Abstract
Candida dubliniensis shares a wide range of phenotypic characteristics with Candida albicans including a common trait called germ tube positivity. Hence, laboratory differentiation of these two species is cumbersome. Duplex PCR analyses for C. albicans and C. dubliniensis was performed directly on DNA extracted from a total of 122 germ tube positive isolates derived from 100 concentrated oral rinse samples from a random cohort of diabetics attending a clinic in Sri Lanka. These results were confirmed by DNA sequencing of internal transcribed spacer (ITS) region of rDNA of the yeasts. Performance efficacy of duplex PCR was then compared with phenotypic identification using a standard battery of phenotypic tests. Of the 122 germ tube positive isolates three were identified by duplex PCR as C. dubliniensis and the remainder as C. albicans. On the contrary, when the standard phenotypic tests, sugar assimilation and chlamydospore formation, were used to differentiate the two species 13 germ tube positive isolates were erroneously identified as C. dubliniensis. Duplex PCR was found to be rapid, sensitive and more specific than phenotypic identification methods in discriminating C. dubliniensis from C. albicans. This is also the first report on the oral carriage of C. dubliniensis in a Sri Lankan population.
Highlights
Candida dubliniensis is an emerging medically relevant pathogenic yeast (Sullivan et al 1995) associated with oral, vaginal, and systemic infections in patients with human immunodeficiency virus infection and diabetes mellitus (Krcmery and Barnes 2002; Sullivan et al 1995)
Extracted deoxyribonucleic acid (DNA) from oral rinse specimens and germ tube positive isolates were subjected to duplex polymerase chain reaction (PCR) to differentiate C. albicans from C. dubliniensis
Duplex PCR of the concentrated oral rinse samples When the extracted DNA from pellets of 100 concentrated rinse samples were directly subjected to duplex PCR three samples were positive for C. dubliniensis and the remainder were positive for C. albicans only
Summary
Candida dubliniensis is an emerging medically relevant pathogenic yeast (Sullivan et al 1995) associated with oral, vaginal, and systemic infections in patients with human immunodeficiency virus infection and diabetes mellitus (Krcmery and Barnes 2002; Sullivan et al 1995). Several phenotypic and genotypic tests have been developed, validated and applied to differentiate C. albicans from C. dubliniensis. Polymerase chain reaction PCR (Ellepola et al 2003) and duplex PCR (Ahmad et al 2012) have been recently used as genotypic tests for rapid identification and differentiation of the two species. We report a comparison of well described phenotypic methods with the duplex PCR assay (Ahmad et al 2012) using primers derived from unique ribosomal deoxyribonucleic acid (rDNA) sequences for rapid detection and differentiation of C. albicans and C. dubliniensis. The was assays were performed using yeast isolates derived from oral rinse samples from a cohort of diabetic patients attending a clinical facility in Colombo, Sri Lanka
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