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Use of Etests with carbapenems for Gram-negative rods producing beta-lactamases
Bekir S Kocazeybek1, Umit Arabaci
1Cerrahpaşa Medical Faculty, Microbiology and Clinical Microbiology Department, University of Istanbul, Cerrahpaşa, Istanbul, Turkey. bekirkcz@superonline.com
Abstract:
The in vitro activity of imipenem and meropenem on strains of Gram-negative rods producing extended-spectrum beta-lactamase (ESBL) and inducible beta-lactamase (IBL) was studied using the Etest. In all, 185 strains from the surgical intensive care units of four different hospitals were looked at over 2 years. Of these, 94 were ESBL producers and 91 were IBL positive. The in vitro sensitivities of imipenem and meropenem were 89.7 and 95.1%, respectively, against all strains. The imipenem and meropenem sensitivities of Klebsiella spp. were 98.4 and 100%, respectively, but imipenem resistance (21.6%) in Pseudomonas aeruginosa strains was higher than that of meropenem (10.8%).
Insights
Meropenem showed higher in vitro activity against Gram-negative rods producing extended-spectrum beta-lactamase (ESBL) and inducible beta-lactamase (IBL) compared to imipenem. Meropenem demonstrated superior sensitivity, particularly in Pseudomonas aeruginosa strains.
Area of Science:
- Clinical Microbiology
- Infectious Diseases
- Pharmacology
Background:
- Carbapenem antibiotics are crucial for treating infections caused by Gram-negative bacteria producing extended-spectrum beta-lactamases (ESBLs) and inducible beta-lactamases (IBLs).
- Emergence of resistance to carbapenems necessitates ongoing surveillance of antibiotic activity against these challenging pathogens.
Purpose of the Study:
- To evaluate and compare the in vitro activity of imipenem and meropenem against Gram-negative bacterial strains.
- To assess the prevalence of ESBL and IBL production in strains isolated from surgical intensive care units.
Main Methods:
- The Etest method was employed to determine the in vitro susceptibility of 185 Gram-negative bacterial isolates.
- Isolates were collected from surgical intensive care units across four hospitals over a two-year period.
- Bacterial strains were characterized for the production of extended-spectrum beta-lactamase (ESBL) and inducible beta-lactamase (IBL).
Main Results:
- Overall in vitro sensitivities were 89.7% for imipenem and 95.1% for meropenem against all tested strains.
- Klebsiella spp. exhibited high sensitivities to both agents (98.4% for imipenem, 100% for meropenem).
- Pseudomonas aeruginosa showed higher imipenem resistance (21.6%) compared to meropenem resistance (10.8%).
Conclusions:
- Meropenem demonstrates superior in vitro activity compared to imipenem against a broad range of Gram-negative rods, including ESBL and IBL producers.
- Meropenem may be a more reliable therapeutic option for infections caused by these resistant Gram-negative bacteria, especially Pseudomonas aeruginosa.