Carbapenem resistance caused by high-level expression of OXA-663 -lactamase in an OmpK36-deficient klebsiella pneumoniae clinical isolate

Abstract

Carbapenem resistance is mainly mediated by carbapenemases or extended-spectrum -lactamases (ESBL) plus a loss of porins. However, we have identified a Klebsiella pneumoniae clinical isolate that contains neither carbapenemases nor ESBLs. Instead, we found that high-level expression of a novel blaOXA-10-derived -lactamase gene, blaOXA-663, in conjunction with OmpK36 deficiency results in high-level carbapenem resistance. This finding demonstrates the combinatorial complexity of factors, including -lactamase activity, its expression levels, and porin activity, that yield carbapenem resistance.