The isolation of novel Lachnospiraceae strains and the evaluation of their potential roles in colonization resistance against Clostridium difficile
Year: 2014
Type: dissertation
Abstract: Background: Antibiotic disruption of the gastrointestinal tract's indigenous microbiota can lead to one of the most common nosocomial infections, Clostridium difficile, which has an annual cost exceeding $4.8 billion dollars.The gut's unperturbed microbiota endow a protective effect against potential pathogens, inducing colonization resistance.Recent studies have found that mice resistant to C. difficile colonization, compared to those susceptible to C. difficile, have higher levels of microbes in the Firmicutes phylum, especially those of the Lachnospiraceae family.Another study showed that an isolate, Lachnospiraceae D4, which is closely related to Clostridium clostridioforme in 16S rRNA gene sequence, was able to restore partial colonization resistance to C. difficile in a germfree mouse.This study evaluates whether 23 Lachnospiraceae isolates can directly inhibit C. difficile and whether they have bile salt hydrolase and/or 7αdehydroxylase activity, which may affect C. difficile germination and growth.Methods: Lachnospiraceae isolates were obtained from C57BL/6 mouse cecal content, cecal tissue and feces then screened via a plate wash PCR procedure using Lachnospiraceae-specific primers.Direct inhibition of C. difficile by Lachnospiraceae isolates and communities was evaluated using an overlay plate technique.The presence of bile salt hydrolase was assessed in vitro using a plate assay and the presence 7α-dehydroxylase activity was assessed by PCR with baiCD-specific primers. Results:We successfully isolated 20 Lachnospiraceae isolates. Together with 3Lachnospiraceae isolates, including Lachnospiraceae D4, from Reeves, et al. none were able to directly inhibit C. difficile growth either through cell cultures or supernatants.However, we found 3 Lachnospiraceae isolates with bile salt hydrolase activity and 4 with 7α-dehydroxylase activity.Conclusions: If Lachnospiraceae are able to resist C. difficile colonization in the gastrointestinal tract, it is unlikely through direct inhibition.It is possible that by participating in varying points in the pathway of converting conjugated primary bile acids to secondary primary bile acids, a community of Lachnospiraceae can work together to restore colonization resistance against C. difficile.This aids in the development of probiotics against C. difficile infection.
Author: Diane Wang
Language: English
Subfield: Infectious Diseases
Field: Medicine
Domain: Health Sciences
Open Access status: green
Funder: National Institutes of Health
OpenAlex ID: W199618008