COMPARISON OF IN VITRO ACTIVITIES OF DORIPENEM AND OTHER CARBAPENEMS AGAINST CLINICAL ISOLATES OF EXTENDED SPECTRUM BETA-LACTAMASE-PRODUCING GRAM NEGATIVE BACILLI

Abstract

Introduction: Doripenem has been recognized as a valuable addition to the currently available carbapenems. Objectives: The purpose of this study was to compare the in vitro activity of doripenem with other carbapenems (meropenem and imipenem) against clinical isolates of ESBL-producing Gram negative bacilli. Material and Methods: A total of 355 Gram-negative bacilli were isolated from specimens obtained from outpatient clinic attendants and inpatients submitted to the Microbiology Laboratory of Theodor Bilharz Research Institute, during the period from October 2011 to May 2012. ESBL screening and confirmation among isolates were performed according to the Clinical and Laboratory Standards Institute criteria. Minimal inhibitory concentrations of doripenem, imipenem and meropenem were determined for ESBL producing isolates by the E-test. Results: Out of 355 Gram negative bacilli, 14.1% were ESBL producers mainly K.pneumoniae and E.coli. All E.coli ESBL isolates were sensitive to doripenem, 97.1% were sensitive to meropenem and 88.6%were sensitive to imipenem. The MIC50 was 0.023, 0.047 and 0.25, respectively for doripenem, meropenem, and imipenem, while the MIC90 was 0.094, 0.064 and 1.5, respectively for doripenem, meropenem and imipenem. Meanwhile, all K.pneumoniae ESBL isolates were sensitive to doripenem, 93.3% were sensitive to meropenem and 93.3% were sensitive to imipenem. The MIC50 was 0.047, 0.047 and 0.25, respectively for doripenem, meropenem and imipenem, while the MIC90 was 0.094, 0.5 and 1.0, respectively for doripenem, meropenem and imipenem. Conclusion: On basis of the in vitro data, doripenem was nearly similar to meropenem but was superior to imipenem against ESBL-producing Enterobacteriaceae. Doripenem appears to be a promising agent for the treatment of ESBL infections.