The Antimicrobial Properties of Ascaris suum Pseudocoelomic Fluid and its Microbiome
Parasitic nematodes are common pathogens of agricultural animals where they live in close association with the host intestinal microbiota. This hostile environment presents challenges to worm health and longevity which are managed through the worm's innate immune system that includes the production of antimicrobial peptides (AMPs). The profile and significance of worm-derived AMPs is currently unknown; in addition to protecting the parasite from pathogen infection, worm-derived AMPs may also play a role in shaping the surrounding microbial community of the host including both commensals and invading bacterial pathogens. .
Ascaris suum is an excellent model parasite that can be readily collected from the intestines of pig at local abattoirs. Ascaris is large in size and amenable to both tissue-level dissection and body cavity fluid collection. In this study we exploit the experimental tractability of Ascaris to evaluate the antimicrobial properties of the pseudocoelomic fluid, and to identify an endogenous microbial community within the body cavity fluid.
Data to date highlight that Ascaris PCF displays bactericidal properties against the gram negative bacilli, Staphylococcus aureus and Bacillis subtilis. In contrast Ascaris PCF did not have any impact the gram positive bacterium, Staphylococcus epidermidis, or gram negative species,Escherichia coli; indeed Ascaris PCF appeared to act as a probiotic when in the presence of S. epidermis and E. coli enhancing growth of these two species. In addition, an endogenous PCF microbiota was observed following an overnight culture of Ascaris PCF in aerobic conditions. These data suggest the Ascaris PCF has both bactericidal and probiotic properties that appear to be species selective. The presence of an endogenous microbial community within the PCF offers an opportunity to dissect the dynamic interactions between the microbiome of the PCF and worm-derived AMPs, and how they might both impact on the diversity of commensals and pathogens within the host. Data generated in this project have the potential to uncover AMPs that have therapeutic potential against key pathogens of livestock. In addition, understanding the importance of nematode-derived AMPs to nematode survival may inform future parasite control options.