P208 Genetic diversity of the emerging human fungal pathogen Pichia norvegensis

POSTER SESSION 2, SEPTEMBER 22, 2022, 12:30 PM - 1:30 PM: OBJECTIVES: Pichia norvegensis (= Candida norvegensis) is increasingly isolated from hospital settings, especially from immunocompromised patients. Understanding this rare pathogen, including its emergence and distribution, is crucial for accurate diagnosis and infection prevention. We studied the genetic diversity of a large collection of clinical P. norvegensis isolates obtained from Dutch hospitals along with a set of non-Dutch clinical and environmental isolates. METHODS: Clinical (n = 236; 90.8%) and environmental (n = 24; 9.2%) P. norvegensis isolates were subjected to Amplified Fragment Length Polymorphism (AFLP) fingerprinting and a novel six-loci microsatellite typing panel. Data were analyzed with BioNumerics and Structure. We applied a novel mating-type assay to determine the MATα locus presence/absence. RESULTS: AFLP fingerprinting separated the P. norvegensis isolates into three main clusters. Two clusters fully consist of clinical isolates, the third represented a mix of clinical and environmental isolates. By microsatellite typing, the overall genetic diversity was low (Simpson's D = 0.90), due to a large number of Dutch clinical isolates with similar genotypes. Minimum spanning tree analysis showed that Dutch clinical isolates fell into two clusters. Environmental and non-Dutch isolates were more distantly related. Structure analysis showed the presence of four genotypes, with signs of genetic admixture between geographic locations and environmental/clinical isolates. Nearly all isolates harbor the MATα mating-type allele. CONCLUSIONS: The P. norvegensis isolates obtained from Dutch hospitals appeared to be largely clonal, independent of geographic origin and isolation date. The observed clonality is supported by the extensive number of MATα isolates. Microsatellite typing indicated potential admixture between clinical and environmental isolates.