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Origin of Haemophilus influenzae R factors
Abstract:
The Haemophilus influenzae R plasmids specifying resistance against one, two, or three antibiotics which have emerged in different parts of the world were shown to have closely related but not identical plasmid cores. The gene for ampicillin resistance in the H. influenzae plasmid pKRE5367 is part of a transposon similar to Tn3, which was transposed from pKRE5367 onto RSF1010 in Escherichia coli. An indigenous H. influenzae plasmid (pW266) was isolated. Its properties correspond to those of the H. influenzae R plasmids, except for the presence of a drug resistance transposon. The in vitro-generated H. influenzae R plasmids carrying an ampicillin resistance transposon, a tetracycline resistance transposon, and a transposon for combined tetracycline-chloramphenicol resistance resembled the natural isolates. The findings support the hypothesis that the R plasmids of H. influenzae are of multiclonal evolutionary origin.
Insights
Haemophilus influenzae R plasmids show related but distinct cores, suggesting a multiclonal origin. Antibiotic resistance genes are carried on transposons, similar to those found in natural isolates.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Antibiotic resistance in Haemophilus influenzae is a growing concern.
- R plasmids play a crucial role in the dissemination of antibiotic resistance genes.
Purpose of the Study:
- To investigate the evolutionary origins of Haemophilus influenzae R plasmids.
- To compare the genetic structures of R plasmids from different geographical locations.
Main Methods:
- Plasmid isolation and characterization.
- Transposon analysis.
- In vitro generation of R plasmids.
Main Results:
- Haemophilus influenzae R plasmids share closely related but not identical plasmid cores.
- Ampicillin resistance genes are located within Tn3-like transposons.
- In vitro generated plasmids mimic the genetic makeup of natural isolates.
Conclusions:
- The findings support a multiclonal evolutionary origin for Haemophilus influenzae R plasmids.
- Transposon-mediated gene transfer is a key mechanism in the emergence of antibiotic resistance.