Comparison of killing activity of caspofungin against Candida parapsilosis, Candida orthopsilosis and Candida metapsilosis (original) (raw)

Candida orthopsilosis and Candida metapsilosis are Candida species recently separated from Candida parapsilosis sensu stricto, replacing the formerly existing designation of C. parapsilosis groups II and III. 1 Retrospective analysis with DNA-based techniques of the formerly identified C. parapsilosis strain collections revealed that C. orthopsilosis and C. metapsilosis together account for fewer than 10% of all infections previously attributed to C. parapsilosis. 2,3 Information about antifungal susceptibilities of C. orthopsilosis and C. metapsilosis is scant. 2,3 However, based on newer data, echinocandin MICs for C. orthopsilosis and C. metapsilosis strains seem to be statistically significantly lower compared with C. parapsilosis. 3 The aim of our study was to determine the killing activity of caspofungin against C. parapsilosis, C. orthopsilosis and C. metapsilosis using time-kill methodology. We used six, three and four C. parapsilosis, C. orthopsilosis and C. metapsilosis isolates identified with DNA-based methods; 1 C. parapsilosis ATCC 22019 strain was also included for reference. Two C. parapsilosis, three C. orthopsilosis and three C. metapsilosis isolates were from an Italian collection of clinical isolates; all others were isolated in the University of Debrecen, Hungary. MICs were determined according to the CLSI (formerly the NCCLS) method as well as with its slightly modified version using antibiotic medium 3 (AM3) (Fluka), but otherwise the same experimental conditions. 4,5 The caspofungin concentration range was 0.015-8 mg/L; MICs were read after 24 h using the partial inhibition criterion. 4 Time-kill studies were performed as described previously using RPMI-1640 and AM3 in two simultaneous tests. 5 Caspofungin concentrations ranged from 0.06 to 16 mg/L in both media. Aliquots were removed at 0, 4, 8, 12, 24 and 48 h and plated onto Sabouraud dextrose agar.