Virulence of Escherichia coli strains with R-plasmid mediated penicillin resistance in mice infections
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Abstract:
Penicillinase I-, II- and III-producing R-plasmid of Escherichia coli were transferred to Escherichia coli 177, KC-14, and 444. These strains are highly virulent in mice. This study was conducted to investigate the influence of conjugative R-plasmid on the virulence of its host strains. Escherichia coli 177 after penicillinase I- or III-producing R-plasmids transfer retained parental levels of virulence. On the other hand, penicillinase II-producing transconjugants showed reduced virulence in mice. The virulence of its revertants, in which R-plasmid was eliminated by heat, were equivalent to that of the host strain. It is suggested that the decrease in the virulence of transconjugants was not due to transferred R-plasmid. The reduced virulence of the these transconjugants may be due to alterations in their components such as the lipopolysaccharides in the cell envelope.
Insights
Conjugative R-plasmids in Escherichia coli were studied for their effect on virulence. Penicillinase II-producing R-plasmids reduced bacterial virulence in mice, suggesting cell envelope alterations, not the plasmid itself, caused the change.
Area of Science:
- Microbiology
- Molecular Biology
- Pathogenesis
Background:
- Escherichia coli strains can harbor conjugative R-plasmids conferring antibiotic resistance.
- Virulence factors in bacterial pathogens are crucial for disease development.
- The impact of R-plasmid carriage on bacterial virulence is not fully understood.
Purpose of the Study:
- To investigate the influence of conjugative R-plasmids encoding penicillinase on the virulence of Escherichia coli host strains.
- To determine if R-plasmid transfer affects the pathogenicity of highly virulent E. coli strains in a murine model.
Main Methods:
- Transfer of R-plasmids encoding penicillinase I, II, and III into specific virulent Escherichia coli strains (177, KC-14, 444).
- Assessment of transconjugant virulence in mice through infection studies.
- Analysis of virulence in revertant strains where R-plasmids were eliminated.
Main Results:
- Escherichia coli strains receiving penicillinase I or III-producing R-plasmids maintained parental virulence levels.
- Transconjugants with penicillinase II-producing R-plasmids exhibited significantly reduced virulence in mice.
- Revertant strains, lacking the R-plasmid, regained virulence equivalent to the original host strain.
Conclusions:
- The reduced virulence observed in some transconjugants is unlikely to be directly caused by the transferred R-plasmid itself.
- Alterations in bacterial cell envelope components, such as lipopolysaccharides, may be responsible for the observed decrease in virulence.
- Further research is needed to elucidate the specific mechanisms underlying R-plasmid-mediated changes in bacterial pathogenicity.