title: The nature of resistance to penicillins mediated by R-factor.
mesh_terms: D000667:Ampicillin / Q000494:pharmacology; D002463:Cell Membrane Permeability; D004926:Escherichia coli / Q000187:drug effects*; D008826:Microbial Sensitivity Tests; D010400:Penicillin G / Q000494:pharmacology; D010403:Penicillin Resistance; D010405:Penicillinase / Q000032:analysis / Q000378:metabolism*; D012475:Salmonella / Q000187:drug effects* / Q000201:enzymology; D012486:Salmonella typhimurium / Q000187:drug effects / Q000201:enzymology
chemical_list: D000667:Ampicillin; D010405:Penicillinase; D010400:Penicillin G