A Comparative in Vitro Microbiological Evaluation of Generic Meropenem Compounds against the Innovator Compound

ABSTRACT

Background: Meropenem is a broad-spectrum carbapenem widely used in the treatment of critically ill patients. A generic meropenem product has recently become available in South Africa and we aimed to compare the generic product with the innovator product using established in vitro microbiological testing methods.Method: Comparative minimum inhibitory concentrations (MICs) were determined for 115 clinically relevant isolates using the broth microdilution reference method. Comparative analysis of MIC was done using categorical and essential agreement. A subset of isolates was evaluated using minimum bactericidal concentration (MBC) testing. Results: The overall essential agreement exceeded the international standard of 90. A single major error and six minor errors were detected in 230 comparative MICs. For the 55 Enterobacteriaceae isolates tested; the MIC50 and MIC90 were 0.03 ?g/ml and 0.06 ?g/ml respectively; with no difference between extended-spectrum Beta-lactamase producers (ESBL) and non-ESBL isolates. Bactericidal activity was demonstrated for both generic and innovator products in all isolates tested. For eight of the 11 isolates; the MBC was only twice the MIC.Conclusion: Reference method MIC and MBC testing of a large sample of clinically relevant microorganisms against meropenem has demonstrated comparable in vitro activity between the innovator and generic products. Low MICs and bactericidal activity at concentrations close to the MIC indicate that meropenem remains a useful agent in the treatment of infections caused by ESBL-producing Enterobacteriaceae