In vitro antibacterial properties of EL-870, a new semi-synthetic macrolide antibiotic.

A new macrolide antibiotic, EL-870, 20-deoxo-20-(3,5-dimethylpiperidin-1-yl)desmycosin, has been prepared by chemical modification of desmycosin. In vitro, against selected animal bacterial pathogens, it inhibited growth of Pasteurella multocida, Pasteurella haemolytica, Mycoplasma hyopneumoniae, Actinobacillus pleuropneumoniae, Streptococcus suis, Actinomyces pyogenes and certain other bacteria at levels of 6.25 micrograms/ml or less. In general, the MICs for Gram-negative enteric bacteria have been greater than 50 micrograms/ml. Concentrations equivalent to 4 X the MIC value were bactericidal for Pasteurella sp. EL-870 had other antibacterial properties which were characteristic of macrolide antibiotics.