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Postantibiotic effect, and postantibiotic effect of subinhibitory concentrations, of sparfloxacin on gram-negative
I Odenholt-Tornqvist1, S Bengtsson
1Department of Infectious Diseases, University Hospital, Uppsala, Sweden.
Abstract:
The postantibiotic effect (PAE), the postantibiotic sub-MIC effect (PA SME), and the sub-MIC effect (SME) of a new oral quinolone, sparfloxacin, were determined for different strains of gram-negative bacteria. A PAE was induced by 10 x MIC of sparfloxacin for 2 h and the antibiotic was then eliminated by washing and dilution. The PA SME was studied by adding different sub-MICs during the postantibiotic phase, and the SME by exposing the controls to the sub-MICs alone. Growth curves were followed for 20 h by continuous monitoring of optical density in an automatic incubator. Sparfloxacin induced a PAE of 0.9-2.4 h for all strains except two clinical strains of Enterobacter cloacae. In accordance with earlier experiments with sparfloxacin and gram-positive bacteria, this study showed a PA SME that was nearly equal to the PAE plus the effect of the subinhibitory concentration alone (SME).
Insights
Sparfloxacin demonstrated a significant postantibiotic effect (PAE) against most gram-negative bacteria. The study also observed a postantibiotic sub-MIC effect (PA SME) comparable to the sum of PAE and sub-MIC effect (SME).
Area of Science:
- Microbiology
- Pharmacology
- Bacteriology
Background:
- The emergence of antibiotic resistance necessitates the development of new antimicrobial agents.
- Understanding the pharmacokinetic and pharmacodynamic properties of antibiotics is crucial for optimizing their efficacy.
- Sparfloxacin is a novel oral quinolone with broad-spectrum activity.
Purpose of the Study:
- To determine the postantibiotic effect (PAE), postantibiotic sub-MIC effect (PA SME), and sub-MIC effect (SME) of sparfloxacin.
- To evaluate these effects on various gram-negative bacterial strains.
- To compare the observed effects with previously reported data.
Main Methods:
- Bacterial strains were exposed to sparfloxacin at 10x MIC for 2 hours to induce PAE.
- Sub-inhibitory concentrations (sub-MICs) were applied during the postantibiotic phase to assess PA SME.
- Control groups were exposed to sub-MICs alone to determine SME.
- Bacterial growth was monitored for 20 hours using optical density measurements.
Main Results:
- Sparfloxacin induced a PAE ranging from 0.9 to 2.4 hours in most tested gram-negative strains.
- Two clinical strains of Enterobacter cloacae exhibited no significant PAE.
- The PA SME was found to be approximately equal to the sum of PAE and SME, consistent with prior sparfloxacin studies.
Conclusions:
- Sparfloxacin exhibits a notable PAE against a broad range of gram-negative bacteria.
- The PA SME phenomenon, where sub-inhibitory concentrations extend the antibiotic effect, is confirmed for sparfloxacin.
- These findings contribute to understanding sparfloxacin's antibacterial mechanisms and potential clinical applications.