Epidemiology and resistance mechanisms to imipenem in Klebsiella pneumoniae: a multicenter study.

Four clinical isolates of imipenem-resistant Klebsiella pneumoniae were isolated from clinical patient specimens and from samples obtained from hygienic surveillance in our hospital. We examined their minimum inhibitory concentration (MIC) to various types of antibiotics, detected the carbapenemases by a modified Hodge test and analyzed the genotype and homogeneity. The enzyme, Klebsiella pneumoniae carbapenemase (KPC)-2, was detected in all four isolates and this was the main cause of their imipenem resistance. In addition, these four isolates also contained the extended-spectrum β-lactamase (ESBL) gene blaCTX-M-9 and the cephalosporinase (AmpC) gene blaDHA-1, which resulted in multidrug resistance.