In vitro antimicrobial activity of the new antibiotic vermisporin

The antimicrobial activity of vermisporin, a new antibiotic produced by fermentation of the fungusOphiobolus vermisporis, was tested in vitro. Vermisporin inhibited 90 % ofBacteroides fragilis and otherBacteroides spp. at 1 µg/ml (range 0.25–1 µg/ml).Clostridium perfringens were inhibited by 1 µg/ml (range 0.25–2 µg/ml). Vermisporin inhibited 90 % ofStaphylococcus aureus, including methicillin-resistantStaphylococcus aureus, at 0.5 µg/ml (range 0.12–0.5 µg/ml). Vermisporin MICs for group A, B, C, F and G streptococci were < 1 µg/ml when tested in Haemophilus Test Medium but 8 µg/ml in the presence of blood. Vermisporin MICs forEnterobacteriaceae, Pseudomonas aeruginosa andHaemophilus influenzae exceeded 64 µg/ml. Inhibited organisms had MBCs 16- to 32-fold above the MICs.