Downloaded from www.microbiologyresearch.org by IP: 54.70.40.11 On: Fri, 12 Oct 2018 01:07:26 Identification and characterization of nine atypical Candida dubliniensis clinical isolates Olatz Albaina, 1 Ismail H. Sahand, 1,2 Marı ´a I. Brusca, 3 Derek J. Sullivan, 4 In ˜ igo Ferna ´ ndez de Larrinoa 5 and Marı ´a D. Moragues 1,6 Correspondence Marı ´a D. Moragues lola.moragues@ehu.es Received 26 May 2014 Accepted 27 November 2014 1 Departamento de Inmunologı ´a, Microbiologı ´a y Parasitologı ´a, Facultad de Medicina y Odontologı ´a, University of the Basque Country UPV/EHU, Bilbao, Spain 2 Department of Microbiology, Faculty of Medicine, Hawler Medical University, Hawler, Kurdistan, Iraq 3 Departamento de Microbiologı ´a y Parasitologı ´a, Facultad de Odontologı ´a, Universidad de Buenos Aires, Argentina 4 Microbiology Research Laboratory, Division of Oral Biosciences, School of Dental Science and Dublin Dental University Hospital, Trinity College, Dublin 2, Ireland 5 Departamento de Quı ´mica Aplicada, Facultad de Ciencias Quı ´micas, University of the Basque Country UPV/EHU, Donostia-San Sebastia ´ n, Spain 6 Departamento de Enfermerı ´a I, Escuela Universitaria de Enfermerı ´a, University of the Basque Country UPV/EHU, Bilbao, Spain Candida dubliniensis is a pathogenic yeast of the genus Candida closely related to Candida albicans. The phenotypic similarity of these two species often leads to misidentification of C. dubliniensis isolates in clinical samples. DNA-based methods continue to be the most effective means of discriminating accurately between the two species. Here, we report on the identification of nine unusual Candida isolates that showed ambiguous identification patterns on the basis of their phenotypic and immunological traits. The isolates were categorized into two groups. Group I isolates were unable to produce germ tubes and chlamydospores, and to agglutinate commercial latex particles coated with a mAb highly specific for C. dubliniensis. Group II isolates grew as pink and white colonies on CHROMagar Candida and ChromID Candida, respectively. Carbohydrate assimilation profiles obtained with API/ID32C together with PCR amplification with specific primers and DNA sequencing allowed reliable identification of the nine unusual clinical isolates as C. dubliniensis. INTRODUCTION The incidence of systemic and mucosal infections caused by species of the genus Candida has increased dramatically in recent decades. Candida albicans is considered the most pathogenic species of the genus Candida, and the most common cause of deep and superficial candidiasis (Coleman et al., 1997b). In addition to the elevated prevalence of infections caused by C. albicans, other species such as Candida glabrata, Candida tropicalis, Candida dubliniensis, Candida parapsilosis, Candida krusei and Candida guillier- mondii are also associated with invasive candidiasis in humans (Krcmery & Barnes, 2002). C. dubliniensis is an opportunistic yeast of the genus Candida associated primarily with oral candidiasis (Sullivan & Coleman, 1998; Sullivan et al., 1995) in human patients infected with human immunodeficiency virus (HIV) or with AIDS (Gugnani et al., 2003; Patel et al., 2012; Sullivan et al., 2004). In addition, this species has been described to a lesser extent in healthy individuals and people not infected with HIV, but affected by severe underlying illnesses such as diabetes, cystic fibrosis or cancer (Coleman et al., 1997b; Dahiya et al., 2003; Davies et al., 2002; Lai et al., 2013; Manfredi et al., 2002; Parmeland et al., 2013; Peltroche-Llacsahuanga et al., 2002; Willis et al., 2000; Yu et al., 2012). Genome sequence analysis has confirmed the very close relationship between C. dubliniensis and C. albicans (Jackson et al., 2009); unsurprisingly, the two species share many phenotypic traits which complicate the identification of C. dubliniensis clinical isolates by conventional mycological Abbreviations: IFA, immunofluorescence assay; ITS, internal transcribed spacer. The GenBank/EMBL/DDBJ accession numbers for the large subunit rRNA gene sequences corresponding to the group I isolates are KF537273, KF537274 and KF537275. Journal of Medical Microbiology (2015), 64, 147–156 DOI 10.1099/jmm.0.078832-0 078832 G 2015 The Authors Printed in Great Britain 147