title: In vitro and in vivo evaluation of L/105, a new topical intestinal rifamycin.
abstract: L/105 (4-deoxy-4'-methylpyrido [1',2'-1,2] imidazo [5,4-c] rifamycin SV; INN: Rifaximin) is a new rifamycin active in vitro against both gram-positive and gram-negative microorganisms. The activity of L/105 was comparable to that of rifampicin and, against gram-positive bacteria, higher than that of neomycin. The antibacterial activities of L/105 and rifampicin were equally affected by the highest size of inoculum used (10 cells/ml) and they were equally bactericidal against Staphylococcus aureus and Escherichia coli. The speed and the degree of development of resistance to L/105 were quite superimposable on those of neomycin. In vivo, L/105 did not show therapeutic activity by oral route in the staphylococcal infection in the mouse till the highest dosage used (10 mg/kg b.w.); under the same conditions, gentamicin was equally ineffective. After subcutaneous administration, L/105 showed therapeutic activity (ED50 = 0.46 mg/kg b.w.) practically superimposable on that of orally administered rifampicin.
mesh_terms: D000284:Administration, Oral; D000818:Animals; D001419:Bacteria / Q000187:drug effects*; D004353:Drug Evaluation, Preclinical; D004352:Drug Resistance, Microbial; D004926:Escherichia coli / Q000187:drug effects; D007267:Injections; D008297:Male; D051379:Mice; D008826:Microbial Sensitivity Tests; D009355:Neomycin / Q000494:pharmacology; D012293:Rifampin / Q000494:pharmacology; D012294:Rifamycins / Q000494:pharmacology*; D000078262:Rifaximin; D013211:Staphylococcus aureus / Q000187:drug effects
chemical_list: D012294:Rifamycins; D009355:Neomycin; D000078262:Rifaximin; D012293:Rifampin