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Characterization of R-plasmids coding for ampicillin resistance from Salmonella species
Abstract:
A sudden increase in the incidence of ampicillin resistance was observed among Salmonella species isolated within New Zealand in 1973--4. This increase was due mainly to the apperance and proliferation of Salmonella newington and Salmonella anatum serotypes resistant to ampicillin. The plasmid complements of 14 ampicillin-resistant S. newington and S. anatum isolates obtained from widely separated geographical areas within New Zealand between 1973 and 1974 were characterized by agarose gel electrophoresis. Each contained one or more plasmids ranging in molecular weight from 1.4 to 42 Mdal. Eleven isolates contained a self-transmissible plasmid of 33 Mdal which encoded resistance to ampicillin. After transfer to Escherichia coli, the 33 Mdal R-plasmids from each of these isolates were shown to be identical by restriction endonuclease analysis. The remaining three strains contained ampicillin R-plasmids having molecular weights of 35, 37.5 and 42 Mdal. These plasmids were shown by restriction endonuclease analysis to be related to the 33 Mdal R-plasmid. We conclude that the 33 Mdal plasmid and its derivatives were responsible for the increase in the incidence of ampicillin-resistant S. newington and S. anatum serotypes among the total Salmonella population.
Insights
A 1973-74 surge in ampicillin resistance in New Zealand Salmonella was linked to specific resistant strains. A 33 Mdal plasmid, transferable between bacteria, was identified as the primary cause of this resistance.
Area of Science:
- Microbiology
- Genetics
- Epidemiology
Background:
- Ampicillin resistance in Salmonella species presents a significant public health concern.
- Monitoring antimicrobial resistance patterns is crucial for effective treatment strategies.
Purpose of the Study:
- To investigate the cause of a sudden increase in ampicillin resistance in Salmonella isolates in New Zealand during 1973-1974.
- To characterize the plasmids responsible for ampicillin resistance in Salmonella newington and Salmonella anatum.
Main Methods:
- Agarose gel electrophoresis was used to analyze plasmid DNA from resistant Salmonella isolates.
- Plasmid transfer experiments to Escherichia coli were performed.
- Restriction endonuclease analysis was employed to compare plasmid DNA.
Main Results:
- A significant increase in ampicillin-resistant Salmonella newington and Salmonella anatum was observed.
- Eleven of fourteen isolates harbored a 33 Mdal self-transmissible plasmid encoding ampicillin resistance.
- This 33 Mdal plasmid and related derivatives were identified as the cause of the observed resistance.
Conclusions:
- The proliferation of ampicillin-resistant Salmonella serotypes was primarily driven by a specific 33 Mdal plasmid and its variants.
- Understanding plasmid-mediated resistance is essential for controlling antimicrobial resistance in bacterial populations.