Microbiological Characterization of Wickerhamomyces anomalus in Clinical Isolates Obtanied from Patients with Fungemia Assisted in Brazilian Medical Centers

• Grant number: 25/05265-0
• Support Opportunities: Scholarships in Brazil - Master
• Start date: June 01, 2025
• End date: January 31, 2027
• Field of knowledge: Health Sciences - Medicine
• Principal Investigator: Arnaldo Lopes Colombo
• Grantee: Larissa Caldas Farias Yamaguchi
• Host Institution: Escola Paulista de Medicina (EPM). Universidade Federal de São Paulo (UNIFESP). Campus São Paulo. São Paulo , SP, Brazil
• Associated research grant: 21/10599-3 - The Antimicrobial Resistance Institute of São Paulo (The Aries Project), AP.CEPID

Abstract

Wickerhamomyces anomalus (syn. Hansenula anomala, Pichia anomala,Candida pelliculosa) is a yeast widely distributed in the environment, beingoften isolated from various sources such as soil, wheat and soybean grains, juicesfruits, insects and humans. In addition to its important role in the food industry,especially in the production and improvement of wine quality, W. anomalusis also recognized for its ability to produce toxins with potent activityantifungal in vitro, demonstrating efficacy against a variety of pathogensfungi, including Penicillium and Aspergillus species, Candida albicans,Saccharomyces cerevisiae, among others [1-4].Although traditionally considered a rare pathogen in humans, studiescarried out in recent decades have demonstrated an increase in the incidence of episodesof fungemia caused by W. anomalus, with high mortality rates, which canreach up to 38.5% [5,6]. Hospital outbreaks of W. anomalus have been documented in countries in Asia andfrom South America [5,7]. In this context, a recent literature review, which included36 publications and covered 170 patients with fungemia caused by this species, revealed that78.5% of infections were acquired in hospital settings (102 of 130 patients)[5]. In Brazil, our group documented an outbreak of W. anomalus in apediatric intensive care, which affected 17 children between October 2002 and January2004. The clinical isolates were characterized through sequencing of theITS region of rDNA, suggesting high genetic similarity between the sequencesanalyzed, which is compatible with hospital transmission of these infections [8]. NodeHowever, the potential source of spread has not been determined, as the yeastwas not found in the hands of healthcare professionals, hospital supplies or in thepediatric treatment unit. Regarding the sensitivity profile to antifungals,W. anomalus presents higher minimum inhibitory concentration (MIC) values,when compared to Candida albicans, against 5-flucytosine, itraconazole,voriconazole and fluconazole [5,6]. On the other hand, the species is generally sensitive toamphotericin B and echinocandins [5].Despite the relevance of invasive infections by W. anomalus, itsCurrent knowledge is predominantly based on case reports published inliterature. Consequently, our understanding of its characteristicsmicrobiological, epidemiological and clinical data is still limited. In this context, thecharacterization of W. anomalus isolates obtained from documented cases of fungemiain different medical centers in Brazil can deepen our understanding of thepopulation dynamics of this species as well as its sensitivity profile toregion.