Candida albicans is a commensal fungus that resides in the gastrointestinal (GI) tract of over 60% of adults. Commensalism is maintained by the intact epithelial barrier, a functional host immune response, and competition with the local bacterial microbiota. However, if these mechanisms are disrupted, C. albicans can increase in number, escape the gut, and disseminate via the blood, resulting in systemic infection and sepsis. Even with antifungal intervention, mortality is as high as 47%, and a novel strategy to combat these infections is needed.
We hypothesise that there are bacteria within the human GI tract that are antagonistic against C. albicans. These antagonistic bacteria could form the basis of a microbial therapeutic – a defined, standardised, and clinically-tested microbial community – that could be administered to at-risk individuals to clear the resident C. albicans from the gut, thereby preventing infection by removing the source.
To identify GI bacteria that are antagonistic towards C. albicans, we are collecting faecal samples from fifty healthy adult donors. An in vitro colon model is being used to assess whether the faecal samples can kill C. albicans, by culturing C. albicans in the presence of a homogenate of each donor sample and measuring colony forming units over 48 h. The bacterial composition of the faecal samples will be assessed by 16S rRNA gene sequencing. Multivariate statistical analyses will then be carried out to identify the specific bacterial species or taxa that are statistically significantly associated with antagonism – i.e., the in vitro killing of C. albicans.
Results obtained from the study thus far will be presented, alongside data from a pilot study involving just six donors that has already indicated the validity of this approach. In future, the bacteria identified in our study will be isolated and cultured, and their ability to clear C. albicans from an in vitro colon model and an ex vivo gut organoid model will be tested.