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[Comparative bactericidal activity of imipenem and other antibiotics against Pseudomonas aeruginosa]
Abstract:
The bactericidal activity of imipenem (IM), ticarcillin (TIC), ceftazidime (CEZ), amikacin (AMK) or tobramycin (TOB), ciprofloxacin (CIP), was compared on 6 P. aeruginosa: 1 ticarcillin, susceptible strain (TICs), 5 constitutive beta-lactamases producing strains (PSE, TEM, OXA1, OXA2, cephalosporinase (CEP). The time-kill-curves method was performed. Bacteria were incubated with antibiotics at M.I.C. X2 and at concentrations obtained in vivo with usual therapeutic doses: IM 4-8 mg/l, TIC 64-128, CEZ 4-32, TOB 2-8, AMK 4-16, CIP 1-4. The bactericidal activity of IM was independent of the concentration. A 5 Log10 reduction in viability was observed at 3 h for strains TICs, TEM and PSE, 3 Log10 for strains OXA and CEP. This bactericidal activity was also observed in a non growing system. The bactericidal activity of TIC (strain TICs) and CEZ was slower and weaker: 1-2 Log10 at 6 h, 2-3 Log10 at 24 h. It is not observed in a non growing system. On the other hand, the bactericidal activity of aminoglycosides and ciprofloxacin was rapid: 3-4 Log10 at 3 h, 5 Log10 at 6 h for all strains in growing and non growing systems. IM is the only beta-lactam antibiotic bactericidal on growing and non growing cells of P. aeruginosa like aminoglycosides and new quinolones.
Insights
Imipenem demonstrated potent bactericidal activity against Pseudomonas aeruginosa, including non-growing cells, unlike other beta-lactams. Aminoglycosides and ciprofloxacin also showed rapid killing of P. aeruginosa.
Area of Science:
- Microbiology
- Pharmacology
- Infectious Diseases
Background:
- Pseudomonas aeruginosa is an opportunistic pathogen.
- Antibiotic resistance in P. aeruginosa is a growing concern.
- Understanding bactericidal activity is crucial for effective treatment.
Purpose of the Study:
- To compare the bactericidal activity of various antibiotics against P. aeruginosa.
- To evaluate antibiotic efficacy against beta-lactamase producing strains.
- To assess antibiotic activity in growing and non-growing bacterial systems.
Main Methods:
- Time-kill-curve assays were performed.
- Antibiotics tested included imipenem, ticarcillin, ceftazidime, amikacin, tobramycin, and ciprofloxacin.
- Bacteria were incubated at concentrations simulating therapeutic doses.
Main Results:
- Imipenem exhibited concentration-independent bactericidal activity against most P. aeruginosa strains, including non-growing cells.
- Ticarcillin and ceftazidime showed slower and weaker bactericidal effects, not observed in non-growing cells.
- Aminoglycosides (amikacin, tobramycin) and ciprofloxacin demonstrated rapid bactericidal activity against all tested strains, in both growing and non-growing states.
Conclusions:
- Imipenem possesses unique bactericidal properties against P. aeruginosa, similar to aminoglycosides and fluoroquinolones.
- Beta-lactamase production significantly impacts the efficacy of some beta-lactam antibiotics.
- Effective treatment strategies for P. aeruginosa infections may involve antibiotics with broad-spectrum bactericidal activity.