KPC

KPC
Name	KPC
Classification	Carbapenemase; serine β-lactamase
First described	2001
Gene	blaKPC
Hosts	Enterobacterales, Klebsiella pneumoniae, Escherichia coli
Transmission	Plasmid-mediated horizontal gene transfer

KPC

KPC is a class of plasmid-encoded serine carbapenemase first identified in Klebsiella pneumoniae isolates and subsequently found across diverse Enterobacterales and non-fermenters. It has been implicated in nosocomial outbreaks associated with high morbidity and mortality in settings including intensive care unit, long-term care facility, and transplantation programs. International spread has linked KPC-producing strains to intercontinental patient transfer, referral networks, and clonal lineages such as sequence type 258 that have been reported in United States, Italy, Israel, Colombia, China, and Greece.

Overview

KPC enzymes are members of the Ambler class A β-lactamases and confer resistance to carbapenems such as imipenem, meropenem, and ertapenem, as well as penicillins and cephalosporins, compromising therapies used for severe infections like sepsis and bacteremia. The blaKPC gene is frequently carried on conjugative plasmids mobilized by insertion sequences and transposons including Tn4401, facilitating spread between clinical species such as Klebsiella aerogenes, Enterobacter cloacae, Serratia marcescens, and Pseudomonas aeruginosa. Public health responses have involved coordination among agencies like the Centers for Disease Control and Prevention and European Centre for Disease Prevention and Control.

Microbiology and Genetics

KPC enzymes hydrolyze β-lactam rings via a serine residue at the active site, distinguishing them from metallo-β-lactamases such as NDM-1 and VIM. Multiple KPC variants (e.g., KPC-2, KPC-3) arise through point mutations in blaKPC, which resides within mobile elements like Tn4401 embedded in plasmid backbones (IncF, IncN, IncL/M). Clonal expansion of lineages such as ST258 in Klebsiella pneumoniae has been augmented by plasmid fitness determinants and co-carried resistance genes including blaCTX-M, blaSHV, and aminoglycoside-modifying enzymes, as seen in reports linking KPC to global high-risk clones documented by networks including PulseNet and ECDC surveillance.

Clinical Significance and Epidemiology

KPC-producing organisms cause urinary tract infections, ventilator-associated pneumonia, intra-abdominal infections, and catheter-related bloodstream infections in patients receiving care in acute care hospital, long-term acute care hospital, hematology-oncology unit, and neonatal intensive care unit environments. Outbreak investigations have implicated healthcare-associated transmission via contaminated hands, devices, sinks, and environmental reservoirs, prompting studies published in journals associated with Infectious Diseases Society of America and surveillance data from WHO networks. Mortality rates for invasive KPC infections have been elevated in cohorts treated before availability of newer agents, with risk factors including prior carbapenem exposure, prolonged hospitalization, and invasive procedures such as central venous catheterization.

Mechanism of Resistance

The KPC enzyme catalyzes hydrolysis of the β-lactam amide bond through formation of an acyl-enzyme intermediate involving the active-site serine (S70). Structural studies comparing KPC variants to TEM-1 and SHV-1 reveal conformational features permitting carbapenem accommodation and deacylation, reducing efficacy of carbapenems. Resistance is compounded by porin alterations (e.g., mutations in OmpK35 and OmpK36) and upregulation of efflux pumps such as AcrAB-TolC, leading to elevated minimum inhibitory concentrations and treatment failure with β-lactam/β-lactamase inhibitor combinations absent specific inhibitor activity against class A carbapenemases.

Diagnosis and Laboratory Detection

Laboratory identification employs phenotypic assays (modified Hodge test, carbapenem inactivation method, Carba NP) and automated susceptibility platforms like VITEK 2 and MicroScan for initial screening, followed by confirmatory molecular methods targeting blaKPC via PCR and sequencing. Whole-genome sequencing used by reference laboratories and initiatives such as GenomeTrakr enables detection of plasmid types, insertion sequences, and clonal relationships. Lateral flow immunochromatographic assays and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF) hydrolysis tests provide rapid diagnostics in clinical microbiology workflows.

Treatment and Management

Therapeutic options have evolved from combination regimens (polymyxins such as colistin, tigecycline, aminoglycosides) toward targeted agents including novel β-lactam/β-lactamase inhibitor combinations with activity against class A carbapenemases such as ceftazidime/avibactam and meropenem/vaborbactam, as well as agents like plazomicin and cefiderocol under specific susceptibility guidance. Antimicrobial stewardship programs and infectious diseases consultation by specialists from organizations such as IDSA guide individualized therapy based on pharmacokinetics/pharmacodynamics, site of infection, and susceptibility data. Adjunctive measures involve source control procedures and removal of infected devices in coordination with surgical and interventional teams.

Prevention and Control

Containment relies on infection prevention measures including hand hygiene standards endorsed by WHO and contact precautions in healthcare settings, active surveillance cultures, cohorting of colonized patients, environmental cleaning protocols, and antimicrobial stewardship interventions promoted by CDC initiatives. Outbreak control has used molecular epidemiology to trace transmission routes, interfacility communication during patient transfers, and policies for screening high-risk populations such as recent travelers to regions with endemic carbapenemases. Public health strategies integrate laboratory networks, infection control programs, and policy frameworks to limit dissemination.

Category:Antimicrobial resistance