Study of Susceptibility to Posaconazole (POS) and Caspofungin (CAS) in Invasive Yeast Strains (IYS) Isolated from Blood Cultures and CSF During Two Years in a Spanish University Hospital: Evaluation of the POS and CAS Etest.


Author address: 

Complejo Hosp. Juan Canalejo, La Coruña, Spain.


Background: It is important, following the introduction of new antifungal drugs such as POS and CAS, to monitor changes in the antifungal susceptibility of relevant pathogens. The main objective of the present work was to assess the activity of POS and CAS against a collection of yeast strains associated with invasive infections (IYS). In addition, we determined the level of concordance between the MICs obtained using the approved CLSI method and Etest (AB Biodisk). Methods: MIC determination: 53 yeast isolates (21 Candida albicans, 12 C. parapsilosis, 4 C. tropicalis, 3 C. glabrata, 3 C. guilliermondii, 2 C. krusei, 3 Rhodotorula sp. 3 Cryptococcus neoformans, 1 C. dubliniensis, 1 C. rugosa) were recovered from blood and CSF at our hospital (516,000 population assisted) from 2002-2003. MICs were performed according to M27-A2 document. E-test measurements were performed on the same group of isolates following the manufacturer's instructions; and eight additional yeast strains with high MIC values to fluconazole were included to increase the range of MICs. CLSI and E-test MICs were read at 48 and 24 h, respectively; strains that did not grow at 24 h were read at 48 h. Agreement between the methods was defined as MICs +/- 2 dilutions; a minor error was defined as +/- 3 dilutions. Results: MIC50/90 values for POS and CAS against this collection of IYS were 0.6/2 μg/mL and 1.4/8 μg/mL, respectively. The agreement between CSLI and Etest was 69% for POS and 84% for CAS; by including minor errors agreement was 87% and 90% for POS and CAS, respectively. Conclusions: The MIC values for POS and CAS against IYS are low suggesting that resistance is not an issue in our area. Regarding E-test, overall good agreement was obtained for both POS and CAS. Discrepancies for POS were primarily limited to C. albicans (this was probably due to the trailing effect) and to poorly growing strains that required incubation for 48 h.

abstract No: 


Full conference title: 

46th Interscience Conference on Antimicrobial Agents and Chemotherapy
    • ICAAC 46th