K p C

KPC

Klebsiella pneumoniae Carbapenemases

Image credit: National Institute of Allergy and Infectious Diseases (NIAID)

human neutrophil

Carbapenem-resistantKlebsiella pneumoniae

Cephalosporin

PenicillinAztreonam

β-Lactam Ring

β-Lactam Antibiotics

e.g. Imipenem, Meropenem

Highly resistant to most β-Lactams including ESBLs

Broad-spectrum antibiotics

Last resort against ESBL–producing Enterobacteriaceae& MDR Gram-negative bacilli

Active

Carbapenemases

Hydrolyze penicillins, cephalosporins, monobactams, and carbapenems.

β-Lactamases

Inactive Image Source: Trends in Molecular Medicine

β-

1—4

Based on the substrate profile

Molecular ClassificationBush-Jacoby-Medeiros Classification

(BJM)

A—D

Based on the enzyme structure

Functional ClassificationAmbler's Classification

Classification of beta-lactamases

BJM systemMajor

subgroupsAmbler System Main attributes

Group 1 cephalosporinases – C (cephalosporinases)Usually chromosomal; Resistance to all β-lactams except carbapenems; Not inhibitedby clavulanate

Group 2 penicillinases 2a A (serine β-lactamases) Staphylococcal penicillinases

(clavulanic acid susceptible) 2b A Broad-spectrum – TEM-1, TEM-2, SHV-1

2be A Extended-spectrum – TEM-3–160, SHV-2–101

2br A Inhibitor resistant TEM (IRT)

2c A Carbenicillin-hydrolyzing

2e A Cephalosporinases inhibited by clavulanate

2f A Carbapenemases inhibited by clavulanate

2d D(oxacillin-hydrolyzing) Cloxacillin-hydrolyzing (OXA)

Group 3 metallo-β-lactamase 3a B (metalloenzymes) Zinc-dependent carbapenemases

3b B

3c B

Group 4 Not classified Misc enzymes, most not yet sequenced

Perez, Federico, et al. "The continuing challenge of ESBLs." Curr opin pharm 7.5 (2007): 459-469.

KPC

Classification of beta-lactamases

KPC

Ambler Class A Serine β-lactamase, BMJ group 2f

First discovered in a Klebsiella pneumonia—North Carolina, US (1996) – KPC1

Klebsiella pneumoniae Carbapenemases

Later found in other genera of the Enterobacteriaceae familyKlebsiella oxytocaCitrobacter freundiiEnterobacter aerogenes & E. Cloacae

Also in Pseudomonas aeruginosa & Acinetobacter baumannii

Escherichia coliSerratia marcescens

KPC

16 variants (KPC-2 to KPC-17)—Most frequent KPC-2 and KPC-3

The most clinically significant enzymes of the class A carbapenemases

Klebsiella pneumoniae Carbapenemases

Clinical detection—often challenging

Hydrolyze β-lactams of all classes

PenicillinsAll cephalosporinsMonobactamsCarbapenems

and β-lactamase inhibitors

Multidrug resistant—High mortality rates

Greatest potential for spread—Located on plasmids

KPC

Queenan, Anne Marie, and Karen Bush. "Carbapenemases: the versatile β-lactamases." Clinical microbiology reviews 20.3 (2007): 440-458.

Emergence ofclass A carbapenemases

KPC-1

Munoz-Price, L. Silvia, et al. "Clinical epidemiology of the global expansion of Klebsiella pneumoniae carbapenemases." The Lancet infectious diseases 13.9 (2013): 785-796.

KPC

Antibiotic sensitivity tests—inconsistent results

Carbapenemases alone doesn’t produce compete resistance.

Some KPC-producers are susceptible to carbapenems.

Variable levels of carbapenem resistance

Insufficient cell numbers Imipenem or Meropenem is not sensitive enough.

Ertapenem —best so far

But ertapenem resistance by itself is not a marker for KPC expression.

Confirmatory tests are necessary. Modified Hodge Test

Molecular tools should become the gold standard.

Sensitivity varies with the substrate

KPC

E.coli ATCC 25922 suspension in broth/saline

Diluted 1:10

Spread on a MHA plate

Place 10 μg antibiotic disk in the center

Streak test organism(s)

Incubation overnight at 35⁰C ± 2 ⁰ C

Susceptible to carbapenems

KPCE.coli ATCC 25922

Bora, Arijit, et al. "Incidence of metallo-beta-lactamase producing clinical isolates of Escherichia coli and Klebsiella pneumoniae in central Nepal." BMC research notes 7.1 (2014): 557.

Test organism secretes KPC and inactivates the antibiotic.

E. Coli grows along the edges.

clover leaf-typeindentation

No E.coli growthTest organism doesn’t secrete KPC.

Antibiotic remains active.E. Coli growth inhibited.

KPC

• Perez, Federico, et al. "The continuing challenge of ESBLs." Current opinion in pharmacology 7.5 (2007): 459-469.

• Queenan, Anne Marie, and Karen Bush. "Carbapenemases: the versatile β-lactamases." Clinical microbiology reviews 20.3 (2007): 440-458.

• Robledo, Iraida E., Edna E. Aquino, and Guillermo J. Vázquez. "Detection of the KPC gene in Escherichia coli, Klebsiella pneumoniae, Pseudomonas

aeruginosa, and Acinetobacter baumannii during a PCR-based nosocomial surveillance study in Puerto Rico." Antimicrobial agents and

chemotherapy55.6 (2011): 2968-2970.

• Sacha, Paweł, et al. "The KPC type beta-lactamases: new enzymes that confer resistance to carbapenems in Gram-negative bacilli." Folia

Histochemica et Cytobiologica 47.4 (2009): 537-543.

• Wang, Dongguo, et al. "Phenotypic and Enzymatic Comparative Analysis of the KPC Variants, KPC-2 and Its Recently Discovered Variant KPC-15."

(2014): e111491.

• Walther-Rasmussen, Jan, and Niels Høiby. "Class A carbapenemases."Journal of antimicrobial chemotherapy 60.3 (2007): 470-482.

• Yigit, Hesna, et al. "Novel carbapenem-hydrolyzing β-lactamase, KPC-1, from a carbapenem-resistant strain of Klebsiella

pneumoniae." Antimicrobial agents and chemotherapy 45.4 (2001): 1151-1161.

• Yigit, Hesna, et al. "Novel carbapenem-hydrolyzing β-lactamase, KPC-1, from a carbapenem-resistant strain of Klebsiella

pneumoniae." Antimicrobial agents and chemotherapy 52.2 (2008): 809.