title: Molecular characterization of "plasmid-free" antibiotic-resistant Haemophilus influenzae.
abstract: We examined 14 multiresistant and 8 ampicillin- or tetracycline-resistant Haemophilus influenzae isolates and 4 ampicillin-resistant H. parainfluenzae isolates for plasmid deoxyribonucleic acid. Sixteen strains carried plasmids. Both "plasmid-free" and plasmid-carrying isolates transferred the antibiotic resistance by conjugation. All transconjugants carried plasmid deoxyribonucleic acid, suggesting that the apparent plasmid-free strains contained R plasmids encoding for antibiotic resistance.
mesh_terms: D000667:Ampicillin / Q000494:pharmacology; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D003227:Conjugation, Genetic; D006190:Haemophilus / Q000187:drug effects* / Q000235:genetics; D006193:Haemophilus influenzae / Q000187:drug effects* / Q000235:genetics; D011815:R Factors; D013752:Tetracycline / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D000667:Ampicillin; D013752:Tetracycline