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A possible role of R plasmids in bacterial permeability for beta-lactam antibiotics
Abstract:
Four strains of clinical isolates of Serratia marcescens (13039, 13090, 13093, 14093) harboring R plasmids were highly resistant to ampicillin (ABPC) and cephaloridine (CER). With elimination of R plasmids from these strains by acriflavine treatment, ABPC-resistance levels of these strains were markedly reduced. Reduction of CER-resistance levels was also demonstrated in strains 13039 and 13093, but not in strains 13090 and 14093. The permeability of the former strains for CER was also decreased, but not in the latter strains. At the same time, beta-lactamase activity of these strains also almost completely disappeared when the R plasmids were eliminated. By broth matings with these strains. The recipient strains of S. marcescens 13031 (rif), Escherichia coli K-12 (rif), and E coli 15046 (rif) all acquired a high permeability barrier against CER with inheritance of the R plasmids from strains 13039 and 13093, but not from strains 13090 and 14093. The transconjugant of strain 13031 that inherited R plasmid 13093 was resistant not only to CER but also to cefazolin, cephalothin, and cephalexin. Its permeability to these antibiotics was significantly lower than that of the original strain. This fact suggest the possibility that the R plasmid from strain 13093 may be involved not only in production of beta-lactamases, but also in regulation of bacterial permeability for cephalosporins.
Insights
R plasmids in Serratia marcescens contribute to resistance against ampicillin and cephaloridine by increasing beta-lactamase activity and reducing bacterial permeability. Elimination of these plasmids reversed these effects, suggesting R plasmids regulate both factors.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Clinical isolates of Serratia marcescens exhibit high resistance to ampicillin and cephaloridine due to R plasmids.
- R plasmids are known to confer antibiotic resistance through various mechanisms.
Purpose of the Study:
- To investigate the role of R plasmids in the resistance of Serratia marcescens to ampicillin and cephaloridine.
- To determine if R plasmids influence bacterial permeability and beta-lactamase activity.
Main Methods:
- Elimination of R plasmids using acriflavine treatment.
- Assessing antibiotic resistance levels and bacterial permeability to cephaloridine.
- Conjugation experiments to transfer R plasmids to recipient strains.
- Measuring beta-lactamase activity.
Main Results:
- Elimination of R plasmids reduced ampicillin and cephaloridine resistance and beta-lactamase activity.
- R plasmids from strains 13039 and 13093 conferred resistance and reduced permeability to cephaloridine in recipient strains.
- R plasmid 13093 also conferred resistance to other cephalosporins and decreased permeability.
Conclusions:
- R plasmids in Serratia marcescens are involved in beta-lactamase production.
- R plasmids may also play a role in regulating bacterial permeability to cephalosporins.
- This suggests a dual mechanism of antibiotic resistance conferred by R plasmids.