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Comparison of two commercial methods for determination of the minimum inhibitory meropenem concentration in kpc carbapenemase-producing klebsiella pneumoniae

Abstract:

Introduction: The treatment for KPC carbapenemase-producing Klebsiella pneumoniae infections is complicated, due to the scant therapeutic options available, which forces us to optimize the therapies at hand. Objective: Determine the agreement between the AST-N272 card of the Vitek 2 Compact system and the M.I.C.E.™ Evaluator strips, and the agar dilution method for determination of the minimum inhibitory meropenem concentration in KPC carbapenemase-producing Klebsiella pneumoniae. Methods: A study was conducted of 53 positive non-clonal K. pneumoniae blaKPC isolates from rectal swabs collected at several hospitals in Guayaquil, Ecuador, from January to June 2016. Minimum inhibitory meropenem concentration was determined by agar dilution (reference method), the Vitek 2 Compact system (AST-N272) and M.I.C.E.™ strips. Determination was made of MIC 50, MIC 90 and essential agreement. Results: The meropenem MIC range for the isolates studied was 1 to ≥ 32 µg/ml, with MIC50= 4 µg/ml and MIC90= ≥ 32 µg/ml. In 86.79% (n= 46) of the isolates MIC was ≤ 8 µg/ml. Essential agreement was 94.33% with the M.I.C.E.™ strips and under 50% with the AST-N272 card. Conclusions: The results obtained suggest potential implications for the treatment of patients, since therapeutic options are reduced in difficult management contexts. They also highlight the need for confirmation of carbapenem resistance by the Kirby-Bauer procedure in laboratories equipped with automated methods for susceptibility studies.