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R-plasmid transfer in vivo in the absence of antibiotic selection pressure
Abstract:
The persistence of an O18 Escherichia coli strain resistant to tetracycline, streptomycin, and sulfonamide has been followed in the fecal flora of a single individual over a period of 9 months. The strain in question carrying an R plasmid was detectable from the beginning of the survey, but it was only after a 10-day period of tetracycline therapy that it reached an all but permanent dominance in the fecal flora. No transfer of the R plasmid carried by the strain to any other coliform could be detected for 202 days after the end of tetracycline treatment. At this point, however, an O88 E. coli carrying the same plasmid as the O18 strain appeared briefly as a predominant component of the flora. The two plasmids isolated from the O18 and the O88 E. coli strains have been characterized in molecular terms and found to be similar. This suggests that R-plasmid transfer between two E. coli strains occurred in an individual who was living a normal daily life and who was not receiving antibiotics.
Insights
An O18 Escherichia coli strain carrying an R plasmid became dominant after tetracycline therapy. Later, an O88 E. coli strain with a similar R plasmid appeared, suggesting in-vivo transfer without antibiotics.
Area of Science:
- Microbiology
- Genetics
- Epidemiology
Background:
- Antibiotic resistance is a growing public health concern.
- R plasmids mediate resistance in bacteria like Escherichia coli.
- Understanding R plasmid dynamics in the gut microbiome is crucial.
Purpose of the Study:
- To track the persistence and transfer of an R plasmid within an individual's fecal flora.
- To investigate the potential for R plasmid transfer between Escherichia coli strains in vivo.
- To characterize the molecular similarity of R plasmids in different E. coli strains.
Main Methods:
- Longitudinal fecal sampling over 9 months.
- Detection and isolation of specific Escherichia coli strains (O18 and O88).
- Molecular characterization of isolated R plasmids.
Main Results:
- An O18 E. coli strain with an R plasmid achieved dominance after tetracycline treatment.
- No R plasmid transfer was detected for 202 days post-treatment.
- An O88 E. coli strain with a similar R plasmid emerged, indicating potential in-vivo transfer.
- Molecular analysis confirmed similarity between the R plasmids from O18 and O88 strains.
Conclusions:
- R plasmid transfer between E. coli strains can occur in the human gut without ongoing antibiotic pressure.
- The human gut microbiome can facilitate horizontal gene transfer of antibiotic resistance.
- This study highlights the complex dynamics of R plasmid persistence and dissemination in vivo.