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Carbapenams uses and reistance l.jpg

Dr.T.V.Rao MD

CARBAPENAMS

Uses and Reistance

Dr.T.V.Rao MD


Conventional antibiotics l.jpg

Penicillins

Cephalosporins

Carbapenems

Quinolones

Amino glycosides

Macrolides

Tetracyclines

Nitrofurantoin, metronidazole, clindamycin, vancomycin, teicoplanin, cotrimoxazole, fusidic acid, etc

Isoniazid, pyrazinamide, ethambutol, rifampin, cycloserine, etc

Dr.T.V.Rao MD

Conventional antibiotics


Carbapenems x penicillins l.jpg

Dr.T.V.Rao MD

Carbapenems xpenicillins

  • The carbapenems are structurally very similar to the penicillins, but the sulphur atom in position 1 of the structure has been replaced with a carbon atom, and hence the name of the group, the carbapenem


Antibiotic formulation continue to grow continue to confuse l.jpg

50 penicillins

71 Cephalosporins

12 Tetracyclines

8 amino glycosides

1 monobactam

>3 carbapenems

9 macrolides

2 streptogramins

3 dihydrofolate reductase inhibitors

1 oxazolidinone

5.5 quinolones

Dr.T.V.Rao MD

Antibiotic formulation continue to growCONTINUE TO CONFUSE


A changing landscape for numbers of approved antibacterial agents we have more resistant microbes l.jpg
A Changing Landscape forNumbers of Approved Antibacterial AgentsWe have more resistant Microbes

18

16

14

12

10

Number of agents approved

8

6

4

0

2

0

Dr.T.V.Rao MD

Resistance

1983-87

1988-92

1993-97

1998-02

2003-05

2008

Bars represent number of new antimicrobial agents approved by the FDA during the period listed.

Infectious Diseases Society of America. Bad Bugs, No Drugs. July 2004; Spellberg B et al. Clin Infect Dis. 2004;38:1279-1286;

New antimicrobial agents. Antimicrob Agents Chemother. 2006;50:1912


What are carbapenems l.jpg

Carbapenems are a class of beta-lactam antibiotics with a broad spectrum of antibacterial activity. They have a structure that renders them highly resistant to beta-lactamases. Carbapenem antibiotics were originally developed from thienamycin, a naturally-derived product of Streptomycescattleya.

Dr.T.V.Rao MD

What are carbapenems


Carbapenems common uses l.jpg

Dr.T.V.Rao MD

Carbapenems common uses

  • Imipenem

    • Broad spectrum, covers Gram-positive, Gram-negative (including ESBL-producing strains), Pseudomonas and anaerobes

  • Meropenem

    • Less seizure-inducing potential, can be used to treat CNS infections

  • Ertapenem

    • Lacks activity vs. Acinetobacter and Pseudomonas

    • Has limited activity against penicillin-resistant pneumococci


How are carbapenems used l.jpg

Dr.T.V.Rao MD

How are Carbapenems Used?

Uses by Clinical Syndrome

  • Bacterial meningitis

  • Hospital-associated sinusitis

  • Sepsis of unknown origin

  • Hospital-associated pneumonia

Use by Clinical Isolate

  • Acinetobacter spp.

  • Pseudomonas aeruginosa

  • Alcaligenesspp.

  • Enterobacteriaceae

    • Mogenella spp.

    • Serratia spp.

    • Enterobacter spp.

    • Citrobacter spp.

    • ESBL or AmpC + E. coli and Klebsiellaspp.

Reference: Sanford Guide


Enterobacteriaceae are real problamatic microbes l.jpg

Dr.T.V.Rao MD

Enterobacteriaceae are real problamatic microbes

  • The rapid and disturbing spread of:

    • extended-spectrum ß-lactamases

    • AmpC enzymes

    • carbapenem resistance

      • metallo-β-lactamases

      • KPC and OXA-48 β-lactamases

    • Quinolones resistance


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Dr.T.V.Rao MD

Carbapenems effective on several common isolates

  • Staph (not MRSA), Strep (highly resistant), Neisseria, Haemophilus, Proteus, Pseudomonas, Klebseilla, Bacteroides, anaerobes (excluding C. dif)

  • .


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These agents have the broadest antibacterial spectrum compared to other beta-lactam classes such as penicillins and cephalosporins. Additionally they are generally resistant to the typical bacterial beta-lactamase enzymes which are one of the principal resistance mechanisms of bacteria. They are active against both Gram positive and gram negative bacteria, with the exception of intracellular bacteria, such as the Chlamydia

Dr.T.V.Rao MD

Carbapenems are broad spectrum antibiotic


Drugs belong to the carbapenem class l.jpg

Dr.T.V.Rao MD compared to other beta-

Drugs belong to the carbapenem class:

  • Imipenem

  • Meropenem Ertapenem Doripenem Panipenem/ betamipron Biapenem


Broadest antibacterial spectrum l.jpg

These agents have the broadest antibacterial spectrum compared to other beta-lactam classes such as penicillins and cephalosporins. Additionally they are generally resistant to the typical bacterial beta-lactamase enzymes which are one of the principal resistance mechanisms of bacteria. They are active against both Gram positive and gram negative bacteria, with the exception of intracellular bacteria, such as the Chlamydia.

Dr.T.V.Rao MD

broadest antibacterial spectrum


Carbapenems l.jpg
Carbapenems compared to other beta-lactam classes such as

Dr.T.V.Rao MD


Spectrum of activity l.jpg
Spectrum of Activity compared to other beta-lactam classes such as

Dr.T.V.Rao MD


Carbapenemases l.jpg

  • The most versatile family of compared to other beta-lactam classes such as -lactamases

  • Two major groups based on the hydrolytic mechanism at the active site

    • Serine at the active site: class A and D

    • Zinc at the active site: class B

  • All carbapenemases hydrolyze penicillins, extended spectrum cephalosporins, and carbapenems

Dr.T.V.Rao MD

Carbapenemases


Mechanisms of carbapenem resistance l.jpg

Dr.T.V.Rao MD

Mechanisms of Carbapenem Resistance


Carbapenamases l.jpg
Carbapenamases compared to other beta-lactam classes such as

Dr.T.V.Rao MD


Carbapenamases are complex in mechanisims l.jpg

Carbapenamases constitute the most versatile family of β-lactamases belonging to molecular classes A, B and D and are capable of hydrolyzing almost all β-lactams. Given their zinc dependent hydrolytic activity, Carbapenamases of class B is designated as metallo-ß-lactamases (MBL) that include, for example, IMP, GIM, SIM, SPM, and VIM carbapenemases, and these MBL enzymes have been reported in P.aeruginosa and other multidrug resistant pathogens

Dr.T.V.Rao MD

Carbapenamases are complex in Mechanisims


Carbapenemases20 l.jpg

Dr.T.V.Rao MD β-lactamases belonging to molecular classes A, B and D and are capable of hydrolyzing almost all β-lactams. Given their zinc dependent hydrolytic activity, Carbapenamases of class B is designated as

Carbapenemases

  • Ability to hydrolyze penicillins,cephalosporins, monobactams, and carbapenems

  • Resilient against inhibition by all commercially viableß-lactamase inhibitors

    • Subgroup 2df: OXA (23 and 48) carbapenemases

    • Subgroup 2f : serine carbapenemases from molecular class A: GES and KPC

    • Subgroup 3b contains a smaller group of MBLs that preferentially hydrolyze carbapenems

      • IMP and VIM enzymes that have appeared globally, most frequently in non-fermentative bacteria but also in Enterobacteriaceae


Carbapenamases are spreading faster l.jpg

A new class of bacterial enzymes capable of inactivating Carbapenems, known as Klebsiella pneumoniae Carbapenamases (KPCs), has rapidly spread in the United States and continues to be extensively reported elsewhere in the world. KPCs are class A Carbapenamases that reside on transferable plasmids and can hydrolyze all pencillins, cephalosporins, and Carbapenems.

Dr.T.V.Rao MD

Carbapenamases are spreading faster


Carbapenemases within the enterobacteriaceae l.jpg

KPC carbapenemase Carbapenems, known as

Difficult to detect using current MIC breakpoints.

Isolates that have an MIC of 2 mg/ml to ertapenem or an MIC of 2-4 mg/ml tomeropenem or Imipenem.

Modified Hodge test is confirmatory. Discussed in manual. PCR is gold standard.

Dr.T.V.Rao MD

Carbapenemases within the Enterobacteriaceae


Kpc k pneumoniae c arbapenemase l.jpg

Dr.T.V.Rao MD Carbapenems, known as

KPC (K. pneumoniae carbapenemase)

  • KPCs are the most prevalent of this group of enzymes, found mostly on transferable plasmids in K.pneumoniae

  • Substrate hydrolysis spectrum includescephalosporins and carbapenems


Kpc s in enterobacteriaceae l.jpg
KPC’s in Carbapenems, known as Enterobacteriaceae

Pseudomonas aeruginosa – Columbia & Puerto Rico

Dr.T.V.Rao MD


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Dr.T.V.Rao MD Carbapenems, known as

Pseudomonas aeruginosaCarbapenamases

  • KPC resistance has been reported in inherently resistant organisms such as Pseudomonasfrom Trinidad, an isolate of multidrug-resistant Pseudomonas aeruginosa that harboured a novel KPC-6 gene was detected.


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Dr.T.V.Rao MD Carbapenems, known as

Emerging Carbapenem Resistance in Gram-Negative Bacilli

  • Significantly limits treatment options for life-threatening infections

  • No new drugs for gram-negative bacilli

  • Emerging resistance mechanisms, carbapenemases are mobile,

  • Detection of carbapenemases and implementation of infection control practices are necessary to limit spread


Enterobacteriaceae breakpoints revised so need for other newer drugs may be carbapenms l.jpg
Enterobacteriaceae: Carbapenems, known as Breakpoints revised so need for other newer drugs, may be carbapenms?

Dr.T.V.Rao MD


Resistance to carbapenems l.jpg

Dr.T.V.Rao MD Carbapenems, known as

Resistance to Carbapenems

  • Carbapenems = ertapenem, imipenem, meropenem

  • Intrinsically less susceptibleorganisms – Acinetobacter, P. aeruginosa

  • Other organisms may acquire resistance – K. pneumoniae, other Enterobacteriaceae

  • Know mechanisms of carbapenem resistance:

    • Class A carbapenemases (KPC, SME,…)

    • Class B metallo-β-lactamases (IMP, VIM, SPM…)

    • Class D oxa 23, -40, -51, -58

  • Organisms that acquire these resistance mechanisms will be resistant to all carbapenems but may test susceptible to imipenem


Carbapenemase classification l.jpg
Carbapenemase Classification Carbapenems, known as

Dr.T.V.Rao MD


Emerging metallo lactamases with mobile genetics sentry program 2001 2005 l.jpg
Emerging Carbapenems, known as Metallo-β-Lactamaseswith Mobile Genetics(SENTRY Program 2001-2005)

Dr.T.V.Rao MD


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Dr.T.V.Rao MD Carbapenems, known as

Resistance to Carbapenems

  • Can also have carbapenem resistance due to

    • Class A ESBL’s (CTX-M) + reduced permeability

    • Class C High AmpC + reduced permeability

  • These hydrolyze ertapenem more than meropenem or imipenem


Carbapenemase class a l.jpg

  • First identified 1982 in UK Carbapenems, known as

  • Four major families

  • Chromosomally encoded

    • Serratia marcescens enzyme (SME)

    • Not metalloenzyme carbapenemases (NMC)

    • Imipenem-hydrolyzing -lactamases (IMI)

  • Plasmid encoded

    • Klebsiella pneumoniae carabapenemases (KPC)

    • Guiana Extended-Spectrum (GES)

Dr.T.V.Rao MD

Carbapenemase Class A


Class a carbapenemases l.jpg

Dr.T.V.Rao MD Carbapenems, known as

Class A Carbapenemases

  • K. pneumoniae carbapenemase (KPC-type) possess carbapenem-hydrolyzing enzymes most common on East Coast of U.S.

  • Enzymes are capable of efficiently hydrolyzing penicillins, Cephalosporins, aztreonam, and carbapenems and are inhibited by clavulanic acid and tazobactam

  • To date 4 KPC enzymes have been identified: KPC-1, KPC-2, KPC-3, KPC-4 – E. coli, K. pneumoniae, K. oxytoca, E. cloacae


Carbapenemase producing klebseilla pneumonia kpc l.jpg

Dr.T.V.Rao MD Carbapenems, known as

Carbapenemase-Producing Klebseilla pneumonia (KPC)

  • KPC-3 is the most recently reported enzyme in that group

  • KPC-3 is closely related to its predecessors, differing by only 1 amino acid from KPC-2 and by 2 amino acids from KPC-1

  • It has been recovered from isolates of K. pneumoniae, E. coli, and E. cloacae


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Carbapenem Resistance: Mechanisms Carbapenems, known as

Dr.T.V.Rao MD


Carbapenemases36 l.jpg
Carbapenemases Carbapenems, known as

Dr.T.V.Rao MD


K lebsiella p neumoniae and c arbapenemase l.jpg

Dr.T.V.Rao MD Carbapenems, known as

KlebsiellaPneumoniae and Carbapenemase

  • KPC is a class A b-lactamase

    • Confers resistance to all b-lactams including extended-spectrum cephalosporins and carbapenems

  • Occurs in Enterobacteriaceae

    • Most commonly in Klebsiella pneumoniae

    • Also reported in: K. oxytoca, Citrobacterfreundii, Enterobacter spp., Escherichia coli, Salmonella spp., Serratia spp.,

  • Also reported in Pseudomonas aeruginosa (Columbia)


Kpc enzymes l.jpg

Dr.T.V.Rao MD Carbapenems, known as

KPC Enzymes

  • Located on plasmids; conjugative and nonconjugative

  • blaKPC is usually flanked by transposon sequences

  • blaKPC reported on plasmids with:

    • Normal spectrum b-lactamases

    • Extended spectrum b-lactamases

    • Aminoglycoside resistance


Kpc enzymes39 l.jpg

  • Molecular class A and functional group 2f Carbapenems, known as

  • Inhibited by clavulanic acid but not by EDTA

  • Confers resistance to ALL -LACTAM antibiotics

  • Plasmid-encoded

    • Associated with other resistant genes (aminoglycosides, fluoroquinolones)

    • Transferable

Dr.T.V.Rao MD

KPC Enzymes


Kpc epidemiology l.jpg

Predominantly in Carbapenems, known as K. pneumoniae (KP)

Reported in Enterobacter spp., Salmonella spp., E. coli, P. aeruginosa, and Citrobacter spp.

First identified in KP clinical isolate from North Carolina in 1996 (KPC-1)

KPC-2, -3, and -4 have been reported.

Mostly identified on the East cost

Dr.T.V.Rao MD

KPC Epidemiology


Kpc epidemiology41 l.jpg

  • KPC producers have been identified outside USA Carbapenems, known as

    • France

    • Brazil

    • Columbia

    • China

  • Not detected at the University of Nebraska Medical Center

    • 45 ESBL-like isolates collected-6 had elevated carbapenem MICs-none contained KPC

Dr.T.V.Rao MD

KPC Epidemiology


K pneumoniae with carbapenemase producing clones l.jpg
K. Pneumoniae with Carbapenems, known as carbapenemase-producing clones

Dr.T.V.Rao MD

Norman P et al. LID 2009


Carbapenemases within the enterobacteriaceae43 l.jpg

KPC carbapenemase Carbapenems, known as

Difficult to detect using current MIC breakpoints.

Isolates that have an MIC of 2 mg/ml to ertapenem or an MIC of 2-4 mg/ml tomeropenem or Imipenem.

Modified Hodge test is confirmatory. Discussed in manual. PCR is gold standard.

Dr.T.V.Rao MD

Carbapenemases within the Enterobacteriaceae


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Major families of β-lactamases of clinical importance Carbapenems, known as

Dr.T.V.Rao MD

Bush K and Jacboy G AAC 2010


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Dr.T.V.Rao MD Carbapenems, known as

When to Suspect a KPC-Producer

  • Enterobacteriaceae – especially Klebsiella pneumoniae that are resistant to extended-spectrum cephalosporins:

    • MIC range for 151 KPC-producing isolates

      • Ceftazidime 32 to >64 mg/ml

      • Ceftriaxone ≥ 64 mg/ml

      • Cefotaxime ≥ 64 mg/ml

    • Variable susceptibility to cefoxitin and cefepime


Newer carbapenemases l.jpg
Newer Carbapenemases Carbapenems, known as

  • As of June 2010, there were three reported cases of Enterobacteriaceae isolates bearing this newly described resistance mechanism in the US, the CDC stated that "All three U.S. isolates were from patients who received recent medical care in India."


Cdc reports the new genetic mechanisms l.jpg

The isolate, Klebseilla pneumoniae 05-506, was shown to possess a metallo-beta-lactamase (MBL) but was negative for previously known MBL genes. Gene libraries and amplification of class 1 integrons revealed three resistance-conferring regions; the first contained bla(CMY-4) flanked by ISEcP1 and blc. The second region of 4.8 kb contained a complex class 1 integron with the gene cassettes arr-2, a new erythromycin esterase gene; ereC; aadA1; and cmlA7

CDC reports the new genetic mechanisms


Genetic origin of the ndm 1 l.jpg

An intact ISCR1 element was shown to be downstream from the qac/sul genes. The third region consisted of a new MBL gene, designated bla(NDM-1), flanked on one side by K. pneumoniae DNA and a truncated IS26 element on its other side. The last two regions lie adjacent to one another, and all three regions are found on a 180-kb region that is easily transferable to recipient strains and that confers resistance to all antibiotics except fluoroquinolones and colistin. NDM-1 shares very little identity with other MBLs, with the most similar MBLs being VIM-1/VIM-2, with which it has only 32.4% identity.

Genetic origin of the NDM-1


Molecular configuration of ndm 1 l.jpg

NDM-1 also has an additional insert between positions 162 and 166 not present in other MBLs. NDM-1 has a molecular mass of 28 kDa, is monomeric, and can hydrolyze all beta-lactams except aztreonam. Compared to VIM-2, NDM-1 displays tighter binding to most Cephalosporins.

Molecular configuration of NDM-1


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Compared to VIM-2, NDM-1 displays tighter binding to most cephalosporins, in particular, cefuroxime, cefotaxime, and cephalothin (cefalotin), and also to the penicillins. NDM-1 does not bind to the carbapenems as tightly as IMP-1 or VIM-2 and turns over the carbapenems at a rate similar to that of VIM-2. In addition to K. pneumoniae 05-506, bla(NDM-1) was found on a 140-kb plasmid in an Escherichia coli strain isolated from the patient's feces, inferring the possibility of in vivo conjugation

NDM genetic coding differs from other recent isolates


Bla ndm 1 is expressed in l.jpg
bla cephalosporins, in particular, NDM-1 is expressed in...

  • Isolates, which include an Escherichia coli, Klebsiella pneumoniae, and Enterobacter cloacae, carry blaNDM-1, which confers resistance to all beta-lactam agents except aztreonam (a monobactam antimicrobial) ; all three isolates were aztreonam resistant, presumably by a different mechanisms.


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Dr.T.V.Rao MD cephalosporins, in particular,

Phenotypic Tests for Carbapenemase Activity

  • Modified Hodge Test

    • 100% sensitivity in detecting KPC; also positive when other carbapenemases are present

    • 100% specificity

Procedure described by Lee et al. CMI, 7, 88-102. 2001.


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CLSI has published guidelines for detection of isolates producing carbapenemases (CLSI document M100) . For isolates that test susceptible to a carbapenem but demonstrate reduced susceptibility either by disk diffusion or MIC testing, performing a phenotypic test for carbapenemase activity, the Modified Hodge Test (MHT), is recommended

Dr.T.V.Rao MD

CLSI guidelines for Carbapenamases detection


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Dr.T.V.Rao MD producing carbapenemases

Modified Hodge Test

Lawn of E. coli ATCC 25922

1:10 dilution of a

0.5 McFarland suspension

Test isolates

Imipenem disk

Described by Lee et al. CMI, 7, 88-102. 2001.


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Dr.T.V.Rao MD producing carbapenemases

Modified Hodge Test

  • Preliminary results suggest that any of the three carbapenem disks work in the Modified Hodge Test


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Dr.T.V.Rao MD producing carbapenemases


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Dr.T.V.Rao MD producing carbapenemases

Indian data on Carbapenem resistance

  • Incidence of Meropenem resistance higher than that of Imipenem/cilastatin across clinically significant nosocomial pathogens

Gupta E et al, Indian J Med Res 2006 July; 124: 95-98


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Dr.T.V.Rao MD producing carbapenemases

Indian data on Carbapenem resistance

  • Overall Imipenem/cilastatin showed better activity than Meropenem

Gupta E et al, Indian J Med Res 2006 July; 124: 95-98


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Dr.T.V.Rao MD

Mechanisms of Carbapenem Resistance


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Dr.T.V.Rao MD producing carbapenemases

What Labs Should Do Now

  • Look for isolates of Enterobacteriaceae (especially K. pneumoniae), with carbapenem MIC ≥ 2 mg/ml or nonsusceptible to ertapenem by disk diffusion

  • Consider confirmation by Modified Hodge Test

  • Can submit initial isolate to CDC via NJ State Lab for confirmation by blaKPC PCR if KPC-producers not previously identified in hospital’s isolate population

  • Alert clinician and infection control practitioner to possibility of mobile carbapenemase in isolate


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  • First identified 1982 in UK producing carbapenemases

  • Four major families

  • Chromosomally encoded

    • Serratia marcescens enzyme (SME)

    • Not metalloenzyme carbapenemases (NMC)

    • Imipenem-hydrolyzing -lactamases (IMI)

  • Plasmid encoded

    • Klebsiella pneumoniae carabapenemases (KPC)

    • Guiana Extended-Spectrum (GES)

Dr.T.V.Rao MD

Carbapenemases Class A


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Predominantly in producing carbapenemases K. pneumoniae (KP)

Reported in Enterobacter spp., Salmonella spp., E. coli, P. aeruginosa, and Citrobacter spp.

First identified in KP clinical isolate from North Carolina in 1996 (KPC-1)

KPC-2, -3, and -4 have been reported.

Mostly identified on the East cost

Dr.T.V.Rao MD

KPC Epidemiology


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Enterobacteriaceae producing carbapenemases

Resistance to extended spectrum Cephalosporins (cefotaxime, ceftazidime, and ceftriaxone)

Variable susceptibility to cephamycins (cefoxitin, cefotetan)

Carbapenem MICs  2 g/ml

Dr.T.V.Rao MD

When to Suspect a KPC Producer


How to detect a kpc producer l.jpg

  • Antimicrobial susceptibility tests (ASTs) producing carbapenemases

    • MIC

      • Carbapenem MIC  2 g/ml

    • Disk diffusion

      • Carbapenem: “I” or “R”

    • Among carbapenems, ertapenem:

      • Most sensitive

      • less specific

Dr.T.V.Rao MD

How to Detect a KPC Producer

  • Anderson et al. 2007. JCM 45 (8): 2723


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Definitive Identification of a KPC Producer producing carbapenemases

  • Modified Hodge test

    • 100% sensitivity to detect KPC

  • Swab E. coli ATCC 25922 onto plate to create lawn Place imipenem disk in center.

  • Streak test isolates from edge of disk to end of plate.

  • Incubate overnight.

  • Look for growth of E. coli around test isolate streak - indicates carbapenem-hydrolyzing enzyme.

pos

pos

pos

neg

neg

neg

meropenem

ertapenem

imipenem

Dr.T.V.Rao MD

Janet Hindler, What’s New in the 2008 CLSI Standards for (AST)?


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Dr.T.V.Rao MD producing carbapenemases

K. Pneumoniae with KPC-2


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Dr.T.V.Rao MD producing carbapenemases

Tris/EDTA Disk Test

  • Tris/EDTA disks used in combination with a carbapenem disk provides a sensitive test for class A carbapenem-hydrolyzing enzymes

  • Imipenem disks most sensitive carbapenem disks to use with this method, but ertapenem and meropenem also work well


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Dr.T.V.Rao MD producing carbapenemases

Tris/EDTA Disk Test

  • KPC-2 producing K. pneumoniae is both the lawn culture and inoculated onto Tris/EDTA disk placed beside imipenem disk.

  • Indentation indicates production of carbapenem-hydrolyzing enzyme (positive test).

  • Second Tris/EDTA disk (not inoculated with test organism) is placed further away from imipenem disk to test for metallo-β-lactamase production (negative test).

Procedure described by Ellen Molan and Ken Thompson, Creighton University


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Dr.T.V.Rao MD producing carbapenemases

Imipenem resistant K. pneumoniae expressing Class A carbapenemase and Imipenem resistant S. maltophilia expressing Class B carbapenemase


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Dr.T.V.Rao MD producing carbapenemases

Modified Hodge Test

  • Inoculate MH agar with a 1:10 dilution of a 0.5 McFarland suspension of E. coli ATCC 25922 and streak for confluent growth using a swab.

  • Place 10-µg imipenem disk in center

  • Streak each test isolate from disk to edge of plate

  • Isolate A is a KPC producer and positive by the modified Hodge test.

Anderson KF et al. JCM 2007 Aug;45(8):2723-5.


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Dr.T.V.Rao MD producing carbapenemases

KPC Producer - Example

imipenem

≤4 µg/ml*

meropenem

≤4 µg/ml*

ertapenem

≤2 µg/ml*

*CLSI breakpoint for “S”;

marked w/ arrow

Courtesy of J. Patel, PhD., CDC


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E. cloacae: ertapenem resistance, meropenem susceptible producing carbapenemases

Dr.T.V.Rao MD


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E. cloacae derepressed mutant expressing AmpC and porin mutation

Dr.T.V.Rao MD

KPC positive Control

Patient Isolate


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Activity against Acinetobacter spp. mutation

  • Carbapenems are considered the drugs of choice for treating serious infections caused by Acinetobacter baumanii

  • Progressive antimicrobial resistance in Acinetobacter is a cause of concern

  • Imipenem/cilastatin demonstrates lower MICs and lower resistance rates than Meropenem against Acinetobacter baumanii

Dr.T.V.Rao MD

Canduela MJ et al, J AntimocrobChemother 2006; 57: 1220-1222


Alternative treatment for a kpc producer l.jpg

  • Minocycline

  • A strategy for susceptibility testing is needed

  • Dr.T.V.Rao MD

    Alternative Treatment for a KPC Producer


    Carbapenemase producing klebseilla pneumonia kpc77 l.jpg

    Dr.T.V.Rao MD mutation

    Carbapenemase-Producing Klebseilla pneumonia (KPC)

    • Conclusions:

      • Correct inoculum's of any organism undergoing identification and susceptibility testing should be assured

      • K. pneumoniae intermediate or resistant to ertapenem or meropenem should be considered resistant to all carbapenems, regardless of the other susceptibility results

      • Inoculum effect with imipenem has also been observed in KPC-possessing Enterobacter spp.

    Bratu, S. et al AAC 49:3018-3020, 2005


    Clsi guidelines to be followed in detection l.jpg

    • ESBL detection—CLSI guidelines present mutation

      • Need to have guidelines to detect ESBLs present in other species besides E. coli, K. pneumoniae, K. oxytoca, and P. mirabilis.

    • AmpC detection-No guidelines available

    • KPC detection-Not widespread, need to have lower concentrations of carbapenems on panels.

    Dr.T.V.Rao MD

    Clsi guidelines to be followed in detection


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    Dr.T.V.Rao MD mutation

    Purchase QC strains

    • ATCC BAA-1708- mupA S. aureus isolate, ATCC BAA-1705 and BAA-1706. Positive and Negative modified Hodge test isolates, respectively.

    • New ampicillin, piperacillin and ticarcillin QC tests for E. coli ATCC35218.


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    Dr.T.V.Rao MD mutation

    Definitive Identification of a KPC Producer

    • PCR

      • The method of choice to confirm KPC


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    Dr.T.V.Rao MD mutation

    Automated Systems cannot detect all types of antibiotic resistance

    • Limitations of Automated Systems in detecting emerging resistance in Gram-Negative Bacilli

      • Unable to detect ESBLs in organisms other than E. coli and Klebsiella

      • Unable to detect Inducible AmpC

      • Unable to detect ESBLs in AmpC positive strains

      • Unable to detect imipenem resistance in strains producing KPC carbapenemases


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    Dr.T.V.Rao MD mutation

    Carbapenems: Myths and Reality

    • Inspite of expensiveness of Carbapenems, pharmacoeconomic studies have demonstrated the advantages of these drugs over a number of cheaper conventional antibiotics

    • Since inadequate empirical antimicrobial therapy is associated with significantly higher mortality in serious infections, Carbapenems are no longer considered second-line antimicrobials

    • The main ways to improve use of Carbapenems is:

      - De escalation therapy

      - Optimal dosing of Carbapenems

    Bereznyakov IG, Kharkov Medical Academy of Post Graduate Education, Kharkov, Ukraine


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    Dr.T.V.Rao MD mutation

    Testing Other Drugs for clinical use in carbapenem resistant strains

    • Polymixin B or Colistin

      • Could test either, but colistin used clinically

      • Disk diffusion test does not work – don’t use!

      • Etest – works well, but not FDA cleared

      • Broth microdilution – reference labs

      • Breakpoints - none

        • MIC ≤ 2 mg/ml, normal MIC range

        • MIC ≥ 4 mg/ml indicates increased resistance


    Testing other drugs to treat patients with resistant carbapenem isolates l.jpg

    Dr.T.V.Rao MD mutation

    Testing Other Drugs to treat patients with resistant carbapenem isolates

    • Tigecycline:

      • Test by Etest if possible – disk diffusion tends to overcall resistance

      • No CLSI breakpoint, but there are FDA breakpoint

        • Susceptible ≤ 2 mg/ml

        • Intermediate = 4 mg/ml

        • Resistant ≥ 8 mg/ml


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    Each laboratory should have a staff member with the time, interest, and expertise to provide leadership in antibiotic testing and resistance. This person would read relevant publications, network with other laboratories, and evaluate potentially useful tests to detect new forms of resistance before new CLSI-recommended tests become available”

    Ken Thomson, Emerging Infect. Dis., 2001

    Dr.T.V.Rao MD

    How to improve our microbiology departments


    Interpretation results conveyed to infection control departments l.jpg

    Dr.T.V.Rao MD interest, and expertise to provide leadership in antibiotic testing and resistance. This person would read relevant publications, network with other laboratories, and evaluate potentially useful tests to detect new forms of resistance before new

    Interpretation/ResultsConveyed to Infection Control Departments

    • Report all cultures that are positive for CRE or carbapenemase-producing Enterobacteriaceae to the appropriate infection control personnel.


    Inspite of several advances simeple hand wash can save several lives l.jpg

    Dr.T.V.Rao MD interest, and expertise to provide leadership in antibiotic testing and resistance. This person would read relevant publications, network with other laboratories, and evaluate potentially useful tests to detect new forms of resistance before new

    INSPITE OF SEVERAL ADVANCES SIMEPLE hand WASH CAN SAVE SEVERAL LIVES


    The programme designed with references l.jpg

    • Livermore et. al. 2001. Interpretive reading: recognizing the unusual and inferring resistance mechanisms from resistance phenotypes. J AntimicrobChemother. 48:S1, 87-102.

    • Paul C. Schreckenberger, Ph.D., D(ABMM) Professor of Pathology

      Director, Clinical Microbiology Laboratory Loyola University Medical Center

      Ken Thomson, Emerging Infect. Dis., 2001

      Gupta E et al, Indian J Med Res 2006 July; 124: 95-98

      Bratu S et al AAC 49:776-778; Schreckenberger, P personal observation

      Canduela MJ et al, J AntimocrobChemother 2006; 57: 1220-1222

      Lee et al. CMI, 7, 88-102. 2001.

    Dr.T.V.Rao MD

    The programme designed with references



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