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Observations on the tolerance and the paradoxical effect in enterococci
M Puntorieri1, A Primavera, O Privitera
1Institute of Microbiology, University of Catania, Italy.
Journal of Chemotherapy (Florence, Italy)
|December 1, 1994
Summary
Enterococci exhibit unique resistance to penicillin due to altered penicillin-binding proteins (PBP). This study explores beta-lactam activity, revealing a "paradoxical effect" in certain bacterial strains and growth phases.
Area of Science:
- Microbiology
- Pharmacology
- Genetics
Background:
- Enterococci possess inherent resistance to many antibiotics.
- Acquired genetic traits contribute to increasing enterococcal drug resistance.
- Penicillin resistance in enterococci is linked to low-affinity penicillin-binding proteins (PBP) and potential autolytic system deficiencies.
Purpose of the Study:
- To investigate the bactericidal activity of beta-lactam antibiotics against enterococci.
- To characterize the "paradoxical effect" and "tolerance" phenomena in enterococcal antibiotic resistance.
- To explore the influence of bacterial growth phase and genetic mutations on beta-lactam-induced autolysis.
Main Methods:
- Evaluation of beta-lactam bactericidal activity.
- Analysis of "paradoxical effect" in different culture phases (exponential vs. aged).
- Assessment of beta-lactam-induced autolysis in wild-type and mutated enterococcal strains.
Main Results:
- The "paradoxical effect" was more pronounced in exponential phase cultures compared to aged cultures.
- Mutated enterococcal strains exhibited a genetically determined increase in the "paradoxical effect".
- Different beta-lactams induced varying degrees of bacterial autolysis.
Conclusions:
- The "paradoxical effect" in enterococci is influenced by growth phase and genetic factors.
- Bacterial autolysis is differentially modulated by various beta-lactams.
- Understanding these resistance mechanisms is crucial for effective enterococcal infection treatment.