Abstract title	Morphological changes and induction of antifungal resistance in Aspergillus fumigatus due to different CO2 concentrations
Objectives:
Aspergillosis is one of the most common opportunistic fungal diseases in immunocompromised and neutropenic patients. Aspergillus fumigatus is the most common cause of this infection. Due to changes in CO2 concentration that some pathogens face during the infection process and for understand roles of CO2 as a carbon basic, in this study the effects of variable CO2 concentration as one of the environmental factors were examine in the morphological changes and induction of antifungal resistance in A. fumigatus.





Methods:

A. fumigatus strains were cultured and incubated under the 1%, 3%, 5% and 12% of CO2 concentrations, each time in 1, 2, and 4 weeks. Control culture was maintained for 1 week without CO2 concentration. Morphological changes were investigated and antifungal susceptibility test was performed according to recommendations stated in the Clinical and Laboratory Standards Institute (CLSI) M38-A2 document. All tests of different CO2 concentrations were compared with control sample. In order to assess the stability of the developed MIC, the strains were sub-cultured for an additional 3 week in the absence of CO2 concentrations. Along the in vitro induction process, microscopic and macroscopic cultural observations as well were registered.





Results:

The results indicated morphological changes, included of shallow dark green, smooth, crisp to powdery colonies and reduced growth as macroscopic, short conidiophores, deformed vesicles and declined conidia as microscopic changes were seen. Maximum this changes observed in 1, 3, 5 and 12% of the CO2 concentration in the maximum incubation period (4 weeks). Induction of antifungal resistance of susceptible strains to itraconazole, voriconazole and amphotericin B increased after expose with 12% concentration of CO2 and 4 weeks incubation. MIC value for itraconazole, voriconazole and amphotericin B were 16 mg/ml, 1 mg/ml and 16 mg/ml, respectively. These values for control groups were 0.125 mg/ml, 0.125 mg/ml and 2 mg/ml, respectively.





Conclusion:

Different CO2 conditions exposure induced A. fumigatus morphological changes and an evident increase of MIC values as well as the development of cross-resistance with, itraconazole and voriconazole.