1. Carbapenem Resistance in Enterobacteriaceae
Jean B. Patel, PhD, (D)ABMM
Leader, Antimicrobial Resistance Team
Division of Healthcare Quality Promotion

2. Carbapenems Drug Route of Administration FDA Status Imipenem IV
Cleared
Meropenem
Ertapenem
IM, IV
Doripenem
Application Submitted

3. Spectrum of Activity + Drug Strep spp. & MSSA Entero-bacteriaeae
Non-fermentors
Anaerobes
Imipenem +
Meropenem
Ertapenem
Limited activity
Doripenem

4. 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
Alcaligenes spp.
Enterobacteriaceae
Mogenella spp.
Serratia spp.
Enterobacter spp.
Citrobacter spp.
ESBL or AmpC + E. coli and Klebsiella spp.
Reference: Sanford Guide

5. 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

6. Carbapenem Resistance: Mechanisms
Enterobacteriaceae
Cephalosporinase + porin loss
Carbapenemase
P. aeruginosa
Porin loss
Up-regulated efflux
Acinetobacter spp.

7. Carbapenemases Classification Enzyme Most Common Bacteria Class A
KPC, SME, IMI, NMC, GES
Enterobacteriaceae
(rare reports in P. aeruginosa)
Class B
(metallo-b-lactamse)
IMP, VIM, GIM, SPM
P. aeruginosa
Enterobacteriacea
Acinetobacter spp.
Class D
OXA

8. Carbapenemases in the U.S.
Enzyme
Bacteria
KPC
Enterobacteriaceae
Metallo-b-lactamase
P. aeruginosa
OXA
Acinetobacter spp.
SME
Serratia marcesens

9. Klebsiella Pneumoniae 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, Citrobacter freundii, Enterobacter spp., Escherichia coli, Salmonella spp., Serratia spp.,
Also reported in Pseudomonas aeruginosa (Columbia)

10. Susceptibility Profile of KPC-Producing K. pneumoniae
Antimicrobial
Interpretation
Amikacin I
Chloramphenicol R
Amox/clav
Ciprofloxacin
Ampicillin
Ertapenem
Aztreonam
Gentamicin
Cefazolin
Imipenem
Cefpodoxime
Meropenem
Cefotaxime
Pipercillin/Tazo
Cetotetan
Tobramycin
Cefoxitin
Trimeth/Sulfa
Ceftazidime
Polymyxin B
MIC >4mg/ml
Ceftriaxone
Colistin
Cefepime
Tigecycline S

11. 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

12. KPC’s in Enterobacteriaceae
Species
Comments
Klebsiella spp.
K. pneumoniae-cause of outbreaks
K. oxytoca-sporadic occurrence
Enterobacter spp.
Sporadic occurrence
Escherichia coli
Salmonella spp.
Citrobacter freundii
Serratia spp.
Pseudomonas aeruginosa – Columbia & Puerto Rico

13. Geographical Distribution of KPC-Producers
Mixed; 29 reported Yes, they conducted some surveillance activity for MRSA; 23 had MRSA reportable in some form and all or selected area.
Frequent Occurrence
Sporadic Isolate(s)

14. Geographical Distribution of KPC-Producers in New Jersey

15. KPC Outside of United States
France (Nass et al AAC 49: )
Singapore (report from survey)
Puerto Rico (ICAAC 2007)
Columbia (Villegas et al AAC 50: & ICAAC 07)
Brazil (ICAAC 2007)
Israel (Navon-Venezia et al AAC 50: )
China (Wei Z, et al AAC 51: )

16. Inter-Institutional & Inter-State Spread of KPC-Producing K. pneumoniae

17. Intra-institution, Interspecies KPC Plasmid Transfer
Cf Ko
Cf Ko

18. Laboratory Detection of KPC-Producers
Problems:
1) Some isolates demonstrate low-level carbapenem resistance
2) Some automated systems fail to detect low-level resistance

19. Susceptibility of KPC-Producers to Imipenem
*12% of isolates test susceptible to imipenem

20. Susceptibility of KPC-Producers to Meropenem
*9% of isolates test susceptible to meropenem

21. Susceptibility of KPC-Producers to Ertapenem
None of the isolates test susceptible to ertapenem

22. Can Carbapenem Susceptibility of I or R Detect KPC-Producers?
Method
Sens/Spec (%) for Detection of KPC-mediated R*
Imipenem
Meropenem
Ertapenem
Ref BMD
94/93
94/98
97/89
Disk Diffusion
42/96
71/96
97/82
Etest
55/96
58/96
90/84
Vitek Legacy
52/98
N/A
Vitek 2
71/98
48/96
MicroScan
74/96
84/98
100/89
Phoenix
81/96
61/98
*N = 76 K. pneum, K. oxy, E. coli; 31 KPC-producers & 45 non-KPC producers

23. CAP Results (D-05) KPC-producing Klebsiella pneumoniae
Susceptible Results
MIC Method
Disk Method
Imipenem 63 57
Meropenem 18
Ertapenem

24. Carbapenem MIC ≥ 2 mg/ml to Detect KPC-producers
Method
Sens/Spec (%) for Detection of KPC-mediated R*
Imipenem
Meropenem
Ertapenem
Ref BMD
100/93
100/89
Etest
84/89
90/87
100/82
Vitek Legacy NA
Vitek 2
71/91
93/89
MicroScan
Phoenix
74/96
87/93
*N = 76 K. pneum, K. oxy, E. coli; 31 KPC-producers & 45 non-KPC producers

25. 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

26. Reading Disk Diffusion & Etest

27. 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,

28. Modified Hodge Test Test isolates Imipenem disk
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,

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

30. 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

31. KPC – Questions
If I have detect KPC-production, should I change susceptible carbapenem results to resistant?
Not enough data to make a clear recommendation
Clinical outcomes data will be necessary

32. Testing Other Drugs 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

33. Testing Other Drugs 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

34. Acknowledgements Fred Tenover Roberta Carey Kamile Rasheed
Kitty Anderson
Brandon Kitchel
Linda McDougal
David Lonsway
Jana Swenson
Arjun Srinivasan
Susan Mikorski