Klebsiella pneumoniae carbapenemase
Klebsiella pneumoniae carbapenemase (KPC) is a group of enzymes that break down carbapenem antibiotics. As more than one enzyme, that can do this, can be found in Klebsiella, when not specified, KPC usually refers to KPC-1 coded by the bla gene (which was not the first to be described, but KPC-2 encoded by the same gene has been shown to be identical). Another enzyme that breaks down some carbapenems is beta-lactamase NDM-1.
This is of particular significance because KPC-1 occurs within a particular type of transposon which increased its ability to cross species into other Gram-negative organisms. They are also typically found in association with other forms of antibiotic resistance. Clinically, it presents a problem because carbapenems have typically been the antibiotic class of choice for Gram-negative organisms with extended-spectrum beta-lactamases (ESBL). In the presence of KPC, the choice of antibiotics is limited.
The antibiotics used with the laboratory for in vitro testing of antibiotic susceptibility are slightly different from those in clinical setting. In the presence of KPC, these tend to give a false impression of susceptibility.