Candida auris is an emerging fungal pathogen associated with outbreaks in healthcare settings. We report a multiyear outbreak of C. auris in a burn intensive care unit in Illinois, USA, during 2021-2023. We identified 28 C. auris cases in the unit over a 2-year period, despite outbreak response and multimodal mitigation measures. Of the 28 case-patients, 15 (53.6%) were considered colonized and 13 (46.4%) had clinical infections. Phylogenetic analysis of whole-genome sequences revealed 4 distinct clusters of closely related (0-6 SNP differences) genomes containing 3-6 cases. Clusters generally contained temporally related isolates from patients with epidemiologic links; this finding suggests that multiple introductions and within-unit spread over a limited time were responsible for the outbreak, rather than transmission from a long-term source (e.g., persistent environmental contamination or staff carriage). Here, integrated traditional and genomic epidemiology supported C. auris outbreak investigation and response and informed targeted interventions.
Candida auris is a fungal pathogen associated with colonization and high-mortality invasive infections in persons with underlying medical conditions, especially those who are hospitalized or reside in long-term care facilities (1,2). Prolonged skin colonization and environmental contamination likely contribute to within-facility persistence and spread (2-5). C. auris often displays extensive antifungal resistance and can acquire resistance rapidly during antifungal treatment (6-8).
Intensive care units (ICUs) are particularly vulnerable to C. auris outbreaks because of prolonged patient stays, high medical acuity, and extensive use of medical devices that can encourage pathogen spread (9-12). Effective infection prevention strategies are key to curbing the spread of C. auris; those strategies include contact screening, strict hand hygiene procedures, appropriate use of personal protective equipment (PPE) and transmission-based precaution by healthcare providers, use of single-patient equipment, environmental cleaning and disinfection, and private-room isolation (13). However, C. auris colonization and transmission have been reported to persist despite aggressive infection prevention interventions, making C. auris control a long-term burden in affected facilities (12,14,15).
In burn ICUs (BICUs), patients are at increased risk for healthcare-acquired infections because of breakdown of the skin barrier and the immunocompromising effects of burns; infection is the leading cause of death after burn injury (16). Fungal wound infections are reported in 6%-45% of all burn admissions; candidemia develops in up to 5% of patients with severe burns. Unlike most Candida species, C. auris has a tropism for skin (17), and it can readily colonize or infect adjacent large open, nutrient-rich burn wounds. Furthermore, because they have frequent infections and large, open wounds, burn patients often require treatment with systemic and topical antimicrobials, both of which have capacity to eliminate competitive microbiota and encourage colonization with resistant organisms such as C. auris. Care provided in BICUs, such as skin debridement, may disperse colonized or infected skin cells into the environment, which contributes to transmission.
We describe a C. auris outbreak and response in a BICU in Illinois beginning in 2021. We used whole-genome sequencing (WGS) to help refine epidemiologic inferences and direct interventions. WGS has been used to support epidemiologic investigations of C. auris infection, including hospital outbreaks (9,18-23). Outbreak sequences generally form a unique clade with limited diversity (9,18); close relationships have been observed between epidemiologically linked cases (median 7 SNPs) and isolates from the same person (median 2 SNPs) (21). WGS can also detect antifungal resistance mutations (19,24,25). Thus, WGS may be a powerful tool to support C. auris outbreak investigations.