Antifungal susceptibility of Aspergillusgenus determined by the Etest® method: eleven years of experience at the Instituto Médico La Floresta. Caracas, Venezuela.

Abstract

Abstract. This research aimed to determine the susceptibility of Aspergil-lus spp. to four antifungal agents using the Etest® method in several clinical samples (respiratory samples, soft tissue, otic tissue, and ocular tissue, among others) from a private health center in Venezuela. Thirty-three strains were evaluated: 11 Aspergillus section Flavi, eight Aspergillus section Fumigati, six Aspergillus section Nigri, four Aspergillus section Terrei, and four Aspergillus spp. A 0.5 McFarland standard suspension of a 5-day culture of each Aspergillusstrain was prepared on Potato Dextrose agar and then inoculated on Sabouraud agar plates with 2% glucose. Voriconazole (VCZ), amphotericin B (AMB), caspo-fungin (CAS), and posaconazole (PCZ) were tested. Minimal inhibitory concen-trations (MIC) in μg/mL were determined after 24 and 48 hours of incubation at 35 °C and th range (R), geometric mean (GM), MIC50, and MIC90 were calcu-lated. The results for the 33 Aspergillus spp. tested after 24 h were the follow-ing: VCZ (R = 0.031- 16; GM = 0.145; MIC50 = 0.125 and MIC90 = 0.5), AMB (R = 0.031-16; GM = 0.644; MIC50 = 0.5 and MIC90 = 8), CAS (R = 0.031-16; GM = 0.1076; MIC50 = 0.063 and MIC90 = 1), PCZ (R =0.031 - 0.5; GM = 0.0755; MIC50 = 0.063 and MIC90 = 0.25). This investigation allowed assessing the an-tifungal susceptibility profiles of Aspergillus spp. isolated from clinical samples by the Etest® method, which is practical, reproducible and easy to perform in microbiology laboratories.