Sensibilidad in vitro de Paracoccidioides brasiliensis frente a los antifúngicos de uso sistémico

Abstract

In 1992, the NCCLS proposed a broth macrodilution method for determining the in vitro susceptibility of yeast. However, for dimorphic fungi no standardised method is available. The aim of our study was to evaluate the reference broth macrodilution method with isolates of Paracoccidioides brasiliensis. The in vitro susceptibility of two ATCC strains (32069 and 36324) and nine clinical isolates were determined against serial dilutions of amphotericin B (AMB), ketoconazole (KTZ), and itraconazole (ITZ) from 0.02 to 20 mg/l and fluconazole (FCZ) from 0.1 to 100 mg/l. The inoculum used was 0.5 x 10(4)-2.5 x 10(5) CFU/ml, employing the yeast phase in order to obtain homogeneous growth. The test was incubated with agitation in a rotating shaker at 35 degrees C, and 7 days was the optimal time for MIC final reading. Average MIC50/MIC90 (mg/l) for the eleven isolates tested were the following: AMB: < 0.02/0.16, FCZ: 1.6/6.2, KTZ: 0.08/0.31, ITZ: 0.31/1.3. One clinical isolate showed high MIC for azole drugs (KTZ: 1.3 mg/ml, FCZ: 100 mg/l and ITZ 5 mg/l). Although further studies are necessary to evaluate the usefulness of this methodology for P. brasiliensis, the latter may be clinically useful to predict the development of resistance.