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Postantibiotic effect of imipenem on gram-positive and gram-negative micro-organisms
Abstract:
The bactericidal effect (BE) of an antibiotic reduces the infective population, and its postantibiotic effect (PAE) assures a persistent inhibition of bacterial cells after a short exposure to the antimicrobial agent. Both effects prevent the early regrowth of the infecting organisms when the antibiotic tissue levels decrease to below the MIC value. The BE and the PAE of imipenem, cefotaxime, ceftazidime, piperacillin, gentamicin and ampicillin on Escherichia coli, Klebsiella pneumoniae, Enterobacter cloacae, Pseudomonas aeruginosa, Acinetobacter calcoaceticus, Staphylococcus aureus and Streptococcus faecalis were investigated with viable counts and continuous impedance monitoring of broth cultures. Imipenem and gentamicin gave similar high BE and PAE values at low concentrations and with short drug exposures in most strains tested. PAE is low or non-existent for Gram-negative strains with other beta-lactam antibiotics. These results suggest the possibility of future clinical studies with new experimental dosage schedules for imipenem.
Insights
Imipenem and gentamicin show strong bactericidal (BE) and postantibiotic (PAE) effects against various bacteria, even at low doses. Other beta-lactam antibiotics have limited PAE on Gram-negative bacteria.
Area of Science:
- Microbiology
- Pharmacology
- Infectious Diseases
Background:
- Antibiotic bactericidal effect (BE) reduces bacterial populations.
- Postantibiotic effect (PAE) inhibits bacterial growth after antibiotic exposure.
- BE and PAE prevent pathogen regrowth when antibiotic levels drop below MIC.
Purpose of the Study:
- To investigate the BE and PAE of specific antibiotics on various bacterial strains.
- To compare the efficacy of imipenem, cefotaxime, ceftazidime, piperacillin, gentamicin, and ampicillin.
- To evaluate antibiotic performance against Gram-positive and Gram-negative bacteria.
Main Methods:
- Utilized viable counts and continuous impedance monitoring.
- Assessed BE and PAE of antibiotics including imipenem and gentamicin.
- Tested against a panel of bacteria: E. coli, K. pneumoniae, E. cloacae, P. aeruginosa, A. calcoaceticus, S. aureus, S. faecalis.
Main Results:
- Imipenem and gentamicin demonstrated high BE and PAE values across most tested strains.
- These effects were observed at low antibiotic concentrations and short exposure times.
- Other beta-lactam antibiotics exhibited minimal or no PAE on Gram-negative bacteria.
Conclusions:
- Imipenem and gentamicin are effective in reducing bacterial load and inhibiting regrowth.
- The findings support further clinical research into novel dosing strategies for imipenem.
- Beta-lactam antibiotics may be less effective for postantibiotic effect against Gram-negative pathogens.