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Background: Diabetes mellitus is a global epidemic. Oral candidiasis is being frequently recognized in diabetic patients, due
to elevated glucose in their oral fluids and immune dysfunction.
Oral candidiasis is associated with multiple pathogens including
C.albicans, C.parapsilosis, C.glabrata and C.tropicalis. The aim of this
study was to evaluate a multiplex PCR as a rapid diagnostic tool for
identification of above four oral Candida pathogens.
Methods & Materials: A multiplex PCR was optimized to
identify C.albicans, C.parapsilosis, C.glabrata and C.tropicalis in concentrated oral rinse samples of patients with diabetes, attending
the Endocrinology clinic at Colombo South Teaching hospital, Sri
Lanka. Common reverse primer, ITS4 and four species specific forward primers targeting ITS 1 and ITS2 regions of yeast genome
(primer CA, CT, CP, and CGL respectively) were used. Oral rinse
samples (n = 100) were used to compare between multiplex PCR
and phenotypic identification.
Results: Out of the 100 oral rinse samples, 77 were culture
positive and of these 44 were colonized (> 600 CFU/ml). Multiple
Candida species including C.albicans, C.parapsilosis and C.tropicalis
were identified in 33 of the colonized samples. Eighty two patients
were positive for Candida bymultiplex PCR and of them 47 hadmultiple Candida species. All 44 colonized specimens were also positive
by multiplex PCR. C.albicans was the most predominant organism
(73/82) followed by C.parapsilosis (46/82), C.tropicalis (16/82) and
C.glabrata (6/82). In specimens with multiple species, the two most
common organisms were C.albicans and C.parapsilosis.
Out of the 61 Candida isolates that were germ tube negative,
15 isolates were identified as C.albicans by the typical green colour
on CHROMagar. However two out of fifteen isolates were negative
for C.albicans by multiplex PCR indicating that results of CHROMagar should be interpreted cautiously. Further C.glabrata could not
be identified using phenotypic identification but was identified by
multiplex PCR. Multiplex PCR yielded a sensitivity of 10 Candida
cells/ml of oral rinse sample.
Conclusion: Multiplex PCR is found to be rapid, highly sensitive
and specific than phenotypic identification methods in discriminating multiple Candida species directly in oral rinse specimens.
