Methicillin-resistant Staphylococcus aureus (MRSA) has grabbed recent national media attention and alarmed the public, but there has been little publicized about the emergence of resistance among enteric Gram negative bacilli. There is a resistance mechanism called KPC, Klebsiella pneumoniae carbapenamase, that has been described within the past decade. KPCs are carbapenemases that reside on transferable plasmids and can hydrolyze all penicillins, cephalosporins, and carbapenems.
Carbapenems, such as imipenem, ertapenem, and meropenem, are often used to treat infections caused by multidrug-resistant pathogens, including extended-spectrum beta-lactamase (ESBL) producing Gram negative bacilli. In addition to resistance to the beta-lactam drugs and carbapenems, KPC-producing organisms are often resistant to fluoroquinolones and aminoglycosides, leaving very few options for treatment of serious infection.
In 1996, the first isolate of KPC-producing bacteria was discovered in a clinical specimen of Klebsiella pneumoniae from a hospital in North Carolina. KPCs were infrequently isolated until 2001, when KPC-producing organisms were reported in several extended outbreaks in metropolitan hospitals of New York and New Jersey. KPC-producing organisms have continued to spread over time and have now been reported in 27 states of the United States and in many countries around the world. There have been no reports of KPC organisms isolated in Northern California thus far, although there have been a few cases in Southern California.
Although most KPCs are detected in isolates of Klebsiella and E.coli, KPCs have been extensively reported in other genera of enteric bacilli such as Proteus, Serratia, Salmonella and Citrobacter. In addition, KPC resistance has been reported in multidrug-resistant Pseudomonas aeruginosa.
The global spread of KPC-producing organisms appears to have been rapid, perhaps because KPC infection and colonization were previously unrecognized, or because several factors related to in vitro susceptibility testing can complicate their detection. Difficulties in detection may result in an underestimation of the true incidence of KPC producing organisms.
The Microbiology Department at MuirLab screens all Gram negative enteric bacilli and Pseudomonas for the presence of KPC, and has the capability of performing phenotypic confirmation of KPC. Those isolates that may be KPC-producers will be sent to the Public Health Department for molecular analysis.
Carbapenems have long been a reliable last line of defense in the treatment of infections caused by resistant enteric Gram negative organisms. Increased awareness & intensified infection control practices are the keys to curtail the spread of KPC antimicrobial resistance.