NOVEL YEAST, ORIGINALLY DETECTED IN AFRICA, NOW ISOLATED FROM WOMEN IN THE UNITED STATES
EMBARGOED UNTIL: Thursday, September 12, 11:00 AM MDT
(Session 169, Paper M-1382)
Kevin Hazen
Duke Univ. Hlth. Syst., Durham, NC, United States
Email: kevin.hazen@duke.edu
Phone: 919-684-2562
A yeast that was initially detected in Africa and subsequently in Europe and Great Britain has now been isolated from six female patients in the United States. The yeast, which has the biological name of Candida africana, differs from the yeast Candida albicans, the common agent of oral and vaginal thrush, in that it appears to be associated only with women. All isolates were obtained from genitourinary tract specimens of the female patients. The C. africana isolates were inhibited by a variety of antibiotics specific for fungi. Genetic analysis of the isolates demonstrated that C. africana is closely related to C. albicans and can easily be incorrectly identified by clinical microbiologists as C. albicans. How C. africana differs from C. albicans with regard to causing disease in the female patients will require further investigation.
The C. africana isolates were identified by the Clinical Mycology technologists at the University of Virginia (Ms. Sarah Regi) and at Duke University (Ms. Terry Byrne). The isolates were grown from clinical specimens submitted to the respective Clinical Microbiology laboratories of the universities. The studies on the isolates were overseen by Kevin C. Hazen, Ph.D. and ideas contributed by all of the authors of this presentation. The work will be presented at the Interscience Conference on Antimicrobial Agents and Chemotherapy in Denver, Colorado on September 12th, 2013.
In 2008, a urine specimen from a teenage girl was submitted for analysis by the University of Virginia Clinical Microbiology Laboratory. Typically when yeast grows from a urine specimen the identity of the yeast is Candida albicans. In this particular case, the yeast that grew did not identify by a rapid screening method as C. albicans. Additional studies suggested it was an atypical C. albicans consistent with a novel yeast originally identified in Africa during the mid-1990’s and now called Candida africana. Using DNA sequencing technology, the isolate was shown to match the isolates seen in Africa. During a five month period from 2012 to 2013, four yeast isolates were obtained from genitourinary specimens of three female patients at Duke University in North Carolina. These isolates also appeared to act like atypical C. albicans. DNA sequencing revealed that they were also similar to the isolates from Africa. Since that five month period, we have obtained additional C. africana isolates from different patients.
Studies by a research group in Great Britain suggest that C. africana is not as pathogenic as the related C. albicans and may also be less able to bind to host tissue. In the case of the female patients in our study, it is not clear whether C. africana was causing disease, but in one patient C. africana was isolated twice, suggesting it may be a potential pathogen. The fact that the isolates were obtained exclusively from the genitourinary tract of female patients supports the idea that C. africana has developed a niche specific adaptation, possibly involving response to female sex hormones.
How these patients obtained this unusual yeast is not clear. The results suggest that the organism may be prevalent in the United States but is often identified as an atypical C. albicans. If so, then recognizing that an atypical C. albicans may be C. africana would help physicians know what antifungal agents may be useful to treat a patient with C. africana infection. We tested agents representing three classes of antifungal drugs and found that the C. africana isolates were susceptible to all the agents. Thus, a patient suffering from C. africana infection has a variety of antifungal agents that could lead to successful treatment.