In vivo development of ertapenem resistance in a patient with pneumonia caused by Klebsiella pneumoniae with an extended-spectrum beta-lactamase

Abstract

Four sequential extended-spectrum beta -lactamase-producing isolates of Klebsiella pneumoniae were obtained from a patient after treatment with ertapenem and cultured. The first and fourth isolates were susceptible to ertapenem, whereas the second and third were resistant. All 4 isolates belonged to the same strain and produced a group 1 CTX-M enzyme; additionally, the resistant isolates had lost a porin.