Clinical and Genotypic Differences of Infectious vs. Colonizing Isolates of Candida albicans

Beth Klein
Carthage College

Beth Klein1,2, Brian Chow¹, Jennifer Meece², Jennifer Anderson2
¹Center for Clinical Epidemiology & Population Health, ²Integrated Research and Development Laboratory

Research area:  Integrated Research and Development Laboratory and Epidemiology

Background: Candidiasis, infection caused by Candida species yeast, is a prevalent and increasingly problematic concern, particularly in the immunocompromised host. Candida albicans causes the vast majority of candidiasis, and is more successful as a pathogen than other Candida species because of the high adaptability and variability of its genome. This study examined differences in clinical characteristics and treatment based on the apparent pathogenicity of the isolate, and genetic differences between invasive (infectious) and colonizing (non-infectious) C. albicans isolates. 

Methods: Data from 635 patients with positive C. albicans isolates were abstracted and analyzed to identify clinical and treatment indicators of infection. Records between January 2000 and May 2015 were selected randomly and stratified to include 100 isolates from blood cultures and all isolates from other sterile sites (e.g. cerebrospinal fluid). Records of all patients with isolates from May to July 2015 were abstracted and isolates genotyped for 7 housekeeping genes via Sanger Sequencing.

Results: Of the 257 infectious and 378 colonizing isolates reviewed, there were significant differences based on specimen type, antifungal treatment and duration, prior C. albicans infection, and absolute neutrophil count. Antifungal choice was significantly different between infectious and colonizing isolates, and infectious isolates were treated more frequently (86%) than colonizing isolates (14%). Colonizing isolates are over-treated, likely as a preventative measure. Forty-two positive C. albicans isolates from May to July 2015 were subject to DNA extraction, amplification, and purification, and 13 were sequenced.

Conclusions: Clinicians appropriately treat C. albicans infections based on apparent pathogenicity with antifungal medications, however while colonizing isolates are treated less frequently, the proportion treated remains substantial. Propensity for infection may be predicted by specimen type, neutrophil count, and prior history. Data on genotypic variations are pending. Genotypic variations may eventually serve as indicators of infection and proper antifungal treatment.