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Plasmid-determined antibiotic resistance in Shigella flexneri isolated in England and Wales between 1974 and 1978
Abstract:
The majority of Shigella flexneri strains isolated in England and Wales are from infections contracted abroad. Most of these strains are drug-resistant, over 75% being resistant to streptomycin and sulphonamides, sulphonamides alone or streptomycin, sulphonamides and tetracyclines. A selection of resistant strains was tested for resistance transfer and the plasmids identified were characterized by compatibility grouping. Streptomycin and sulphonamide resistance was usually determined by a non-autotransferring plasmid which may be mobilized by standard transfer factors, or by the plasmid which conferred tetracycline resistance where this was present. The remaining resistant strains were predominantly resistant to four or more drugs. These strains carried autotransferring plasmids of a variety of compatibility groups, of which groups B, I1 and FII were the most common.
Insights
Most Shigella flexneri strains in England and Wales originate from abroad and exhibit significant drug resistance. Resistance to streptomycin and sulphonamides is common, often mediated by plasmids, with some strains showing multi-drug resistance.
Area of Science:
- Microbiology
- Infectious Diseases
- Genetics
Background:
- Shigella flexneri infections in England and Wales are frequently linked to international travel.
- A significant proportion of these isolated strains display resistance to multiple antimicrobial drugs.
Purpose of the Study:
- To investigate the antimicrobial resistance patterns of Shigella flexneri strains.
- To characterize the plasmids responsible for drug resistance and their transfer capabilities.
Main Methods:
- Antimicrobial susceptibility testing of isolated Shigella flexneri strains.
- Plasmid identification and characterization using compatibility grouping.
- Assessment of plasmid transferability.
Main Results:
- Over 75% of strains were resistant to streptomycin and sulphonamides, or streptomycin, sulphonamides, and tetracyclines.
- Streptomycin and sulphonamide resistance was often associated with non-autotransferring plasmids, mobilizable by other factors, or tetracycline resistance plasmids.
- Multi-drug resistant strains (≥4 drugs) carried autotransferring plasmids, with common compatibility groups including B, I1, and FII.
Conclusions:
- Drug resistance in Shigella flexneri strains in England and Wales is largely plasmid-mediated.
- The prevalence of transferable plasmids contributes to the spread of antimicrobial resistance.
- Understanding plasmid characteristics is crucial for managing infectious disease outbreaks.