The effect of coumermycin on experimental listeriosis.

The in vitro susceptibilities of Listeria spp. to coumermycin and novobiocin were tested. Coumermycin (0.015-0.12 mg/l) displayed lower minimum inhibitory concentrations than novobiocin (1-2 mg/l). There was only a narrow range of susceptibilities among 52 strains of Listeria spp. Bactericidal activity, however, could not be found. The in vivo activities of coumermycin were tested in mice. In normal adult mice infected with a virulent strain of L. monocytogenes the bacterial counts decreased rapidly after parenteral treatment with 2 mg twice daily but not after oral administration of 4 mg twice daily. Bacterial eradication was so effective that an immune response was prevented. Even in congenitally athymic mice a complete cure could be achieved.