Abstract
BackgroundMeropenem is a carbapenem that has an excellent activity against many gram-positive and gram-negative aerobic, facultative, and anaerobic bacteria. The major objective of the present study was to assess the in vitro activity of meropenem compared to imipenem and piperacillin/tazobactam, against 1071 non-repetitive isolates collected from patients with bacteremia (55%), pneumonia (29%), peritonitis (12%) and wound infections (3%), in 15 French hospitals in 2006. The secondary aim of the study was to compare the results of routinely testings and those obtained by a referent laboratory.MethodSusceptibility testing and Minimum Inhibitory Concentrations (MICs) of meropenem, imipenem and piperacillin/tazobactam were determined locally by Etest method. Susceptibility to meropenem was confirmed at a central laboratory by disc diffusion method and MICs determined by agar dilution method for meropenem, imipenem and piperacillin/tazobactam.ResultsCumulative susceptibility rates against Escherichia coli were, meropenem and imipenem: 100% and piperacillin/tazobactam: 90%. Against other Enterobacteriaceae, the rates were meropenem: 99%, imipenem: 98% and piperacillin/tazobactam: 90%. All Staphylococci, Streptococci and anaerobes were susceptible to the three antibiotics. Against non fermeters, meropenem was active on 84-94% of the strains, imipenem on 84-98% of the strains and piperacillin/tazobactam on 90-100% of the strains.ConclusionsCompared to imipenem, meropenem displays lower MICs against Enterobacteriaceae, Escherichia coli and Pseudomonas aeruginosa. Except for non fermenters, MICs90 of carbapenems were <4 mg/L. Piperacillin/tazobactam was less active against Enterobacteriaceae and Acinetobacter but not P. aeruginosa. Some discrepancies were noted between MICs determined by Etest accross centres and MICs determined by agar dilution method at the central laboratory. Discrepancies were more common for imipenem testing and more frequently related to a few centres. Overall MICs determined by Etest were in general higher (0.5 log to 1 log fold) than MICs by agar dilution.
Highlights
Meropenem is a carbapenem that has an excellent activity against many gram-positive and gramnegative aerobic, facultative, and anaerobic bacteria
Piperacillin/tazobactam was less active against Enterobacteriaceae and Acinetobacter but not P. aeruginosa
Some discrepancies were noted between Minimum Inhibitory Concentrations (MICs) determined by Etest accross centres and MICs determined by agar dilution method at the central laboratory
Summary
Meropenem is a carbapenem that has an excellent activity against many gram-positive and gramnegative aerobic, facultative, and anaerobic bacteria. The major objective of the present study was to assess the in vitro activity of meropenem compared to imipenem and piperacillin/tazobactam, against 1071 non-repetitive isolates collected from patients with bacteremia (55%), pneumonia (29%), peritonitis (12%) and wound infections (3%), in 15 French hospitals in 2006. One of the most cited global surveillance studies includes the Meropenem Yearly Susceptibility Test Information Collection (MYSTIC) program, an international resistance surveillance study which has been initiated 10 years ago with more than 100 participants worldwide [2,3,4,5,6,7,8,9]. The major objective of the present study was to assess the in vitro activity of meropenem which has been recently re-introduced in French hospitals, compared to imipenem and piperacillin/tazobactam, against clinical isolates included in the spectrum of meropenem. The secondary aim of the study was to compare the results of routinely testings and those obtained by a central laboratory
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