Affiliation:
1. Department of Microbiology and Molecular Genetics, UC Davis, Davis, California, USA
2. Departments of Biology and Microbiology & Immunology, Georgetown University, Washington, DC, USA
Abstract
ABSTRACT
Giardia lamblia
is the most frequently identified protozoan cause of intestinal infection. Over 200 million people are estimated to have acute or chronic giardiasis, with infection rates approaching 90% in areas where
Giardia
is endemic. Despite its significance in global health, the mechanisms of pathogenesis associated with giardiasis remain unclear, as the parasite neither produces a known toxin nor induces a robust inflammatory response.
Giardia
colonization and proliferation in the small intestine of the host may, however, disrupt the ecological homeostasis of gastrointestinal commensal microbes and contribute to diarrheal disease associated with giardiasis. To evaluate the impact of
Giardia
infection on the host microbiota, we used culture-independent methods to quantify shifts in the diversity of commensal microbes throughout the gastrointestinal tract in mice infected with
Giardia
. We discovered that
Giardia
's colonization of the small intestine causes a systemic dysbiosis of aerobic and anaerobic commensal bacteria. Specifically,
Giardia
colonization is typified by both expansions in aerobic
Proteobacteria
and decreases in anaerobic
Firmicutes
and
Melainabacteria
in the murine foregut and hindgut. Based on these shifts, we created a quantitative index of murine
Giardia
-induced microbial dysbiosis. This index increased at all gut regions during the duration of infection, including both the proximal small intestine and the colon. Giardiasis could be an ecological disease, and the observed dysbiosis may be mediated directly via the parasite's unique anaerobic fermentative metabolism or indirectly via parasite induction of gut inflammation. This systemic alteration of murine gut commensal diversity may be the cause or the consequence of inflammatory and metabolic changes throughout the gut. Shifts in the commensal microbiota may explain observed variations in giardiasis between hosts with respect to host pathology, degree of parasite colonization, infection initiation, and eventual clearance.
Funder
HHS | National Institutes of Health
Publisher
American Society for Microbiology
Subject
Infectious Diseases,Immunology,Microbiology,Parasitology
Cited by
95 articles.
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