In-vitro susceptibility of Aspergillus species isolated from cutaneous and visceral lesions to antifungal agents

Different studies have shown that despite the expanding number of antifungal agents, death rate caused by Aspergillus species has been increased during the recent decades due to drug-resistance occurrence, increased minimum inhibitory concentration (MIC) and cross-resistance among the isolated species. Regarding the lack of effective response to conventional treatments and antifungal susceptibility patterns of the most common isolated Aspergillus species, this study was undertaken to draw a clearer picture in the Iranian setting.

During 13 months from September 2009 to October 2010, 50 clinically isolated Aspergillus cases were identified based on the method described by Klich (2002) and their morphological features. Subsequently, their susceptibility test was carried out according to NCCLS- M38A broth microdilution method.

We found that 7.5% of the isolated A. flavus with an MIC>2 µg/ml to amphotericin B were probably clinically resistant types, and 25% of them with an MIC<8 µg/ml to itraconazole were less sensitive isolated species. The isolates were less sensitive to voriconazole too. The MIC range of 9 strains of A. niger and the MIC of one strain of A. fumigatus had increased to all the three medications in comparison with similar foreign studies.

In this study we found that the MICs of most isolates were in the range of the reference strains and the MICs of some isolates were in the range of similar foreign studies. In some significant cases, the MICs were beyond the known ranges showing the lower sensitivity of Iranian isolates and their increased MIC patterns.