title: Identification of a novel plasmid-encoded dihydrofolate reductase mediating high-level resistance to trimethoprim.
abstract: A Proteus mirabilis strain, isolated in South Africa, carried a 79kb transferable plasmid (pUK672) which encoded high-level resistance to trimethoprim (minimum inhibitory concentration greater than 2048 mg/l). The trimethoprim resistance was mediated by a dihydrofolate reductase which had completely different properties from any plasmid-encoded dihydrofolate reductase previously described. This enzyme has been designated type VI. The type VI enzyme is small (10,000 daltons) and is unstable in vitro. It is highly resistant to inhibition by both trimethoprim and methotrexate.
authors.affiliation: Emergent Pathogen Unit of the Medical Research Council, University of the Witwatersrand, Johannesburg, South Africa.
authors.forename: B A
authors.initials: BA
authors.lastname: Wylie
authors.forename: S G
authors.initials: SG
authors.lastname: Amyes
authors.forename: H K
authors.initials: HK
authors.lastname: Young
authors.forename: H J
authors.initials: HJ
authors.lastname: Koornhof
mesh_terms: D004352:Drug Resistance, Microbial; D010957:Plasmids; D011513:Proteus mirabilis / Q000187:drug effects* / Q000201:enzymology; D013762:Tetrahydrofolate Dehydrogenase / Q000502:physiology*; D014295:Trimethoprim / Q000627:therapeutic use*
chemical_list: D014295:Trimethoprim; D013762:Tetrahydrofolate Dehydrogenase