Mycotoxigenicity of clinical and environmental Aspergillus fumigatus and A. flavus isolates.

Clinical isolates of fifty strains of A. fumigatus and 30 strains of A. flavus from immmunocompromised patients from the hematological unit were analyzed for mycotoxin production and compared with the same number of environmental isolates (from soil, compost, and air). Only 9 (18%) strains of A. fumigatus produced gliotoxin in a mean concentration 2.22 mg mL-1 (range 0.5-5 mg mL-1). Aflatoxin B1 was detected in 7 (23%) isolates (range from 0.02 to 1.2 mg L-1) and aflatoxin G1 in one (3%) of clinical A. flavus isolates (0.12 mg L-1). In the group of environmental isolates, 11 (37%) were positive for aflatoxin B1 production (range from 0.02 to 1.2 mg L-1) and one for aflatoxin G1 (0.02 mg L-1). Bioautoantibiogram ("bioassay in situ") on TLC plates against Bacillus subtilis NCTC 8236 showed that only gliotoxin-producing strains have bactericidal activity of Rf values corresponding to gliotoxin. The secondary-metabolite profiles of clinical and environmental A. fumigatus and A. flavus isolates were homogeneous, except for gliotoxin production, which was detected only in the group of clinical isolates of A. fumigatus (18%).