Mycology Screening for amino acid substitutions in the Candida albicans Erg11 protein of azole-susceptible and azole-resistant clinical isolates: new substitutions and a review of the literature Florent Morio a,b , Cedric Loge a , Bernard Besse c , Christophe Hennequin d , Patrice Le Pape a,b, ⁎ a Université de Nantes, Nantes Atlantique Universités, Département de Parasitologie et Mycologie Médicale, EA 1155—IICiMed, Faculté de Pharmacie, 1 rue Gaston Veil, 44035 Nantes, France b CHU Nantes, Laboratoire de Parasitologie-Mycologie, Institut de Biologie, 5 allée de l'île Gloriette, 44000 Nantes, France c CHU Nantes, Laboratoire de Virologie, Institut de Biologie, 5 allée de l'île Gloriette, 44000 Nantes, France d Assistance Publique des Hôpitaux de Paris, Hôpital Saint-Antoine, Laboratoire de Parasitologie-Mycologie, 184 rue du Faubourg St Antoine, 75012 Paris, France Received 30 August 2009; accepted 12 November 2009 Abstract For several years, azole antifungal drugs have been a treatment option for potentially life-threatening Candida infections. However, azole resistance can occur through various mechanisms such as alterations in ERG11, encoding lanosterol 14α-demethylase (CYP51). In this study, we investigated the antifungal susceptibility to fluconazole, itraconazole, and voriconazole of 73 clinical isolates of Candida albicans. Screening for amino acid substitutions in Erg11 was performed on each of the 73 isolates. Twenty isolates displayed a marked decrease in azole susceptibility. Amino acid substitutions were detected in more than two-thirds of the strains. In all, 23 distinct substitutions were identified. Four have not been described previously, among which N136Y and Y447H are suspected to be involved in azole resistance. We suggest that the high genetic polymorphism of ERG11 must be considered in the rationale design of new azole compounds targeting lanosterol 14α-demethylase. A review of all Erg11 amino acid polymorphisms described to date is given. © 2010 Elsevier Inc. All rights reserved. Keywords: Candida albicans; ERG11; Azole drugs; Antifungal resistance; Amino acid substitutions 1. Introduction Candida albicans is responsible for a wide spectrum of clinical infections in humans, ranging from mucosal infections such as vaginitis or oropharyngeal candidiasis to potentially life-threatening systemic infections such as candidemia. Because of their safety profile and high therapeutic index, azole antifungal drugs have been used to treat Candida infections for many years, as first-line therapy, antifungal prophylaxis, or empirical or preemptive treatment. However, as a consequence of long-term exposure to azole drugs, resistance can arise. To date, at least 4 distinct mechanisms have been shown to confer azole resistance in C. albicans: i) reduced intracellular accumulation of azoles due to the overexpression of genes encoding efflux transporters belonging to the Adenosine-5'-triphosphate (ATP)-binding cassette superfamily ( CaCDR1 and CaCDR2) or major facilitator superfamily (CaMDR1); ii) genetic alterations in the ERG11 gene encoding lanosterol 14α-demethylase (CA-CYP51), the primary target of azoles; iii) overexpression of the ERG11 gene; and iv) alterations in the ergosterol biosynthetic pathway (Sanglard and Odds, 2002). Importantly, these mechanisms are often combined in clinical isolates (Cernicka and Subik, 2006; Chau et al., 2004; Coste et al., 2007; Franz et al., 1998; Goldman et al., 2004). Recently, Selmecki et al. (2006) demonstrated that azole resistance could also result from the formation of an Available online at www.sciencedirect.com Diagnostic Microbiology and Infectious Disease 66 (2010) 373 – 384 www.elsevier.com/locate/diagmicrobio ⁎ Corresponding author. Tel.: +33-2-40-41-28-66; fax: +33-2-40-41- 28-66. E-mail address: patrice.le-pape@univ-nantes.fr (P. Le Pape). 0732-8893/$ – see front matter © 2010 Elsevier Inc. All rights reserved. doi:10.1016/j.diagmicrobio.2009.11.006