Open Access Highly Accessed Research article

Comparative in vitro activity of Meropenem, Imipenem and Piperacillin/tazobactam against 1071 clinical isolates using 2 different methods: a French multicentre study

Marie-Laure Joly-Guillou1*, Marie Kempf1, Jean-Didier Cavallo2, Monique Chomarat3, Luc Dubreuil4, Jeanne Maugein5, Claudette Muller-Serieys6 and Micheline Roussel-Delvallez7

Author Affiliations

1 Bacteriology department, Universitary Hospital, (Larrey St), Angers (49000), France

2 Bacteriology department, Begin Military Hospital, (Paris Ave), St Mandé, (94163), France

3 Bacteriology department, Universitary Hospital Lyon-Sud, Pierre Bénite, (69310), France

4 Faculty of Pharmacy, (Dr Laguesse St), Lille, (59006), France

5 Bacteriology department, Haut Leveque Hospital, (Magellan Ave), Pessac, (33604), France

6 Bacteriology department, Universitary Hospital Bichat Claude Bernard, AP-HP, Paris, (75018), France

7 Bacteriology department, Universitary Hospital Calmette, (J. Leclercq Bd), (59037), Lille, France

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BMC Infectious Diseases 2010, 10:72  doi:10.1186/1471-2334-10-72

Published: 18 March 2010



Meropenem 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.


Susceptibility 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.


Cumulative 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.


Compared 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.