In Vitro Susceptibilities of Aspergillus Species to Triazoles and Amphotericin B
Objective: to identify the efficacy of certain antifungal agents against different Aspergillus species and the development of acquired resistance.
Methods: A total of 177 clinical isolates of different Aspergillus spp. were obtained from different medical centers in Baghdad. In vitro susceptibility tests are based on the measurement of the fungal growth in the presence of different drug concentrations (Posaconazole, voriconazole, itraconazole and amphotericin B) so as to determine the minimum inhibitory concentration (MIC) of antifungals. The broth microdilution (BMD) method was performed according to the CLSI M38-A2 standard.
Results: MIC(μg/ml) distribution for azoles and amphotericin B with different Aspergillus species were as follows: A. fumigatus, amohptericin B, 1 ; itraconazole, 0.5 ; voriconazole, 0.25 ; posaconazole, 0.06 ; A.flavus, amohptericin B, 1 ; itraconazole, 0.5 ; voriconazole, 0.5; posaconazole, 0.125 ; A. niger, amohptericin B, 1 ; itraconazole, 1 ; voriconazole, 0.5 ; posaconazole, 0.25 ; A. terreus, amohptericin B, 2 ; itraconazole, 0.5 ; voriconazole, 0.5 ; posaconazole, 0.25 and A. versicolor, amohptericin B, 2 ; itraconazole, 1 ; voriconazole, 0.5 ; posaconazole, 0.5. 7.8% of A. fumigatus, 17.4% of A. flavus and 26.6% of A. terreus showed in vitro resistance to amphotericin B. 4.3% of A. fumigatus had resistance to itraconazole, with cross resistance to posaconazole observed in 80%.
Conclusion: Triazoles and amphotericin B have good in vitro activities against most Aspergillus species in the following order: posaconazole, voriconazole, itraconazole and amphotericin B. Majority of Aspergillus species exhibited in vitro resistance to amphotericin B followed by itraconazole and there was cross resistance between itraconazole and posaconazole, but not between itraconazole and voriconazole.