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Transferable trimethoprim resistance in urinary tract pathogens isolated in Finland and Sweden
Abstract:
The incidence of trimethoprim resistance (MIC greater than 4 micrograms/ml) among urinary pathogens from inpatients was earlier shown to be 1.6-3.6% in Stockholm and 31-49% in Turku in 1977-1978. In strains from this study trimethoprim resistance could be transferred from 13/51 donor strains. Resistance to streptomycin was co-transferred in all matings but 2, and to tetracycline, ampicillin, carbenicillin and chloramphenicol in some cases. Sulphonamide resistance was co-transferred in 2 cases. In all matings but 1 at least 1 plasmid was transferred. A plasmid with similar molecular weight was transferred from 5 Turku and 4 Stockholm donor strains. Restriction enzyme digestion of this plasmid DNA showed many common bands after electrophoresis. In DNA-DNA duplex studies, using 3H-labelled Col E 1::Tn 7 as the probe, the presence of Tn 7 DNA sequences was confirmed in the 5 donor strains from Turku and 1 from Stockholm. Electrophoresis of plasmid DNA with and without digestion with restriction enzymes together with DNA-hybridization were thus useful methods to investigate the presence of genetic determinants for trimethoprim resistance in 2 areas. Other determinants than transposon Tn 7 were also present.
Insights
Trimethoprim resistance in urinary pathogens is transferable via plasmids. Genetic analysis revealed transposon Tn 7 and other resistance determinants in strains from Stockholm and Turku.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Trimethoprim resistance incidence varied significantly between Stockholm (1.6-3.6%) and Turku (31-49%) in 1977-1978.
- Urinary pathogens from inpatients exhibited varying levels of trimethoprim resistance.
Purpose of the Study:
- To investigate the transferability of trimethoprim resistance among bacterial strains.
- To identify the genetic elements responsible for trimethoprim resistance.
- To compare resistance mechanisms in strains from Stockholm and Turku.
Main Methods:
- Plasmid transfer experiments (conjugation).
- Restriction enzyme digestion and electrophoresis of plasmid DNA.
- DNA-DNA hybridization using a probe for transposon Tn 7.
- Analysis of co-transferred antibiotic resistance markers.
Main Results:
- Trimethoprim resistance was transferable from 13/51 donor strains.
- Plasmids of similar molecular weight were transferred from strains in both cities.
- Transposon Tn 7 sequences were detected in strains from both Stockholm and Turku.
- Co-transfer of resistance to streptomycin, tetracycline, ampicillin, carbenicillin, and chloramphenicol was observed.
Conclusions:
- Plasmid-mediated transfer is a significant mechanism for trimethoprim resistance dissemination.
- Both Tn 7 and other genetic determinants contribute to trimethoprim resistance.
- Molecular methods are effective for characterizing antibiotic resistance genes in different geographic locations.