F-023. The Effects of Candida albicans Colonization on the Murine Microbiota

K. Mason, N. R. Falkowski, V. B. Young, J. Y. Kao, G. B. Huffnagle;
Univ. of Michigan, Ann Arbor, MI.

The human body’s indigenous microbiota is comprised of nearly 1014 microbes and the majority of these microbes are obligate anaerobes, hindering previous studies using classical culturing techniques. However, recent molecular approaches have allowed researchers to begin to look at the makeup of the gastrointestinal (GI) tract microbiota. Our objective was to examine the effect of Candida albicans colonization on changes in the bacterial microbiota populations of the GI tract. Terminal Restriction Fragment Length Polymorphism (T-RFLP) analysis was used to analyze the bacterial communities. This approach takes advantage of the differences in 16S rRNA genes to allow quantification of specific bacterial species within complex samples in a culture independent manner. Our first set of experiments was to determine the role that factors such as genetics, vendor source, and housing have on the microbiota. Intra-cage microbiota variation was minimal in mice of the same sex and age. However, there was a wider variation in microbiota composition between groups of mice in different cages. We also found that genetically identical mice (C57BL/6) from different vendors have different microbiota, as revealed by T-RFLP. In our second set of experiments, we analyzed the microbiota in mice treated for 5 days with cefoperazone, a broad spectrum antibiotic, in the drinking water, followed by a single oral gavage of Candida albicans. As expected, antibiotic treatment initially disrupts the “normal” microbiota but after 4 weeks, the T-RFLP patterns began to resemble that of untreated mice. In contrast, mice that were treated with antibiotics and low level colonized with C. albicans (1000 CFU/g cecum) had a significantly different microbiota than untreated, antibiotic only or Candida only treated mice. This difference was far greated than could be accounted for by cage-cage variation. Thus, while C. albicans appears to exert only a minor influence on bacterial populations in an established community in the gut, the presence of C. albicans can exert a significant influence on the bacterial communities in the GI tract during recolonization after antibiotics.