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J Antimicrob Chemother. 1998 Jun;41(6):615-9.

In-vitro isolation and antifungal susceptibility of amphotericin B-resistant mutants of Aspergillus fumigatus.

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Department of Medicine, Wayne State University, Detroit, MI 48201, USA.


Aspergillus fumigatus mutants resistant to amphotericin B were selected in the laboratory following UV irradiation. A total of 18 colonies (frequency 1.8 x 10(-7)) that grew in the presence of amphotericin B (8 mg/L and 16 mg/L) on peptone yeast extract glucose agar were tested for their susceptibility to amphotericin B, nystatin, azoles, and the echinocandin L-743872. Ten of the 18 isolates showed an eight-fold rise in amphotericin B MIC (4 mg/L) compared with the susceptible parent whereas the remaining isolates showed a 16 to 32-fold rise in amphotericin B MIC (8-16 mg/L). Subculturing of three representatives from each of the groups that had MIC values of 4 mg/L and 8-16 mg/L for six cycles revealed that the resistance trait was stably expressed. All amphotericin B-resistant isolates showed a significant level of cross-resistance to nystatin but not to azoles and L-743872. Kill-curve studies with amphotericin B revealed that the killing of the resistant isolates was significantly less than that of the susceptible parent strain. These results show that amphotericin B-resistant mutants of A. fumigatus can be isolated in the laboratory following a single-step UV-induced mutagenesis and suggest that similar mechanisms could operate in nature for the emergence of resistance in clinical isolates.

[Indexed for MEDLINE]

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