title: Plasmid-linked ampicillin resistance in haempohilus influenza type b.
abstract: Four ampicillin-resistant, beta-lactamase-producing strains of Haempohilus influenzae type b were examined for the presence of plasmid deoxyribonucleic acid (DNA). Three resistant strains contained a 30 x 10-6-dalton (30Mdal) plasmid and one resitant strain contained a 3-Mdal plasmid. The ampicillin-sensitive Haemophilus strains examined did not contain plasmid DNA. Transformation of a sensitive H. influenzae strain to ampicillin resistance with isolated plasmid DNA preparations revealed that the structural gene for beta-lactamase resided on both plasmid species. DNA-DNA hybridization studies showed that the 30-Mdal Haemophilus plasmid contained the ampicillin translocation DNA segment (TnA) found on some R-factors of enteric origin of the H. influenzae plasmids.
mesh_terms: D000667:Ampicillin / Q000494:pharmacology*; D001433:Bacteriolysis; D002499:Centrifugation, Density Gradient; D004247:DNA / Q000032:analysis; D004996:Ethidium; D005111:Extrachromosomal Inheritance; D006193:Haemophilus influenzae / Q000276:immunology*; D008854:Microscopy, Electron; D009693:Nucleic Acid Hybridization; D010400:Penicillin G / Q000378:metabolism; D010403:Penicillin Resistance; D010405:Penicillinase / Q000032:analysis; D010957:Plasmids; D014170:Transformation, Genetic; D014316:Tritium; D014461:Ultracentrifugation
chemical_list: D014316:Tritium; D000667:Ampicillin; D004247:DNA; D010405:Penicillinase; D004996:Ethidium; D010400:Penicillin G