We examined fast atom bombardment mass spectra (FAB-MS) of 29 clinical
isolates of Aspergillus, from five pathogenic species, for the presen
ce of phthioic acid anions (m/z 395.6) when grown at 37 degrees C. Pht
hioic acid was detected in only one of 12 A. fumigatus, three of nine
A. terreus and one of four A. niger isolates. Phthioic acid is unlikel
y to be a major pathogenicity determinant of Aspergillus.