Synergism between efrotomycin and bottromycin.

BETTINA M. FROST, MARY E. VALIANT and EUGENE L. DULANEY Merck Institute for Therapeutic Research Rahway, New Jersey, 07065, U.S.A. (Received for publication May 26, 1979) Efrotomycin1) is a narrow spectrum antibiotic which is most active in vitro against representative species of Pasteurella, Moraxella and Corynebacterium2) . The in vivo activity, however, is much better than one would expect from the in vitro data2). Experimental test systems indicate efrotomycin has a potential in selected animal infections and as a growth permittent. For example, STUTZ et al.3) have shown efrotomycin to be effective as a growth permittant for grower swine. FOSTER and HARRIS4) have reported the drug to show promise for prophylactic control of swine dysentery in experimental infections incited by Treponema hrodysenteriae. Some antibiotics which act by inhibition of protein synthesis have been tested in our laboratory in combination with efrotomycin. This paper will be confined to experiments with combinations of efrotomycin and bottromycin5). The in vitro antibacterial activities of efrotomycin and bottromycin alone and in combination were determined as described previously2). Briefly, the surface of agar plates containing drugs were spot inoculated with 10-3 broth dilutions of 16-hour broth cultures. Growth was observed after 24 hours at 37°C. Sodium efrotomycin and the tertiarybutylamide of bottromycin were used in these experiments. The data are summarized in Table 1 which shows only the point of maximum synergy. Our use of the term synergy is in agreement with that of KERRY et al.6) The synergistic effect of the two antibiotics is apparent when at least one of the drugs is active against the test organism. Synergy, where observed, was reciprocal.