Novel type of plasmid-borne resistance to trimethoprim

Sundström, Lars; Vinayagamoorthy, T.; Sköld, Ola

doi:10.1128/aac.31.1.60

Cited by 43 publications

(46 citation statements)

References 32 publications

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“…Resistant strains were mated with E. coli K-12 strain C600 (supE44 hsdR thi-1 thr-1 leuB6 lacY1 tonA21 Nal r Fu r ) to determine if resistance markers were conjugatable (27). Transconjugants were selected on plates containing nalidixic acid (40 mg/liter) (Sigma Chemical Company, St. Louis, Mo.)…”

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Antibiotic-Resistant Cell-Detaching Escherichia coli Strains from Nigerian Children

et al. 2002

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The properties of 23 cell-detaching Escherichia coli strains that were isolated from stool specimens in Nigeria are described. Common properties of the strains included the presence of genes encoding ␣-hemolysin (100%), pyelonephritis-associated pili (100%), and cytotoxic necrotizing factor 1 (70%) as well as lactose negativity (70%) and multiple antibiotic resistance (74%). Antibiotic resistance was shown in most cases to be transferable and associated with the presence of class 1 integrons. Phenotypic properties and pulsed-field gel electrophoresis analysis demonstrated that the majority of the strains, particularly multiply resistant, lactosenegative O4:H40 strains, were closely related. Multiply-resistant cell-detaching E. coli strains may represent an important reservoir for antibiotic resistance genes.

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Antibiotic-Resistant Cell-Detaching Escherichia coli Strains from Nigerian Children

et al. 2002

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“…The dhfrV gene was first characterized in strains from Sri Lanka [41] and the region where these strains were collected is close to Sri Lanka. Other studies in which the dhfrV has been frequently found have also shown some association with this part of Asia.…”

Section: Discussionmentioning

confidence: 99%

“…Colony blotting was performed by the method described by Sundstrom and colleagues [41]. The probes for the various dhfr genes, used to identify the trimethoprim resistance mechanisms, and the transposon and integron open reading frames (ORFs), are as outlined in Table 1.…”

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confidence: 99%

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Trimethoprim resistant dihydrofolate reductases in normal faecal flora isolated in India

Tait

Amyes

1994

Epidemiol. Infect.

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SUMMARYA high incidence of resistance to trimethoprim has been shown in the normal faecal flora in a population in south India. The dihydrofolate reductase (dhfr) genes mediating transferable resistance to trimethoprim have been identified.Unusually, in this study, the dhfrV was shown to be the predominant resistance gene (dhfrV 50 % of transconjugants, dhfrla 30%), the dhfrlb was also detected being distinguished from the dhfrV by an oligo-probe. However, when nontransferable resistance was considered, the dhfrIa was the most prevalent of the dhfrs identified. All those plasmids harbouring the dhfrla were shown to possess Tn7. All the plasmids that probed positive for the dhfrV and the dhfrlb were shown to be associated with the integrase of the Tn2l-like transposons, but 8 of the dhfrV genes were not associated with the Tn2l resolvase. The dhfrIV was shown to be present in all seven plasmids that produced low level trimethoprimresistance. The dhfrV, first characterized in Sri Lanka, would seem to have a local distribution in this region of Asia but is distinguishable from the dhfrlb only by the use of an oligo-probe.

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“…Surveys from Sri Lanka [33] and South Africa [19] showed there to be a low prevalence of the type Ia DHFR. A study of commensal flora from South India showed that the most prevalent DHFR was the type V [34].…”

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Prevalence and genetic location of non-transferable trimethoprim resistant dihydrofolate reductase genes in South African commensal faecal isolates

et al. 1995

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SUMAIARYIn 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, Illa, 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%), lb (12%), V (1-7%) and VIII (1-2%). None of the strains hybridized to the types Illa, 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 Tn2l. However, the type lb and Vr dihydrofolate reductase genes were all found on plasmids which could not be mobilized. The type Ia dihydrofolate reductase genes were found on both nontransferable 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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Novel type of plasmid-borne resistance to trimethoprim

Cited by 43 publications

References 32 publications

Antibiotic-Resistant Cell-Detaching Escherichia coli Strains from Nigerian Children

Antibiotic-Resistant Cell-Detaching Escherichia coli Strains from Nigerian Children

Trimethoprim resistant dihydrofolate reductases in normal faecal flora isolated in India

Prevalence and genetic location of non-transferable trimethoprim resistant dihydrofolate reductase genes in South African commensal faecal isolates

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