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Antibiotic resistance in Neisseria denitrificans
Abstract:
An ampicillin-resistant strain of Neisseria denitrificans was produced by serial passage of the organisms in media containing increased concentrations of antibiotic. The 400-fold increase in resistance obtained was a relatively stable characteristic. Ampicillin resistance in this organism was apparently related to a loss or modification of the penicillin-binding proteins associated with the cytoplasmic membranes. Membranes isolated from the ampicillin-resistant strain bound significantly less radioactive penicillin than those isolated from the parent strain and revealed one major and three minor penicillin-binding proteins. All four penicillin-binding proteins were present in reduced amounts or had a decreased capacity for penicillin binding in the ampicillin-resistant cells. The increased resistance did not involve enzymic degradation of the antibiotic or a general reduction in the permeability of the outer layers of the cell. No difference in the amount of peptidoglycan present in the parent and ampicillin-resistant cells or in the gross chemical structure of the peptidoglycans of the two strains was observed.
Insights
Researchers developed an ampicillin-resistant Neisseria denitrificans strain. This resistance stemmed from altered penicillin-binding proteins, not antibiotic degradation or permeability changes.
Area of Science:
- Microbiology
- Molecular Biology
- Antibiotic Resistance
Background:
- Neisseria denitrificans is a bacterium that can develop antibiotic resistance.
- Understanding the mechanisms of ampicillin resistance is crucial for combating bacterial infections.
Purpose of the Study:
- To generate and characterize an ampicillin-resistant strain of Neisseria denitrificans.
- To investigate the molecular mechanisms underlying ampicillin resistance in this species.
Main Methods:
- Serial passage of Neisseria denitrificans in increasing ampicillin concentrations.
- Isolation and analysis of cytoplasmic membranes.
- Penicillin-binding protein assays using radioactive penicillin.
Main Results:
- A 400-fold increase in ampicillin resistance was achieved and found to be stable.
- Resistance correlated with altered or reduced penicillin-binding proteins in cytoplasmic membranes.
- No evidence of antibiotic degradation or altered cell permeability was found.
Conclusions:
- Ampicillin resistance in Neisseria denitrificans is primarily mediated by modifications to penicillin-binding proteins.
- This resistance mechanism does not involve enzymatic inactivation of ampicillin or changes in cell wall permeability.