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Prolonged stability of R plasmids KR61 and KR61-A in Salmonella host
Indian Journal of Experimental Biology
|April 1, 1995
Summary
Two R plasmids, KR61 and KR61-A, remained stable and retained antibiotic resistance and transferability in Salmonella typhimurium LT2 for over 22 years. These R plasmids demonstrate long-term stability and conjugal transfer capabilities, even when mobilized.
Area of Science:
- Microbiology
- Genetics
- Molecular Biology
Background:
- R plasmids are crucial for antibiotic resistance dissemination in bacteria.
- The long-term stability and conjugal transferability of R plasmids are key factors in their persistence and spread.
- Understanding plasmid stability is essential for combating antimicrobial resistance.
Purpose of the Study:
- To investigate the long-term stability and conjugal transferability of two R plasmids, KR61 and KR61-A, in Salmonella typhimurium LT2.
- To assess the maintenance of antibiotic resistance profiles and transfer functions over an extended period.
- To examine the mobilization of a non-conjugative plasmid (KR61-A) by a conjugative plasmid (KR61).
Main Methods:
- Cultivation of R plasmids KR61 and KR61-A in Salmonella typhimurium LT2 on antibiotic-free media for 22 years.
- Assessment of plasmid stability by monitoring antibiotic resistance (kanamycin, neomycin, streptomycin, tetracycline, ampicillin).
- Conjugal transfer experiments to evaluate plasmid transferability and mobilization between bacterial hosts (Escherichia coli, Salmonella).
Main Results:
- Both R plasmids, KR61 (KmNmSmTc) and KR61-A (Ap), demonstrated remarkable stability in S. typhimurium LT2 for 22 years without antibiotic selection.
- Plasmid KR61 retained its conjugal transferability (RTF) and successfully transferred to new hosts.
- Plasmid KR61-A, lacking RTF, was mobilized by KR61, leading to the transfer of ampicillin resistance and co-transfer of both plasmids in various patterns.
Conclusions:
- R plasmids KR61 and KR61-A exhibit exceptional long-term stability and maintain their antibiotic resistance and transfer functions in a host bacterium over decades.
- The study highlights the potential for stable R plasmids to persist and spread resistance genes within bacterial populations.
- Mobilization of non-conjugative plasmids by conjugative ones is an effective mechanism for disseminating antibiotic resistance.