Virulence attributes and genetic variability of oral Candida albicans and Candida tropicalis isolates Karen Regina Carim da Costa, 1 Joseane Cristina Ferreira, 2 Marco Aure ´ lio Sicchiroli Lavrador, 2 Marcelo Dias Baruffi 2 and Regina Celia Candido 2 1 Faculdade de Cie ˆncias Farmace ˆuticas – Universidade Federal do Amazonas, Manaus, AM, Brazil and 2 Faculdade de Cie ˆncias Farmace ˆuticas de Ribeira ˜o Preto – Universidade de Sa ˜o Paulo, Brazil Summary The wide spectrum of candidiasis and its clinical importance encourage the research with the purpose of clarifying the mechanisms of pathogenicity and identification of virulence factors of Candida sp. Therefore, the aim of this study was to verify the adhesion capacity, protease activity and genotypic diversity of oral C. albicans and C. tropicalis isolates. The adhesion ability to the extracellular matrix glycoproteins laminin and fibronectin was evaluated using the ELISA technique. The research of proteases was carried out in agar plate containing bovine albumin and through a quantitative method in buffer solution containing haemoglobin. Intra and interspecies polymorphisms was verified through random amplified polymorphic DNA (RAPD) technique. All C. albicans and C. tropicalis isolates binded to immobilised laminin and fibronectin. Ca33 and Ct13 isolates had relative adhesion index significantly higher than the other isolates for both glycoproteins (P < 0.001). Protease activity was observed in all isolates of C. albicans using either the semi-quantitative or quantitative assay. The protease activity of C. tropicalis was better detected through the quantitative assay. The genotypic diversity by RAPD revealed a heterogeneous population in both species. Nevertheless, C. tropicalis presented higher genetic variability than C. albicans strains. Key words: C. albicans, C. tropicalis, adhesion, protease activity, RAPD. Introduction Yeast belonging to the genus Candida are opportunistic pathogens and their occurrence as commensal or pathogen depends on the ability to modulate the expression of virulence factors in response to local alterations associated to the competence of the host immune system. 1 Several factors such as adhesion to the host cells, hyphae formation, phenotypic plasticity and synthesis of hydrolytic enzymes are underlying elements to the virulence. 2 Adhesion is the first step in the establishment of infection. Fungal pathogens are capable of adhering to different cellular types and of interacting with extracel- lular matrix components (ECM), which may present several sites for the fixation of microorganisms. 3,4 Laminin, fibronectin, type IV collagen, entactin and vitronectin appear to be involved in the adhesion of C. albicans. 4 The ability of Candida in the production of exoenzymes is one of the most important virulence factors. The main representatives of the exoenzymes are proteinase (Sap) and phospholipase, which have the capability of degrading the epithelia stratum corneum layer and allowing the invasion of the host tissue. 5 Of the currently available Candida genotyping tech- niques, RAPD is relatively cost-effective and matches the resolving power of electrophoretic karyotyping. These Correspondence: Prof. Dr Karen Regina Carim da Costa, Faculdade de Ci- e ˆ ncias Farmace ˆ uticas, Universidade Federal do Amazonas, Rua Alexandre Amorim, 330, 69010-300, Manaus, AM, Brazil. Tel. ⁄ Fax: +55 92 3305 5000. E-mail: krccosta@ufam.edu.br Submitted for publication 2 February 2011 Revised 10 July 2011 Accepted for publication 2 September 2011 Original article Ó 2011 Blackwell Verlag GmbH Mycoses, 2012, 55, e97–e105 doi:10.1111/j.1439-0507.2011.02125.x mycoses Diagnosis,Therapy and Prophylaxis of Fungal Diseases