additions of aureomycin and chloramphenicol to various fungal agar media to prevent bacterial contamination

Isolating fungi from soil, diseased plant parts, and contaminated foods and fabrics is difficult when bacteria are present. Aureomycin and chloramphenicol (100 ppm each) added to several agar media completely negated bacterial contamination but not fungal growth. Control cultures (no antibiotics) were contaminated with bacteria often preventing fungal counts and isolations. Soil dilution plates (>1500) never yielded bacterial colonies and counts compared favorably to acidified agar cultures (pH 3.5). Fungi isolated from the antibiotic media exhibited no apparent morphological anomalies although growth of selected fungi (liquid culture) was initially retarded. Recent studies indicate that lower concentrations of the antibiotics (35 to 50 ppm each) will also suppress bacterial growth.