Pseudo-Outbreak of <i>Purpureocillium lilacinum</i> Skin Infections at a Dermatology Clinic — Washington, 2024

In April 2024, a Washington dermatology clinic reported multiple cases of atypical fungal skin infections caused by the environmental mold Purpureocillium lilacinum to Clallam County Public Health. P. lilacinum most frequently causes skin infections among immunocompromised persons but can occasionally infect immunocompetent persons. The diagnoses were made on the basis of swab specimens collected from patients' skin to diagnose a fungal skin infection, rather than from a biopsy or skin scraping, as is recommended. An investigation by the Washington State Department of Health and CDC revealed this to be a pseudo-outbreak caused by contaminated saline, ultimately affecting 22 patients during January-October 2024. The investigation found that the clinic had refilled and reused saline squeeze bottles during skin swab collection. This resulted in contamination of the saline with P. lilacinum, which was transferred to the skin when swab specimens were obtained. Whole genome sequencing confirmed that P. lilacinum isolates from patient swab specimens were closely related to environmental isolates from the contaminated bottles. The clinic discontinued use of refillable squeeze bottles in January 2025 and transitioned to single-use saline packets, after which no further cases were reported. This investigation underscores the importance of proper diagnostic specimen collection procedures and infection prevention and control practices in clinical settings.