THE EFFECT OF SOME ANTIBIOTICS ON ENTEROCOCCUS-FAECIUM SF-68 INOCULATED IN GERM-FREE MICE

A strain of Enterococcus faecium SF 68 (sensitive to penicillin, tetra cycline, virginiamicin and tylosin, but resistant to streptomycin) was administered to five groups of germ-free mice. Each group was subsequ ently given 40 mug/ml and then 80 mug/ml of a single antibiotic. The f ollowing determinations were made: a) colonization of the bacterial st rain before and after administration of the antibiotic and b) the MICs in the original strain and after administration of the antibiotic (80 mugIml). The results show that in the mice treated with streptomycin, colonization is not influenced by the antibiotic treatment; in mice t reated with antibiotics to which the strain is sensitive, the coloniza tion increases in proportion to the level of the antibiotic resistance (tylosin and tetracycline).