Development of differential media for Candida dubliniensis and identification of a novel clade of Candida dubliniensis predominant in the Middle East

Abstract

Candida dubliniensis is a newly described Candida species originally associated with oral colonisation and candidosis in Human Immunodeficiency Virus (HlV)-infected, and acquired immunodeficiency syndrome (AIDS) patients. More recently, C. dubliniensis has been isolated from cases of infection in other groups of immunocompromised individuals and in patients with severe underlying diseases. However, the close genotypic relationship between C. dubliniensis and C. albicans results in their sharing a broad range of phenotypic characteristics which hampers the accurate and rapid differentiation of the two species. Therefore, the phenotypic methods currently available for the identification of C. dubliniensis all have disadvantages in that they are time consuming, expensive or in some cases, unreliable. The first part of the present study investigated the usefulness of a variety of culture media including; Staib, caffeic acid-ferric citrate (CAF), Pal’s, tobacco and casein agar media to effectively differentiate between isolates of C. dubliniensis and C. albicans based on colony morphology and/or chlamydospore production. The results showed that all C. albicans tested, apart from nine isolates (7.5%) grown on casein agar, did not produce chlamydospores when cultured on the different media. In contrast, 111/ 130 (85.4%) 109/130 (83.8%) 52/53 (98%) and 106/ 109 (97.2%) of the C. dubliniensis isolates tested produced chlamydospores on Staib, CAF, tobacco and casein agars, respectively.