Related Experiment Videos
Paradoxical effects of antibiotics
S E Holm1, I O Tornqvist, O Cars
1Department of Clinical Bacteriology, Umeå University Hospital, Sweden.
Scandinavian Journal of Infectious Diseases. Supplementum
|January 1, 1990
Summary
Antibiotics can be less effective at high doses, a paradoxical effect observed in vitro. This phenomenon, seen with various antibiotic classes and bacteria, occurs at clinically relevant concentrations.
Area of Science:
- Microbiology
- Pharmacology
- Infectious Diseases
Background:
- The paradoxical effect of antibiotics is defined as reduced bacterial killing at concentrations above the minimal bactericidal concentration (MBC).
- Initially observed with beta-lactam antibiotics against Gram-positive bacteria, it has since been documented for other antibiotic-microorganism combinations, suggesting diverse mechanisms.
- The clinical relevance of this phenomenon remains largely unknown.
Purpose of the Study:
- To investigate the paradoxical effect of antibiotics in vitro.
- To determine the occurrence and concentration-dependent nature of the paradoxical effect using clinical isolates of Staphylococcus aureus and various penicillins.
Main Methods:
- In vitro testing of clinical isolates of Staphylococcus aureus against several penicillins.
- Determination of bacterial killing at varying antibiotic concentrations, including levels above the minimal bactericidal concentration (MBC).
Main Results:
- The paradoxical effect was observed in a significant proportion of Staphylococcus aureus strains tested.
- This effect frequently occurred at antibiotic concentrations as low as 10 times the minimal inhibitory concentration (MIC).
- The study demonstrates that the paradoxical effect can manifest at clinically achievable antibiotic levels.
Conclusions:
- The paradoxical effect of antibiotics is a reproducible in vitro phenomenon.
- It can occur at clinically relevant concentrations, highlighting potential implications for antibiotic therapy.
- Further research is needed to elucidate the clinical significance and underlying mechanisms of the paradoxical effect and its relationship with bacterial tolerance.