title: Streptococcus faecalis: in vitro susceptibility to antimicrobial drugs, single and combined, with and without defibrinated human blood.
abstract: Ampicillin, fusidic acid, gentamicin, imipenem, mezlocillin, ofloxacin, penicillin G, piperacillin, and vancomycin were examined for inhibitory and bactericidal activity in various broth media against 7 clinical isolates of Streptococcus faecalis. On a weight-for-weight basis, ampicillin, imipenem, mezlocillin, and ofloxacin proved to be more efficacious. All enterococcal isolates were resistant against gentamicin; fusidic acid and vancomycin lacked bactericidal activity. The combinations of either ampicillin, imipenem, mezlocillin, ofloxacin, piperacillin, or vancomycin with a subinhibitory concentration (4 micrograms/ml) of gentamicin, with or without added 65% (v/v) fresh defibrinated human blood, respectively, yielded additive effects against all enterococcal isolates. The addition of fresh human blood failed to enhance the antienterococcal activity of 4 micrograms/ml of gentamicin; in contrast, addition of 65% (v/v) fresh or heat-inactivated (56 degrees C, 30 min) normal rabbit, bovine, and human sera augmented the activity of gentamicin, an effect that was ablated through the addition of either 0.005 M DTT or 0.01 M MgCl2 + 0.01 M EGTA + 0.01 M CaCl2, supplements known to antagonize human serum beta-lysin, but not lysozyme activity.
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001769:Blood; D002417:Cattle; D013293:Enterococcus faecalis / Q000187:drug effects*; D005337:Fibrin / Q000502:physiology; D005672:Fusidic Acid / Q000494:pharmacology; D005839:Gentamicins / Q000494:pharmacology; D006801:Humans; D015378:Imipenem; D008826:Microbial Sensitivity Tests; D015242:Ofloxacin; D010078:Oxazines / Q000494:pharmacology; D010406:Penicillins / Q000494:pharmacology; D011817:Rabbits; D013845:Thienamycins / Q000494:pharmacology; D014640:Vancomycin / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D005839:Gentamicins; D010078:Oxazines; D010406:Penicillins; D013845:Thienamycins; D005672:Fusidic Acid; D014640:Vancomycin; D015378:Imipenem; D005337:Fibrin; D015242:Ofloxacin