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Postantibiotic sub-MIC effects of vancomycin, roxithromycin, sparfloxacin, and amikacin
I Odenholt-Tornqvist1, E Löwdin, O Cars
1Department of Infectious Diseases, Uppsala University, Sweden.
Abstract:
The sub-MIC effects (SMEs) and the postantibiotic sub-MIC effects (PA SMEs) of vancomycin, roxithromycin, and sparfloxacin for Streptococcus pyogenes and Streptococcus pneumoniae and of amikacin for Escherichia coli and Pseudomonas aeruginosa were investigated. A postantibiotic effect was induced by exposing strains to 10x the MIC of the antibiotic for 2 h in vitro. After the induction, the exposed cultures were washed to eliminate the antibiotics. Unexposed controls were treated similarly. Thereafter, the exposed cultures (PA SME) and the controls (SME) were exposed to different subinhibitory concentrations (0.1, 0.2, and 0.3x the MIC) of the same drug and growth curves for a period of 24 h were compared. In general, the PA SMEs were much more pronounced than the SMEs. However, for amikacin and E. coli the SME of 0.2 and 0.3x the MIC also had an initial bactericidal effect. The longest PA SMEs were demonstrated for the combinations with the most pronounced killing during the induction and for the combinations which exhibited the longest PAEs.
Insights
This study investigated antibiotic sub-inhibitory effects (SMEs) and postantibiotic sub-inhibitory effects (PA SMEs) on bacteria. Postantibiotic effects were generally more pronounced than sub-inhibitory effects.
Area of Science:
- Microbiology
- Pharmacology
- Antimicrobial Resistance
Background:
- Sub-inhibitory concentrations (sub-MICs) of antibiotics can influence bacterial growth and behavior.
- Understanding postantibiotic effects is crucial for optimizing antibiotic therapy and combating resistance.
Purpose of the Study:
- To investigate the sub-MIC effects (SMEs) and postantibiotic sub-MIC effects (PA SMEs) of various antibiotics on specific bacterial strains.
- To compare the magnitude and duration of SMEs and PA SMEs.
Main Methods:
- Bacterial strains (Streptococcus pyogenes, Streptococcus pneumoniae, Escherichia coli, Pseudomonas aeruginosa) were exposed to antibiotics (vancomycin, roxithromycin, sparfloxacin, amikacin) at 10x MIC for 2 hours.
- Following antibiotic removal, cultures were exposed to different sub-MICs (0.1, 0.2, 0.3x MIC) for 24 hours.
- Growth curves were compared between antibiotic-exposed and control groups.
Main Results:
- Postantibiotic sub-MIC effects (PA SMEs) were generally more pronounced than sub-MIC effects (SMEs).
- Amikacin exhibited an initial bactericidal effect on Escherichia coli at 0.2 and 0.3x MIC.
- The longest PA SMEs were observed with antibiotic combinations showing significant killing during induction and prolonged postantibiotic effects (PAEs).
Conclusions:
- Antibiotic exposure, even at sub-inhibitory concentrations, can have lasting effects on bacterial growth.
- PA SMEs are a significant phenomenon that warrants further investigation in clinical settings.
- The interplay between antibiotic concentration, duration of exposure, and bacterial response influences the observed effects.