Ascaris suum interacts with host microbes and acquires its own microbiome

Abstract text

Introduction

Ascariasis is amongst the most prevalent soil-transmitted helminth infections in humans and pigs. In addition to modulating the host immune system, Ascaris resides in the microbial environment of the intestine and Ascaris infections are associated with alterations in the host microbiome. Additionally, Ascaris possesses its own intestine from which bacteria can be cultured. Despite the close association between intestinal nematodes and microbes, little is currently known about how nematodes contend with, or benefit from, their microbial neighbors and even less is known about the parasite"s own microbiome.

Objectives

The objectives of this work were to characterize antimicrobial strategies of helminths and to understand the elucidate the parasite microbiome and its interplay with the microbiome of its host.

Materials & Methods

Antimicrobial activities were assessed by harvesting excreted and secreted products (ESPs) of Ascaris suum and employing ESPs in various antimicrobial assays. Furthermore, ESPs were assessed by mass spectrometry. The Ascaris microbiome and the microbiome of its host were assessed by sequencing of the 16S rRNA gene in samples obtained from infected pigs.

Results

A. suum ESPs were found to possess various components with known and predicted antimicrobial activities. These products also reduced bacterial growth and disrupted biofilm formation in vitro. Furthermore, ESPs were also found to agglutinate bacteria. The A. suum microbiome was found to be derived, but distinct from, the microbiome of its host. In particular, dominant bacteria present at the site of infection appear to drive microbiome composition of the worm.

Conclusion

Our work presents a first look at the parasite microbiome while elucidating different antimicrobial strategies of Ascaris worms. These findings suggest that A. suum may selectively acquire microbes from their immediate surroundings.