Carbapenem resistance caused by high-level expression of OXA-663 {beta}-lactamase in an OmpK36-deficient Klebsiella pneumoniae clinical isolate [PublishAheadOfPrint]

Carbapenem resistance is mainly mediated by carbapenemases or extended-spectrum β-lactamases (ESBL) plus 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 bla_OXA-10-derived β-lactamase gene, bla_OXA-663, in conjunction with OmpK36 deficiency results in high-level carbapenem resistance. This finding demonstrates the combinatorial complexity of factors including β-lactamase activity, its expression levels, and porin activity that yield carbapenem resistance.

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