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New and emerging yeast pathogens
1Department of Pathology, University of Virginia Health Sciences Center, Charlottesville 22908, USA.
Abstract:
The most common yeast species that act as agents of human disease are Candida albicans, Candida tropicalis, Candida glabrata, Candida parapsilosis, and Cryptococcus neoformans. The incidence of infections by other yeasts has increased during the past decade. The most evident emerging pathogens are Malassezia furfur, Trichosporon beigelii, Rhodotorula species, Hansenula anomala, Candida lusitaniae, and Candida krusei. Organisms once considered environmental contaminants or only industrially important, such as Candida utilis and Candida lipolytica, have now been implicated as agents of fungemia, onychomycosis, and systemic disease. The unusual yeasts primarily infect immunocompromised patients, newborns, and the elderly. The role of central venous catheter removal and antifungal therapy in patient management is controversial. The antibiograms of the unusual yeasts range from resistant to the most recent azoles and amphotericin B to highly susceptible to all antifungal agents. Current routine methods for yeast identification may be insufficient to identify the unusual yeasts within 2 days after isolation. The recognition of unusual yeasts as agents of sometimes life-threatening infection and their unpredictable antifungal susceptibilities increase the burden on the clinical mycology laboratory to pursue complete species identification and MIC determinations. Given the current and evolving medical practices for management of seriously ill patients, further evaluations of the clinically important data about these yeasts are needed.
Insights
Emerging yeast pathogens, including previously overlooked species, are causing serious human infections, particularly in vulnerable populations. Clinical mycology labs face challenges in identifying these unusual yeasts and determining their unpredictable antifungal resistance.
Area of Science:
- Medical Mycology
- Infectious Diseases
- Clinical Microbiology
Background:
- Common yeasts like Candida albicans and Cryptococcus neoformans cause most human infections.
- An increasing incidence of infections caused by less common or emerging yeast species has been observed.
- Organisms previously considered non-pathogenic or industrially relevant are now implicated in human diseases.
Purpose of the Study:
- To highlight the growing threat of unusual yeast pathogens in human disease.
- To discuss the challenges in identifying these yeasts and their antifungal susceptibility.
- To emphasize the need for improved diagnostic and management strategies for yeast infections.
Main Methods:
- Review of current literature on yeast infections and emerging pathogens.
- Analysis of clinical implications of infections caused by unusual yeasts.
- Discussion of diagnostic limitations and antifungal resistance patterns.
Main Results:
- Emerging yeast pathogens include Malassezia furfur, Trichosporon beigelii, and various Candida species (e.g., Candida lusitaniae, Candida krusei).
- Unusual yeasts often infect immunocompromised individuals, neonates, and the elderly.
- Antifungal susceptibility of these yeasts varies widely, with some showing resistance to standard treatments like azoles and amphotericin B.
Conclusions:
- Unusual yeasts pose a significant and growing challenge in clinical settings.
- Current identification methods may not be sufficient for rapid diagnosis of these emerging pathogens.
- Accurate identification and antifungal susceptibility testing are crucial for effective patient management and combating life-threatening infections.