Candida albicans is the predominant pathogenic
Candida species in susceptible human host. Infections caused by non-
albicans Candida spp. have, however, also increased in recent years and may account for up to 60% of all episodes of candidemia or invasive candidiasis at some centers [
1,
2].
Candida dubliniensis, first described in 1995 from oral cavities of human immunodeficiency virus-infected individuals [
3], is increasingly being reported from patients with candidemia in recent years [
1,
2,
4].
C. dubliniensis shares several phenotypic characteristics, such as ability to form chlamydospores on cornmeal agar and germ tubes in serum with
C. albicans. Since germ tube test is routinely used for the differentiation of
C. albicans from other
Candida species, identification based solely on this test leads to misidentification of some
C. albicans isolates in routine diagnostic laboratories [
5]. Accurate identification is warranted since
C. dubliniensis exhibits increased adherence to buccal epithelial cells and is more likely to develop resistance against fluconazole and other azoles [
6,
7].
Several phenotypic tests based on colony morphology and physiological assimilation tests have been developed to distinguish
C. albicans from
C. dubliniensis. Commercially available yeast identification systems (Vitek 2 ID-YST, API 20C and ID32C) based on utilization of various compounds have been used for differentiating various
Candida spp., however, these methods are expensive and require at least 1–2 days to report results [
8]. Formation of rough/fringed colonies by germ tube positive isolates on differential media such as Niger seed agar [
9], simplified sunflower seed agar (SSA) [
10], or tobacco agar [
11], or inability to grow in a hypertonic Sabouraud dextrose broth containing 6.5 M NaCl [
12] are often used to differentiate
C. albicans from
C. dubliniensis. A commercial latex agglutination test (Bichro-Dubli Fumouze) is also available [
13]. However, prior presumptive identification of
C. albicans/C. dubliniensis is required before phenotypic methods could be used for their differentiation. Also, variations in growth conditions (incubation temperature, repeated subculturing and storage) may impede accurate identification of these two species by phenotypic tests. Unambiguous identification can be established only by molecular techniques and PCR-based methods are mostly employed [
5]. Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) has also been exploited recently for identification and differentiation of cultured yeast isolates including even closely related
Candida spp. [
14]. However, the high cost of the equipment is a major impediment for its widespread use in resource-limited settings. In this study, we have developed a novel duplex PCR assay by using primers derived from unique rDNA sequences for rapid detection and differentiation of
C. albicans and
C. dubliniensis. The performance of duplex PCR was compared with three phenotypic methods for identification of clinical isolates as
C. albicans or
C. dubliniensis.