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Indian Journal of Medical Microbiology
Medknow Publications on behalf of Indian Association of Medical Microbiology
ISSN: 0255-0857 EISSN: 1998-3646
Vol. 25, Num. 3, 2007, pp. 304-305

Indian Journal of Medical Microbiology, Vol. 25, No. 3, July-September, 2007, pp. 304-305

Correspondence

A novel method for differentiation of Candida dubliniensis from other Candida species

Wabale VR, Kagal AS, Mani RS, Bharadwaj R

Department of Microbiology, Grant Medical College, Mumbai - 400 008, Maharashatra
Correspondence Address: Department of Microbiology, Grant Medical College, Mumbai - 400 008, Maharashatra
rwabale@gmail.com

Date of Submission: 27-Dec-2006
Date of Acceptance: 25-Mar-2007

Code Number: mb07088

Dear Editor,

Candida dubliniensis is being increasingly reported as an opportunistic infection in patients with human immunodeficiency virus (HIV) infection. [1] It has an ability to rapidly develop fluconazole resistance in vitro ; therefore, it is important to identify it. [2] C. dubliniensis and C. albicans have a close genotypic relationship resulting in sharing a broad range of phenotypic characteristics. This hampers the accurate and rapid differentiation of the two species. We utilized Staib agar media for differentiating the isolates of C. dubliniensis from other Candida spp .

The present study comprised 63 clinical isolates of C. albicans, C. dubliniensis, C. parapsilosis, and C. tropicalis including two reference strains of C. albicans (CA132A) and C. dubliniensis (CD36). As described by Staib et al ., [2] colonial morphology of C. dubliniensis is observed on Staib agar along with the characteristics of chlamydospores produced by these Candida spp. C. dubliniensis and C. parapsilosis showed rough colonies with fine fringe on this media. However, C. parapsilosis could be easily differentiated as no chlamydospores were produced by this species, while C. dubliniensis produced chlamydospores in characteristic doublets and triplets. C. albicans and C. tropicalis produced mucoid colonies without fine edges and no chlamydospore production on this media [Figure - 1].

The currently used important tests to differentiate C. dubliniensis from C. albicans are colony color on CHROM agar Candida medium, lack of growth at 45°C, PCR, [3] immunofluorescence, [4] and co-aggregation with Fusobacterium nucleatum tests. [5]

Staib et al. reported that growth on Staib agar was an efficient means of differentiating C. dubliniensis and C. albicans . However, Mosaid et al . [6] reported that colony morphology rather than chlamydospore production was more accurate for species identification. Our results suggest that colony morphology along with chlamydospore production on Staib agar when used in combination easily differentiates C. dubliniensis from other Candida isolates in clinical samples. The proposed method of phenotypic differentiation on Staib agar has a number of advantages over carbohydrate profile analysis as well as over commercially available yeast identification systems. It is rapid, reliable, easy to perform, inexpensive, readily available, and amenable to the analysis of large number of isolates. Thus, Staib agar provides a simple test for accurate identification of C. dubliniensis from clinical samples .

Acknowledgement

We would like to thank Sullivan DJ and Coleman DC for providing us with the reference strains of C. albicans and C. dubliniensis.

References

1.Moran GP, Sullivan DJ, Henman MC, McCreary CE, Harrington BJ, Shanley DB, et al . Antifungal drug susceptibilities of oral Candida dubliniensis isolates from human immunodeficiency virus (HIV)-infected and non-HIV-infected subjects and generation of stable fluconazole-resistant derivatives in vitro. Antimicrob Agents Chemother 1997; 41 :617-23.  Back to cited text no. 1  [PUBMED]  [FULLTEXT]
2.Staib P, Morschhauser J. Chlamydospore formation on Staib agar as a species-specific characteristic of Candida dubliniensis. Mycoses 1999; 42 :521-4.  Back to cited text no. 2    
3.Sullivan DJ, Moran G, Donnelly S, Gee S, Pinjon E. Candida dubliniensis : An update. Rev Iberoam Micol 1999; 16 :72-6.   Back to cited text no. 3    
4.Bikandi J, Millan RS, Moragues MD, Cebas G, Clarke M, Coleman DC, et al. Rapid identification of Candida dubliniensis by indirect immunofluorescence based on differential localization of the antigens on Candida dubliniensis blastospores and Candida albicans germ tubes. J Clin Microbiol 1998; 36 :2428-33.  Back to cited text no. 4    
5.Jabra-Rizk MA, Falkler WA Jr, Merz WG, Kelley JI, Baqui AA, Meiller TF. Coaggregation of Candida dubliniensis with Fusobacterium nucleatum. J Clin Microbiol 1999; 37 :1464-8.  Back to cited text no. 5  [PUBMED]  [FULLTEXT]
6.Al Mosaid A, Sullivan D, Salkin IF, Shanley D, Coleman DC. Differentiation of Candida dubliniensis from Candida albicans on Staib agar and Caffeic acid-ferric citrate agar. J Clin Microbiol 2001; 39 :323-7.  Back to cited text no. 6  [PUBMED]  [FULLTEXT]

Copyright 2007 - Indian Journal of Medical Microbiology

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