8-nonadien-3-ol; 3, 7, 11-trimethyl-3-dodecanol; 1s, 4R, 7R, 11R-1, 3, 4, 7-tetramethyltricyclo [5.3.1.0(4, 11)] undec-2-en-8-one; and isophorone), C. coli (isophorone and 3, 5-bis(1, 1-dimethylethyl)-phenol), and C. lari (3, 7, 11-trimethyl-3-dodecanol and 1s, 4R, 7R, 11R-1, 3, 4, 7-tetramethyltricyclo [5.3.1.0(4, 11)] undec-2-en-8-one) between early stationary and stationary growth phases. The non-thermophilic C. fetus produced only a range of unidentified compounds that need to be investigated further in the future. The results from the principal component analysis showed distinctive clustering of VOC markers between the four bacteria taxa and within the strains of C. jejuni, including distinguishable groupings of VOCs throughout the growth phase of each bacterium and between different culture media. This demonstrates the influence of bacterial growth and media composition on the volatilome of the studied Campylobacter spp. Overall, the VOC profiling of these foodborne pathogens, under influencing factors of growth phase and media, paves the way for future rapid identification of Campylobacter spp. in food matrices.