Antibiotic resistance among enterococci isolated from clinical specimens between 1953 and 1954.

Two hundred twenty group D streptococci isolated from 1953 to 1954 from patients in the Washington, D.C., area were characterized. All were susceptible to ampicillin, vancomycin, and gentamicin; none produced beta-lactamase activity. High-level resistance to streptomycin was expressed by 117 strains, and 2 strains were resistant to >8 microg of chloramphenicol per ml. Three isolates were resistant to both erythromycin and lincomycin, and DNA from these hybridized to an ermAM probe. Of 118 strains resistant to tetracycline and minocycline, genomic DNA from 63 was examined for homology to tet(M), tet(O), and tet(S). DNA from 20 strains hybridized to tet(M), DNA from 37 strains hybridized to tet(S), and DNA from none of the strains hybridized to tet(O).