Sensitivity to 5-fluorocytosine and virulence for mice of some human isolates of Aspergillus.

The sensitivity of 5-Fluorocytosine (5-FC) and the virulence for mice was assessed for 16 human isolates of Aspergillus: A. fumigatus 2, A. niger 7, A. flavus 4, A. terreus 2 and A. conicus (A. restrictus group) 1. Fourteen strains were recovered from ear exsudates, 1 from sputum and 1 from the pus of mastoid cells of an autopsy case with meningeal and cerebral involvement. Nine of them, which included strains of A. fumigatus and A. niger were sensitive to 5-FC (M.I.C. less than or equal to 6.4 microgram/ml) whereas strains of A. flavus and A. terreus were resistant (M.I.C. greater than 51.2 microgram/ml). Cultures of A. fumigatus, A. flavus and A. conicus proved to be the most virulent for mice and A. terreus strains the less virulent. Results observed with the strain of A. conicus deserves further investigations.