title: Distribution of R plasmids conferring a permeability barrier to cephalosporins on bacteria isolated from clinical specimens.
mesh_terms: D000667:Ampicillin / Q000494:pharmacology; D002463:Cell Membrane Permeability; D002509:Cephaloridine / Q000378:metabolism* / Q000494:pharmacology; D003227:Conjugation, Genetic; D004755:Enterobacteriaceae / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D011815:R Factors; D001618:beta-Lactamases / Q000378:metabolism
chemical_list: D000667:Ampicillin; D001618:beta-Lactamases; D002509:Cephaloridine