Compound inhibitory to Clostridium botulinum type E produced by a Moraxella species

A Moraxella strain, A-43, produced a compound inhibitory to the outgrowth of Clostridium botulinum type E spores. The inhibitor could be produced in various laboratory media, and the outgrowth of germinated spores was inhibited by a 1/10th dilution of the A-43 spent medium. Germination was not affected. Molecular weight of the inhibitor was estimated at 800 to 1,000. The inhibitor was dialyzable and could be concentrated by lyophilization. It was stable at 37, 25, and 5 C, but was 70% inactivated when heated at 65 C for 10 min. The inhibitor was not volatile and could not be vacuum-distilled at 40 C. Solutions of acids with pH values below 2.0 destroyed the activity. The A-43 inhibitor appears to be similar, in molecular weight and inhibition characteristics, to tylosin.