KPC-12 with a L169M substitution in the Ω loop has reduced carbapenemase activity.

KPC-12 is a variant of KPC-2 with a L169M substitution in the Ω loop, but its resistance spectrum was not reported. blaKPC-12 was cloned, and KPC-12 exhibited significantly decreased activities against imipenem, meropenem, aztreonam, and piperacillin-tazobactam with ≥4-fold lower MICs than KPC-2. However, unlike the L169P substitution in KPC-35, activities against ceftazidime and ceftazidime-avibactam of KPC-12 were unaltered. This highlights that different substitutions at the same position of carbapenemases may have varied impact on the activity.