Journal of Clinical Microbiology, December 1999, p. 3804-3808, Vol. 37, No. 12
0095-1137/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
-Methyl-D-Glucoside as Determined with the API 20C
AUX and Vitek YBC Systems
Departments of Pathology1 and Biology,3 University of Iowa, Iowa City, Iowa; Department of Oral Medicine and Pathology, School of Dental Science, and Dublin Dental Hospital, Trinity College, University of Dublin, Dublin 2, Republic of Ireland4; and Department of Medicine, Division of Infectious Diseases, Universidade Federal de Sao Paulo, Sao Paulo, Brazil2
Received 3 May 1999/Returned for modification 28 June 1999/Accepted 20 August 1999
To have a better understanding of the role of Candida
dubliniensis in clinical infections, it is essential that
microbiology laboratories can identify this species rapidly and
accurately in clinical specimens. C. dubliniensis has been
reported to lack the ability to utilize xylose (XYL) and
-methyl-D-glucoside (MDG) and to grow poorly or not at
all at 45°C, whereas Candida albicans isolates utilize
XYL and MDG and usually grow well at 45°C. We tested 66 isolates of
C. dubliniensis and 100 isolates of C. albicans with both the API 20C AUX and Vitek YBC systems to evaluate the ability
of the XYL and MDG tests contained within each of these systems to
distinguish between the two species. The ability to grow at 45°C was
also examined. None of the C. dubliniensis isolates grew at
45°C, and 23 of 100 C. albicans isolates (23%) exhibited poor or no growth at 45°C. The XYL and MDG tests contained within the
API 20C AUX system were both negative for all 66 C. dubliniensis isolates and were positive for 98 (XYL) and 56 (MDG)
of the 100 C. albicans isolates. With the Vitek system, 64 of 66 C. dubliniensis isolates (97.0%) were XYL negative
and 63 (95.0%) were MDG negative. Conversely, 96 of 100 C. albicans isolates (96.0%) were XYL positive and 100 (100.0%)
were MDG positive with the Vitek system. Clinical microbiology
laboratories could use lack of growth at 45°C and a negative XYL test
with either the API 20C AUX or Vitek yeast identification system to
provide a presumptive identification of C. dubliniensis. A
negative MDG test result with either system would also be helpful but
may misclassify C. albicans as C. dubliniensis, especially when the API 20C AUX system is used.
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