title: Effect of antibiotics on the human intestinal flora in mice.
abstract: Antibiotics used during selective decontamination were studied for their effect on the human intestinal flora in mice. Polymyxin B and neomycin were found to eliminate Escherichia coli from the gastrointestinal tract but did not alter total numbers of obligate anaerobes. Neomycin induced an increase of the percentage of gram-negative obligate anaerobes. Cephradine did not affect the numbers of obligate and facultative anaerobes but increased the percentage of gram-negative obligately anaerobic rods in the flora. The selective effect of polymyxin B and neomycin on the flora is accounted for by a relative insusceptibility of the anaerobic flora as compared with E. coli. Low concentrations of polymyxin B and neomycin were detected in caecal supernatants. This was found to be due to strong binding of both antibiotics to the solid fraction of intestinal contents.
mesh_terms: D000667:Ampicillin / Q000378:metabolism / Q000494:pharmacology; D000693:Anaerobiosis; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001419:Bacteria / Q000187:drug effects*; D002515:Cephradine / Q000378:metabolism / Q000494:pharmacology; D004926:Escherichia coli / Q000187:drug effects; D005243:Feces / Q000382:microbiology; D006801:Humans; D007422:Intestines / Q000382:microbiology*; D051379:Mice; D009355:Neomycin / Q000378:metabolism / Q000494:pharmacology; D011112:Polymyxin B / Q000378:metabolism / Q000494:pharmacology; D051381:Rats
chemical_list: D000900:Anti-Bacterial Agents; D000667:Ampicillin; D002515:Cephradine; D009355:Neomycin; D011112:Polymyxin B