Biodiversity, virulence factors and antifungal susceptibility of clinical isolates of Candida parapsilosis sensu lato

M. Ortega-Riveros, I. Miranda-Zapico, E. Eraso, G. Quindós

Author address: 

Universidad del Paí­s Vasco, LEIOA, Spain


Candida parapsilosis is an increasing cause of invasive candidiasis. However, this species has been recently split in at least three different species Candida parapsilosis sensu stricto, and the closely related Candida orthopsilosis, and Candida metapsilosis. Differences have been reported among these species in antifungal susceptibility and virulence characteristics. Objectives: To study the biodiversity, virulence factors and antifungal susceptibility patterns in clinical isolates of Candida parapsilosis sensu lato. Methods: Twenty-two clinical isolates randomly selected from our stock collection including 14 C. parapsilosis sensu stricto, five C. metapsilosis and three C. orthopsilosis were studied. The clinical origins of isolates were blood (12 isolates), oral mucosa (3 isolates), vagina (3 isolates) and other different specimens (4 isolates). In addition, C. parapsilosis ATCC 90018 and ATCC 22019, C. metapsilosis ATCC 96143 and ATCC 96144 and C. orthopsilosis ATCC 96139 and ATCC 96141 were included as reference strains. Phenotypic switching was evaluated onto a Lee’s medium with phloxine B and only three aminoacids (lysine, valine and alanine) agar, biofilm formation on polystyrene by a colorimetric method (tetrazolium salt reduction), proteinase and phospholipase production by a plate agar method and antifungal susceptibility by Sensititre YeastOne 9 (Trek Diagnostics Systems, USA). Results: Only two strains of C. parapsilosis showed a phenotype switching in the texture and morphology of colonies. Of them, one remained morphological stable in successive subcultures. This strain, with smooth phenotype, produced a poor biofilm and showed a decreased susceptibility to caspofungin (MIC 48h= 8 μg/ml). Five out of 14 C. parapsilosis (4 with rough phenotype) were moderately producers of biofilm on polystyrene. The rest of C. parapsilosis produce a poor biofilm. Moreover, all isolates of C. metapsilosis and C. orthopsilosis were poor biofilm producers. Most isolates were susceptible to the all antifungal agents tested, but five isolates of C. parapsilosis (4 with smooth phenotype) had a decreased susceptibility to anidulafungin (MIC 48h= 4 μg/ml). However micafungin was active against all C. parapsilosis isolates. Phospholipase and proteinase activities were not detected in any of the tested isolates. Conclusions: The smooth phenotype of C. parapsilosis was less susceptible in vitro to anidulafungin. Micafungin was active against C. parapsilosis. There was no relationship between virulence factors and the anatomical origin of the strains. Biofilm formation was higher in rough strains of C. parapsilosis. Funding: Projects GIC07 123-IT-222-07 (Departamento de Educacií³n, Universidades e Investigacií³n, Gobierno Vasco), S-PE08UN35 (Saiotek 2008, Departamento de Industria, Comercio y Turismo, Gobierno Vasco) and PI061895/2006 (Fondo de Investigacií³n Sanitaria del Ministerio de Sanidad y Consumo de Espaí±a).

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Full conference title: 

4th Trends in Medical Mycology
    • TIMM 4th (2012)