Abstract
BackgroundRecent evidence suggests that the commensal microbes act as a barrier against invading pathogens and enteric infections are the consequences of multi-layered interactions among commensals, pathogens, and the host intestinal tissue. However, it remains unclear how perturbations of the gut microbiota compromise host infection resistance, especially through changes at species and metabolite levels.ResultsHere, we illustrate how Bacteroides vulgatus, a dominant species of the Bacteroidetes phylum in mouse intestine, suppresses infection by Vibrio cholerae, an important human pathogen. Clindamycin (CL) is an antibiotic that selectively kills anaerobic bacteria, and accordingly Bacteroidetes are completely eradicated from CL-treated mouse intestines. The Bacteroidetes-depleted adult mice developed severe cholera-like symptoms, when infected with V. cholerae. Germ-free mice mono-associated with B. vulgatus became resistant to V. cholerae infection. Levels of V. cholerae growth-inhibitory metabolites including short-chain fatty acids plummeted upon CL treatment, while levels of compounds that enhance V. cholerae proliferation were elevated. Furthermore, the intestinal colonization process of V. cholerae was well-simulated in CL-treated adult mice.ConclusionsOverall, we provide insights into how a symbiotic microbe and a pathogenic intruder interact inside host intestine. We identified B. vulgatus as an indigenous microbial species that can suppress intestinal infection. Our results also demonstrate that commensal-derived metabolites are a critical determinant for host resistance against V. cholerae infection, and that CL pretreatment of adult mice generates a simple yet useful model of cholera infection.
Highlights
Recent evidence suggests that the commensal microbes act as a barrier against invading pathogens and enteric infections are the consequences of multi-layered interactions among commensals, pathogens, and the host intestinal tissue
In order to observe the effects of gut microbiota compositional changes on host infection resistance under diverse experimental conditions, we treated adult C57BL/6 specific pathogen-free (SPF) mice (8 weeks of age) with three different antibiotics that have a distinct mode of bacterial killing; streptomycin (SM), vancomycin (VAN), and clindamycin (CL)
Since CL would not be much left in the feces discharged from the CL-treated mice, our results demonstrate that altered gut microbiota composition induced by CL treatment is directly responsible for rendering the murine host more susceptible to V. cholerae infection
Summary
Recent evidence suggests that the commensal microbes act as a barrier against invading pathogens and enteric infections are the consequences of multi-layered interactions among commensals, pathogens, and the host intestinal tissue. It remains unclear how perturbations of the gut microbiota compromise host infection resistance, especially through changes at species and metabolite levels. Microbiota-intrinsic factors such as interactions between the gut-residing species serve as the primary determinant of community composition. Such interactions include interbacterial niche competition [9] and secretion of antimicrobial substances [10]. Compositional shift induced by an external factor may, in turn, modulate the host immune response via production of specific metabolites [8]
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