Abstract

Candida albicans is both a human commensal and opportunistic pathogen. Nosocomial infections due to pathogenic C. albicans are the fourth l argest i n North America and carry significant socioeconomic burden. Systemic Candida i nfections of i mmune-compromised individuals are frequently l ethal even when treated optimally. Drug resistance i s sometimes due to the pre-existence of genetic polymorphisms that bypass the mode of action of the drug. In other cases, resistance i s acquired via the evolution of genetic polymorphisms. There is evidence that C. albicans possesses a drug tolerance response which “buys time” for individuals to gain such beneficial mutations. Our goal i s to characterize this poorly understood epigenetic cytoprotective program at the single cell molecular level. Our hypothesis i s that i ndividuals will respond differently to drug exposure. Some will not mount a sufficient epigenetic response and die, while others will survive using different pathways. We modified a single cell platform for the fungal setting and used it to transcriptionally profile thousands of treated and untreated cells at early (tolerance) and late (resistance) timepoints. Untreated populations exhibit multivariate epigenetic responses with individuals partitioning into distinct subpopulations, each with a unique survival strategy involving efflux pumps, chaperones, transport mechanisms, and cell wall maintenance. Cell imaging will be used to validate these observations. Whole genome DNA-sequencing will be used to determine i f there i s i ncreased i nstability during the tolerance phase. Targeting the tolerance response concomitantly with standard therapies could represent an efficient approach to ablating clinical persistence.