(n)an antibiotic (trade name Erythrocin or E-Mycin or Ethril or Ilosone or Pediamycin) obtained from the actinomycete Streptomyces erythreus; effective against many Gram-positive bacteria and some Gram-negative, Syn.E-Mycin, Ilosone, Ethril, Erythrocin, Pediamycin