Modulating the gut microbiota with a synthetic stool “MET-1”: protective effects in animal models of antibiotic associated colitis
Loading...
Authors
Martz, Sarah-Lynn
Date
2013-10-02
Type
thesis
Language
eng
Keyword
Salmonella enterica serovar Typhimurium , Antibiotic associated colitis , Synthetic stool , Clostridium difficile
Alternative Title
Abstract
Antibiotics disrupt the normal balance of the gut microbiota and may subsequently reduce colonization resistance, allowing pathogenic bacteria to colonize and cause disease. By re-introducing normal microbiota from a donor, colonization resistance can be restored. Based on this premise, a complex mixture, “microbial ecosystem therapeutic-1” (MET-1) containing 33 strains of commensal bacteria was derived from the stool of a healthy human donor. This gut microbial ecosystem has been successfully used to treat two patients infected with C. difficile, but mechanisms of action of the beneficial effects of MET-1 were undefined. An infectious antibiotic-associated mouse model of S. typhimurium and a germ free mouse model of C. difficile infection were utilized to determine the therapeutic effect of MET-1. In the S. typhimurium model, female C57BL/6 mice were pretreated with oral streptomycin prior to receiving MET-1 or vehicle control. When S. typhimurium infected mice were pretreated with MET-1, weight loss was attenuated (-3.5% vs. -6.8%; p<0.05). Serum cytokine levels of TNF-α, MIP-1β, IL-3 and GM-CSF were all significantly reduced. The S. typhimurium bacterial loads in the spleen were decreased in mice pretreated with MET-1 (9190 CFU/g vs. 25,438 CFU/g; p<0.05). Verified using a time-kill assay, MET-1 was bactericidal against S. typhimurium. These results showed that MET-1 could have attenuated the infection by inhibiting the growth of S. typhimurium. Germ-free, female Swiss Webster mice were pretreated with MET-1 or vehicle control prior to infection with C. difficile strain 027. In infected mice that were pretreated with MET-1 weight loss was attenuated, (-2.43% vs. -13.35%; p<0.05) and serum cytokine levels of TNF-α, IL-1β, IL-6, GM-CSF, MCP-1, MIP-1α and MIP-1β were all significantly reduced. The C. difficile bacterial loads in the cecum were reduced in mice pretreated with MET-1 (1.1x106 CFU/g vs. 1.9x108 CFU/g; p<0.05). In this model MET-1 was able to restore colonization resistance and therefore attenuate the C. difficile infection. Therefore, using a complex microbial community could restore colonization resistance against two different pathogens, S. typhimurium and C. difficile. In the future, MET-1 could be used as a prophylactic in conjunction with antibiotics to ensure colonization resistance is maintained against pathogenic bacteria.
Description
Thesis (Master, Microbiology & Immunology) -- Queen's University, 2013-09-29 21:18:18.966
Citation
Publisher
License
This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.