Indixanol contrast medium partially separates infectious strains of Candida into persister and non-persister populations

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Dr. Bryan Larsen Ph.D

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Medicine and Health Sciences


Candida albicans and Candida glabrata, are two clinically relevant strains of yeast. They make up a majority of commonly seen pathologies such as vaginal yeast infections, nosocomial infections, and infections of immunocompromised patients. Candida stains can form perisiter colonies, which have reduced metabolic activity and increased resistance to antifungal treatment. Observing survival after a heat challenge provides a method for demonstrating the persister state among yeast and allows investigation of environmental conditions that increase or decrease the persistership of a microbial culture. Persisters are also resistant to antifungals like Amphotericin. It has been demonstrated that Saccharomyces could be separated into perisiter and non-persister populations by centrifuging a culture atop a 30% indixanol density cushion. The applicability of this technique to the more clinically relevant Candida albicans became the principal aim of this study. The indixanol separation, following assiduously the reported protocol, was applied to two strains of C. albicans as well as one C. glabrata. The protocol for Saccharomyces used 7 day-old cultures to enhance the number of persisters. In our hands, most of the organisms were found in the pellet, which was purported to be the persister portion of the population. Flow cytometry was used to quantify the percent of the culture found in the upper versus the pellet layer. Viability demonstrated by growth on agar plates following heat treatment revealed that vegetative cells were found in both layers, but most vegetative cells remained in the upper layer. Amphoteri-cin B treatment for 30 minutes followed by heat treatment reduced the number of per-sisters. A shorter growth time (2 days increased the number of vegetative cells and substantially reduced the size of the pellet. Conclusion: This method provides an incomplete separation of persisters and vegetative cells but may have utility in screening compounds for anti-persister activity.


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