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Studies on the development of chloramphenicol resistance in Salmonella typhimurium
Abstract:
Chloramphenicol therapy of acute and chronic Salmonella typhimurium infection in mice did not lead to the development of chloramphenicol resistant mutants of this organism. However, chloramphenicol resistant organisms were readily produced in vitro. Transfer of chloramphenicol resistance from a donor strain of Escherichia coli X12 to a suitable recipient strain of S typhimurium 5235 occurred readily in the intestine of 15 out of 20 conventional mice, following oral administration of large doses of these strains supplemented by chloramphenicol therapy. When a similar system was used in untreated animals, only a small number of chloramphenicol resistant S typhimurium were isolated from three out of 18 mice. The virulence of chloramphenicol resistant S typhimurium produced in vitro and in vivo was similar to that of the sensitive parent strain.
Insights
Chloramphenicol therapy did not induce resistance in Salmonella typhimurium in mice. However, chloramphenicol resistance transfer occurred readily in the mouse intestine when supplemented with therapy, suggesting potential for antimicrobial resistance spread.
Area of Science:
- Microbiology
- Antimicrobial Resistance
- Bacterial Genetics
Background:
- Salmonella typhimurium is a significant pathogen.
- Chloramphenicol is an antibiotic used to treat bacterial infections.
- Antimicrobial resistance is a growing global health concern.
Purpose of the Study:
- To investigate the development of chloramphenicol resistance in Salmonella typhimurium during therapy in mice.
- To examine the in vivo transfer of chloramphenicol resistance between bacterial strains in the mouse intestine.
- To assess the virulence of chloramphenicol-resistant Salmonella typhimurium.
Main Methods:
- Mice were infected with Salmonella typhimurium and treated with chloramphenicol.
- In vitro and in vivo experiments were conducted to generate and transfer chloramphenicol resistance.
- Escherichia coli strains were used as donors for resistance transfer to Salmonella typhimurium.
- Virulence of resistant and sensitive strains was compared.
Main Results:
- Chloramphenicol therapy in mice did not result in the emergence of resistant Salmonella typhimurium mutants.
- Chloramphenicol-resistant organisms were easily generated in vitro.
- Transfer of chloramphenicol resistance from Escherichia coli to Salmonella typhimurium occurred efficiently in the mouse intestine when supplemented with chloramphenicol therapy.
- Resistance transfer was significantly less efficient in untreated animals.
- Chloramphenicol-resistant Salmonella typhimurium exhibited similar virulence to the sensitive parent strain.
Conclusions:
- In vivo selection for chloramphenicol resistance in Salmonella typhimurium during therapy is unlikely.
- Chloramphenicol therapy can facilitate the horizontal transfer of resistance genes in the intestinal environment.
- The emergence and spread of antimicrobial resistance require careful consideration of antibiotic use in conjunction with potential resistance transfer.