Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.5.1.3 (dihydrofolate reductase)
 5,819 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In a recent survey of trimethoprim resistance, 357 Gram-negative aerobic organisms were isolated from healthy volunteers from rural and urban populations in South Africa. Trimethoprim resistance did not transfer to an Escherichia coli J62-2 recipient strain by conjugation in a liquid mating in 161 (45.1%) of the isolates. These isolates which did not transfer their resistance were probed with intragenic oligonucleotide probes for the types Ia, Ib, IIIa, V, VI, VII, VIII, IX, X and XII dihydrofolate reductase genes. Contrary to all previous data, the most prevalent dihydrofolate reductase gene in this group of non-transferable isolates which hybridized, was the type VII (38%) followed by the type Ia (25%), Ib (12%), V (1.7%) and VIII (1.2%). None of the strains hybridized to the types IIIa, VI, XI, X and the XII dihydrofolate reductase probes. Southern blots of plasmid and chromosomal DNA from selective isolates revealed that the type VII dihydrofolate reductase genes were located on the chromosome and were associated with the integrase gene of Tn21. However, the type Ib and V dihydrofolate reductase genes were all found on plasmids which could not be mobilized. The type Ia dihydrofolate reductase genes were found on both non-transferable plasmids and on the chromosome. The nature of the genetic structures associated with a dihydrofolate reductase gene strongly affects the means of spread of the gene in a population.
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PMID:Prevalence and genetic location of non-transferable trimethoprim resistant dihydrofolate reductase genes in South African commensal faecal isolates. 758 65

In a recent survey of trimethoprim resistance, 357 Gram-negative aerobic organisms were isolated from healthy volunteers from rural and urban populations in South Africa. Trimethoprim resistance was transferable in 184 (52%) of the isolates. A further 12 (3%) transferred in the presence of an X+ actor. The transconjugants were probed with intragenic oligonucleotide probes for the type Ia, Ib, IIIa, VIII, V, VI, VII, IX, X and XII dihydrofolate reductase genes. Contrary to all previous data, the most prevalent dihydrofolate reductase gene was the type Ib (30%) followed by the type VIII (23%), V (13%), Ia (6%), VII (3%), and XII (0.5%). None of the strains hybridised to the type IIIa, XI, X and the VI dihydrofolate reductase probes. Plasmid restriction profiles revealed that the high prevalence of the type Ib and VIII dihydrofolate reductase genes resulted from the presence of ubiquitous plasmids. These results highlight the previous problems associated with the distinction of closely related dihydrofolate reductase genes.
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PMID:Prevalence of trimethoprim resistant dihydrofolate reductase genes identified with oligonucleotide probes in plasmids from isolates of commensal faecal flora. 762 84

An uncommon dihydrofolate reductase (DHFR), type IIIc, was coded for by Shigella sonnei that harbors plasmid pBH700 and that was isolated in North Carolina. The trimethoprim resistance gene carried on pBH700 was subcloned and sequenced. The nucleotide sequence of the gene encoding type IIIc DHFR was identical to the gene encoding type VIII DHFR. The type IIIc amino acid sequence was approximately 50% similar to those of DHFRs commonly found in enteric bacteria. Furthermore, this gene was flanked by IS176 (IS26), an insertion sequence usually associated with those of aminoglycoside resistance genes. The gene for type IIIc DHFR was located by hybridization within a 1,993-bp PstI fragment in each of eight conjugative plasmids from geographically diverse strains of S. sonnei. Each plasmid also conferred resistance to ampicillin, streptomycin, and sulfamethoxazole and belonged to incompatibility group M. Plasmids carrying this new trimethoprim resistance gene, which is uniquely associated with IS176, have disseminated throughout the United States.
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PMID:Sequence identity with type VIII and association with IS176 of type IIIc dihydrofolate reductase from Shigella sonnei. 769 91