Impact of porin deletions on cefepime-taniborbactam activity against <i>Klebsiella pneumoniae</i>

We determined the frequency of resistance to cefepime-taniborbactam in NDM-1-producing <i>Klebsiella pneumoniae</i> at <10^-10. Isolated mutants that were less susceptible to cefepime-taniborbactam had an increased copy number of the <i>bla</i>_NDM-1 gene or disruption of major porins OmpK36 and OmpK35. Antibacterial susceptibility testing using <i>K. pneumoniae</i> isogenic strains indicated that while cefepime penetrates into the periplasm mainly through the major porins, taniborbactam does not have a strong dependence on OmpK35 or OmpK36 for periplasmic accumulation.