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In vitro susceptibility testing and DNA typing of Saccharomyces cerevisiae clinical isolates
L Zerva1, R J Hollis, M A Pfaller
1Department of Pathology, University of Iowa College of Medicine, Iowa City 52242, USA.
Abstract:
Saccharomyces spp. are widely distributed in nature and may colonize the normal human gastrointestinal tract. Although Saccharomyces cerevisiae isolates have been previously considered nonpathogenic, they appear to be increasingly associated with infections in immunocompromised or otherwise debilitated patients. The antifungal susceptibility and epidemiology of S. cerevisiae are poorly defined at present. A series of 76 isolates (mostly stool surveillance and throat swab isolates) from 70 bone marrow transplant patients hospitalized at two different medical centers were characterized by antifungal susceptibility testing and restriction endonuclease analysis of chromosomal DNA. For DNA typing, digestion with NotI followed by pulsed-field gel electrophoresis was applied. Typing results revealed 62 distinct DNA types among the 76 clinical isolates. Despite this genomic diversity, clusters of identical isolates were identified among different patients hospitalized concurrently in the same unit, indicating possible nosocomial transmission. The MICs of amphotericin B, 5-fluorocytosine, fluconazole, and itraconazole were determined by a broth microdilution method, as recommended by the National Committee for Clinical Laboratory Standards. The MICs at which 90% of the strains were inhibited were as follows: amphotericin B, 1.0 micrograms/ml; 5-fluorocytosine, 0.25 micrograms/ml; fluconazole, 8.0 micrograms/ml; and itraconazole, 1.0 micrograms/ml. The relative resistance of S. cerevisiae to fluconazole and itraconazole may promote the emergence of this species as a pathogen among immunosuppressed patients.
Insights
Saccharomyces cerevisiae, a yeast, is increasingly causing infections in vulnerable patients. This study analyzed its genetic diversity and antifungal resistance, revealing potential hospital-acquired infections and highlighting resistance to fluconazole and itraconazole.
Area of Science:
- Medical Mycology
- Clinical Microbiology
- Infectious Diseases
Background:
- Saccharomyces cerevisiae, a yeast, is commonly found in the human gut but is increasingly linked to infections in immunocompromised individuals.
- The antifungal susceptibility and epidemiology of Saccharomyces cerevisiae infections remain poorly understood.
- Bone marrow transplant patients are particularly susceptible to opportunistic infections.
Purpose of the Study:
- To characterize the genetic diversity of Saccharomyces cerevisiae clinical isolates.
- To determine the antifungal susceptibility profiles of these isolates.
- To investigate the potential for nosocomial transmission of Saccharomyces cerevisiae.
Main Methods:
- Collected 76 Saccharomyces cerevisiae isolates from 70 bone marrow transplant patients across two medical centers.
- Performed DNA typing using NotI digestion and pulsed-field gel electrophoresis.
- Determined antifungal susceptibility using broth microdilution for amphotericin B, 5-fluorocytosine, fluconazole, and itraconazole.
Main Results:
- Identified 62 distinct DNA types among the 76 clinical isolates, indicating significant genomic diversity.
- Detected clusters of identical isolates in patients hospitalized concurrently, suggesting possible nosocomial transmission.
- Established MIC90 values: amphotericin B (1.0 µg/ml), 5-fluorocytosine (0.25 µg/ml), fluconazole (8.0 µg/ml), and itraconazole (1.0 µg/ml).
Conclusions:
- Saccharomyces cerevisiae exhibits considerable genomic diversity, but hospital-acquired transmission is evident.
- The observed resistance of Saccharomyces cerevisiae to fluconazole and itraconazole may contribute to its emergence as a significant pathogen in immunosuppressed populations.
- Further research is needed to understand the clinical implications and management of Saccharomyces cerevisiae infections.