IDSA 2011: New Insights into the Human Microbiome, Part III

The final presenter in the press conference on the human microbiome at the annual meeting of the Infectious Diseases Society of America annual meeting was Mahmoud Ghannoum, PhD, director of the Center for Medical Mycology at the University Hospitals Case Medical Center and Case Western Reserve University. Ghannoum also presented his results to the entire meeting as a featured oral abstract. (Click here the read the first part and here to read the second part of this article.)

The Contested Mycobiome

Ghannoum explained that the purpose of his study was to look at the relationship between different elements of the oral microbiota in HIV patients. He and his colleagues characterized the core oral mycobiome (COM) and bacteriome (COB) in 12 patients with HIV and 12 healthy controls. The data showed that the same 14 genera constituted the COB in both groups and that there was no significant difference between the COB of subjects with or without HIV.

Analysis of the COM found that subjects with HIV had Candida, Penicillium, Alternaria, Epicoccum and Trichosporon, while the healthy controls had Candida, Penicillium, Pichia, Cladosporium, and Fusarium. Further analysis found that the decreased colonization by Pichia in the HIV subjects coincides with an increase in Candida, suggesting an antagonistic relationship between the two fungi.

To test the relationship between Pichia and Candida, the researchers introduced Pichia to Candida biofilms with Penicillium as a control. They found that the biofilms formed in the presence of Pichia were significantly disrupted and thinner. The newly established understanding that Pichia and Candida are mutually antagonistic could be used to develop novel methods of managing oral candidiasis in patients who have HIV or are otherwise immunocompromised.

Relman noted that one takeaway from the experiment is that the human microbiome is not just a random collection of organisms. The organisms present are there for a purpose and recognize and interact with each other—and these interactions can be exploited to help improve human health.