Prevalence Rates, Species Distribution and Antifungal Susceptibility of Rare Candida and Related Saccharomycotina Yeasts Causing Bloodstream Infections in 28 Medical Centres

Abstract

Background: There is a lack of contemporary studies addressing the prevalence rates and antifungal susceptibility of bloodstream infections (BSI) caused by rare yeasts (RY) from the Saccharomycotina subphylum.

Objectives: This 16-year multicentre study (2007-2023) aimed to assess the prevalence and antifungal susceptibility of rare yeasts isolated from BSIs in 28 Brazilian tertiary care hospitals.

Methods: Yeasts from the Saccharomycotina subphylum, excluding common Candida species and Basidiomycota, were selected from BSI episodes. Species were identified using proteomics and molecular methods. Antifungal susceptibility testing was performed by EUCAST broth microdilution.

Results: Among 2655 BSI episodes, 100 (3.76%) involved rare yeasts. Prevalence showed a slight, non-significant increase from 3.16% (2007-2015) to 4.17% (2016-2023; p = 0.183). A total of 11 genera and 20 species were identified, with Clavispora lusitaniae (20%), Wickerhamomyces anomalus (16%), Candida haemulonii (14%) and Candida duobushaemulonii (12%) being the most frequent species. Eight species, including Pichia kluyveri and Kodamaea ohmeri, appeared only in the latter period. Most rare yeasts showed low MICs to amphotericin B and anidulafungin, except for Clavispora lusitaniae, Candida haemulonii and Candida duobushaemulonii, which were less susceptible to amphotericin B. Wickerhamomyces anomalus and Candida duobushaemulonii also showed reduced susceptibility to fluconazole.

Conclusions: This study provides valuable insights into the prevalence rates, species distribution and antifungal susceptibility of rare yeasts causing BSIs in tertiary care hospitals. Our findings highlight the need for continuous surveillance, incorporation of new diagnostic and tailored therapeutic strategies to mitigate morbidity and mortality due to invasive infections caused by emerging fungal pathogens.

Keywords: Candida; Candidemia; Fungemia; Saccharomycotina yeasts; antifungal resistance; emerging yeast pathogens; invasive fungal infections; rare yeast infections.