title: Rapid microassays for clindamycin and gentamicin when present together and the effect of pH and of each on the antibacterial activity of the other.
abstract: Gentamicin was measured in the presence of clindamycin by using as the assay organism a strain of Staphylococcus aureus that was resistant to clindamycin; clindamycin was measured in the presence of gentamicin by using Clostridium perfringens as the assay organism. Both assays were in agar diffusion systems, were rapid (2 to 4 h), and had errors of less than 10%. Neither antibiotic antagonized or synergized with the other against a variety of organisms. The pK of clindamycin was 7.3, and the pK of gentamicin was 8.2. Gentamicin was 100 or more times as active in alkaline medium against both gram-positive and gram-negative organisms, but clindamycin showed a striking pH effect on activity only with gram-positive organisms.
authors.forename: L D
authors.initials: LD
authors.lastname: Sabath
authors.forename: I
authors.initials: I
authors.lastname: Toftegaard
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002981:Clindamycin / Q000494:pharmacology*; D003016:Clostridium perfringens / Q000187:drug effects; D004359:Drug Therapy, Combination / Q000494:pharmacology*; D005839:Gentamicins / Q000494:pharmacology*; D006863:Hydrogen-Ion Concentration; D008826:Microbial Sensitivity Tests
chemical_list: D000900:Anti-Bacterial Agents; D005839:Gentamicins; D002981:Clindamycin