Presentation from the 3rd Joint Meeting of the Antimicrobial Resistance and Healthcare-Associated Infections (ARHAI) Networks, organised by the European Centre of Disease Prevention and Control - Stockholm, 11-13 February 2015

1. ECDC EARS-Net
External Quality Assessment
(EQA) 2014
Derek Brown
Peterborough (UK)
EUCAST Scientific Secretary
UK NEQAS Antimicrobial Susceptibility Testing Specialist Advisory Group
Christine Walton and Shila Seaton
UK NEQAS for Microbiology, Colindale, London (UK)
UK NEQAS

2. Objectives of EARS-Net
External Quality Assessment
• To assess the accuracy of antimicrobial
susceptibility test results reported by laboratories
• To assess the comparability of routine
antimicrobial susceptibility test results between
laboratories and countries
• Education

3. Participation in EARS-Net EQA
2014 2013 2012 2011 2010
Countries 31 30 30 31 31
Laboratories 905 872 880 911 873
Laboratories
responding
93% 92% 92% 90% 88%

4. Guidelines used in EARS-Net EQA 2014
0
10
20
30
40
50
60
70
80
90
AT BE BG CY CZ DE DK EE ES FI FR GR HR HU IE IS IT LT LU LV MT NL NO PL PT RO SE SI SK UK
EUCAST CLSI DIN SFM BSAC
Country
No.ofparticipants

5. Trends in antimicrobial susceptibility
testing guidelines in EARS-Net
0
10
20
30
40
50
60
70
80
90
2010 2011 2012 2013 2014
Percentparticipants
CLSI
All EUCAST
EUCAST
EUCAST-based

6. Methods use in EARS-Net EQA 2014
Guideline Automated Disk MIC OTHER Total % guideline
BSAC 2 9 0 2 13 1.5
DIN 0 0 1 0 1 0.1
EUCAST 312 239 51 3 605 72.2
CLSI 100 58 6 0 164 19.6
SFM 20 35 0 0 55 6.6
Total 434 341 58 5 838 100
% method 51.8 40.7 6.9 0.6 100

7. Escherichia coli specimen 2486
CTX-M-15 ESBL
Antimicrobial agent Reference MIC (mg/L) EUCAST CLSI
Amoxicillin ≥128 R R
Ampicillin ≥128 R R
Cefotaxime ≥128 R R
Ceftazidime 32-64 R R
Ceftriaxone ≥128 R R
Amoxicillin-clavulanic acid ≥128 (64) R R
Piperacillin-tazobactam 32-64 R I
Imipenem 0.12-0.25 S S
Meropenem 0.03 S S
Doripenem S S
Ertapenem 0.12-0.25 S S
Ciprofloxacin ≥128 R R
Gentamicin ≥128 R R
Tobramycin ≥128 R R
Amikacin 16 I S

8. 0
20
40
60
80
100
%Concordance
Antimicrobial agent
Escherichia coli specimen 2486

9. Escherichia coli specimen 2486
Amoxicillin-clavulanic acid resistant
MICs ≥ 128 mg/L (fixed 2 mg/L clavulanic acid)
64 mg/L (2:1 ratio amox:clav)
EUCAST breakpoints S ≤8, R >8 mg/L (fixed clav 2 mg/L)
CLSI breakpoints S ≤8, R ≥ 32 mg/L (2:1 ratio amox:clav)
• Tendency to reporting intermediate with CLSI method
Guideline n %S %I %R
EUCAST 623 1.1 2.7 96.1
CLSI 166 2.4 27.1 70.5

10. Escherichia coli specimen 2486
Piperacillin-tazobactam MICs 32-64 mg/L
EUCAST resistant ( breakpoints S ≤8, R >16 mg/L)
CLSI intermediate (breakpoints S ≤16, R ≥ 128 mg/L)
• High discrepancy rate in reporting with all guidelines
• High discrepancy rate with all methods
Guideline n %S %I %R
EUCAST 646 38.9 28.5 32.6
CLSI 163 59.5 28.2 12.3
Guideline, method n %S %I %R
EUCAST, disk diffusion 274 27.4 38.3 34.3
EUCAST, automated 322 48.1 20.2 31.7
CLSI, disk diffusion 55 63.6 29.1 7.3
CLSI, automated 98 58.2 26.5 15.3

11. Escherichia coli specimen 2486
Amikacin MIC 16 mg/L
EUCAST intermediate ( breakpoints S ≤8, R >16 mg/L)
CLSI susceptible (breakpoints S ≤16, R ≥ 64 mg/L)
• High discrepancy rate in reporting with all guidelines, partly
in line with breakpoints
Guideline n %S %I %R
EUCAST 579 56.8 38.7 4.5
CLSI 153 80.4 17.0 2.6

12. Escherichia coli specimen 2486
Amikacin MIC 16 mg/L
EUCAST intermediate ( breakpoints S ≤8, R >16 mg/L)
CLSI susceptible (breakpoints S ≤16, R ≥ 64 mg/L)
• With EUCAST guidelines more discrepancies with disk
diffusion method
Guideline, method n %S %I %R
EUCAST, disk diffusion 242 80.6 16.9 2.5
EUCAST, automated 282 34.0 61.4 4.6
CLSI, disk diffusion 56 83.9 10.7 5.4
CLSI, automated 91 78.0 19.8 2.2

13. Klebsiella pneumoniae specimen 2487
VIM carbapenemase
Antimicrobial agent Reference MIC (mg/L) EUCAST CLSI
Amoxicillin ≥128 R R
Ampicillin ≥128 R R
Cefotaxime ≥128 R R
Ceftazidime ≥128 R R
Ceftriaxone ≥128 R R
Amoxicillin-clavulanic acid ≥128 (64) R R
Piperacillin-tazobactam ≥128 R R
Imipenem 64 R R
Meropenem ≥128 R R
Doripenem R R
Ertapenem ≥128 R R
Ciprofloxacin ≥128 R R
Gentamicin 1 S S
Tobramycin 16 R R
Amikacin 16 I S

14. 0
20
40
60
80
100
%Concordance
Antimicrobial agent
Klebsiella pneumoniae specimen 2487

15. Klebsiella pneumoniae specimen 2487
Amikacin MIC 16 mg/L
Aminoglycoside susceptibility was typical for an organism
producing AAC(6')I, i.e.
Gentamicin susceptible (MIC 1 mg/L)
Tobramycin resistant (MIC 16 mg/L)
Amikacin borderline (MIC 16 mg/L)
EUCAST intermediate (breakpoints S ≤8, R >16 mg/L)
CLSI susceptible (breakpoints S ≤16, R ≥ 64 mg/L)
• High discrepancy rate in reporting with all guidelines,
partly in line with breakpoints
Guideline n %S %I %R
EUCAST 590 8.0 62.3 28.8
CLSI 156 33.3 48.7 18.0

16. Klebsiella pneumoniae specimen 2487
Amikacin MIC 16 mg/L
• More discrepancies with disk diffusion method
• EUCAST expert rule note that acquired AAC(6')I may not
confer phenotypic resistance to amikacin despite
modification of amikacin, and that such organisms should
be reported intermediate even if they appear susceptible.
Some participants may have edited S test results to I.
Guideline, method n %S %I %R
EUCAST, disk diffusion 246 13.4 53.7 32.9
EUCAST, automated 289 3.5 73.7 22.8
CLSI, disk diffusion 56 23.2 44.6 32.1
CLSI, automated 94 38.3 51.1 10.6

17. Staphylococcus aureus specimen 2489
VISA
Antimicrobial agent Reference MIC (mg/L) EUCAST CLSI
Penicillin 64 R R
Cefoxitin ≥128 R R
Oxacillin ≥128 R R
Vancomycin 4 R I
Teicoplanin 8-16 R S/I
Erythromycin ≥128 R R
Clindamycin ≥128 R R
Gentamicin 128 – 256 R R
Fusidic acid 0.06 - 0.12 S -
Ciprofloxacin 16 R R
Rifampicin ≥128 R R
Tetracycline 64 R R

18. 0
20
40
60
80
100
%Condordance
Antimicrobial agents
Staphylococcus aureus specimen 2489

19. Staphylococcus aureus specimen 2489
Vancomycin resistance
MIC 4 mg/L
EUCAST resistant ( breakpoints S ≤ 2, R > 2 mg/L)
CLSI intermediate (breakpoints S ≤ 2, R ≥ 16 mg/L)
• High error rate in reporting with all guidelines
Guideline n %S %I %R
EUCAST 655 45.8 2.4 51.8
CLSI 164 57.3 39.0 3.7

20. Staphylococcus aureus specimen 2489
Vancomycin resistance
• No testing method was reliable
• Disk diffusion should not be used
Method n % reporting
S
Disk diffusion only 16 87.5
MIC 370 41.4
Automated 430 50.5

21. Staphylococcus aureus specimen 2489
Teicoplanin resistance
MIC 8-16 mg/L
EUCAST resistant ( breakpoints S ≤ 2, R >2 mg/L)
CLSI susceptible/intermediate (breakpoints S ≤8, R ≥32 mg/L)
• Reporting in line with guidelines
Guideline n %S %I %R
EUCAST 573 7.2 1.0 91.8
CLSI 147 47.0 43.5 9.5

22. Streptococcus pneumoniae specimen 2489
Penicillin “intermediate”
Antimicrobial agent Reference MIC (mg/L) EUCAST CLSI
Oxacillin screen R R
Penicillin:
meningitis
pneumonia
0.25 – 0.5 I
R
S
R
S
Cefotaxime
meningitis
pneumonia
0.06 -0.12
S
S
S
S
Ceftriaxone
meningitis
pneumonia
0.12 – 0.25
S
S
S
S
Levofloxacin 1 S S
Moxifloxacin 0.12 S S
Norfloxacin S S
Erythromycin ≥128 R R
Clindamycin R R

23. 0
20
40
60
80
100
%Concordance
Antimicrobial agents
Streptococcus pneumoniae specimen 1378

24. Streptococcus pneumoniae specimen 2489
Benzylpenicillin MIC 0.25 – 0.5 mg/L
Oxacillin screen resistant
• No intermediate category
• Reference zone diameter 12mm
Guideline n %S %I %R
EUCAST 403 8.9 5.0 86.1
CLSI 84 7.1 2.4 90.5

25. Streptococcus pneumoniae specimen 2489
Penicillin “intermediate” (MIC 0.25 – 0.5 mg/L)
Site of infection unspecified
• Breakpoints for isolates other than meningitis
EUCAST S ≤0.06 R >2 mg/L
CLSI (parenteral) S ≤2 R ≥8 mg/L
CLSI (oral) S ≤0.06 R ≥2 mg/L
• Meningitis isolate
EUCAST S ≤0.06 R >0.06 mg/L
CLSI S ≤0.06 R ≥0.12 mg/L
Guideline n %S %I %R
EUCAST 563 17.4 75.5 7.1
CLSI 116 46.5 45.7 7.8

26. Streptococcus pneumoniae specimen 2489
Penicillin MIC 0.25 – 0.5 mg/L
• Pneumonia isolate
With EUCAST breakpoints for higher doses used in
pneumonia, and CLSI parenteral breakpoints for non-
meningitis isolates, expected result “Susceptible”
Guideline n %S %I %R
EUCAST 627 49.9 47.2 2.9
CLSI 156 86.5 13.5 0

27. Streptococcus pneumoniae specimen 2489
Penicillin MIC 0.25 – 0.5 mg/L
• Meningitis isolate
EUCAST S ≤0.06 R >0.06 mg/L
CLSI S ≤0.06 R ≥0.12 mg/L
Guideline n %S %I %R
EUCAST 625 3.7 2.4 93.9
CLSI 156 3.8 1.3 94.9

28. Streptococcus pneumoniae specimen 2489
Norfloxacin screen
EUCAST susceptible, CLSI no screening test
Guideline n %S %I %R
EUCAST 265 88.7 0 11.3
CLSI 24 83.3 0 16.7

29. Enterococcus faecium specimen 2490
High-level gentamicin resistant
Antimicrobial agent
Reference
MIC (mg/L)
EUCAST CLSI
Ampicillin 32-64 R R
Amoxicillin 32 R R
Teicoplanin 1 S S
Vancomycin 1 S S
High-level gentamicin
resistance
≥512 HLGR HLGR

30. 0
20
40
60
80
100
%Concordance
Antimicrobial agent
Enterococcus faecium specimen 2490

31. Enterococcus faecium specimen 2490
High-level gentamicin resistance positive
MIC ≥512 mg/L, EUCAST HLGR >128 mg/L, CLSI >512 mg/L
• Differences between guidelines
– EUCAST-based 92.7% positive, 7.3% negative
– CLSI 82.6% positive, 17.4% negative
• Differences between methods
– Disk 88.2% HLGR-positive
– Automated 92.2% HLGR positive
• Reasons for incorrect reports of HLGR-negative?
– Unstable resistance? Unlikely
– Misunderstanding of report form?

32. Acinetobacter baumannii specimen 2491
(GES-2 carbapenemase)
Antimicrobial agent Reference MIC (mg/L) EUCAST CLSI
Amikacin ≥128 R R
Gentamicin 32-64 R R
Tobramycin 32 R R
Ciprofloxacin 64 R R
Colistin 0.5-1 S S
Imipenem 32-64 R R
Meropenem 64-≥128 R R
Doripenem R R

33. 0
20
40
60
80
100
%Condordance
Antimicrobial agent
Acinetobacter baumannii
specimen 2491

34. Acinetobacter baumannii specimen 2491
Aminoglycoside resistant
Non-resistant reports more common with CLSI breakpoints:
Gentamicin (MIC 32-64 mg/L)
Tobramycin (MIC 32-64 mg/L)
Amikacin (MIC ≥128 mg/L)
Guideline S (mg/L) R (mg/L n %S %I %R
EUCAST ≤4 >4 640 5.6 0.5 93.9
CLSI ≤4 ≥16 162 8.0 37.7 54.3
Guideline S (mg/L) R (mg/L n %S %I %R
EUCAST ≤4 >4 544 6.4 0.3 93.3
CLSI ≤4 ≥16 131 16.0 29.8 54.2
Guideline S (mg/L) R (mg/L n %S %I %R
EUCAST ≤8 >16 549 0.5 9.1 90.4
CLSI ≤16 ≥64 146 8.9 10.3 80.8

35. Acinetobacter baumannii specimen 2491
Aminoglycoside resistant
Non-resistant reports more common with automated methods
than with disk diffusion:
Gentamicin
EUCAST
CLSI
Guideline n %S %I %R
Disk diffusion 259 2.7 0.3 99.9
Automated 322 7.8 0.6 91.6
Guideline n %S %I %R
Disk diffusion 54 3.7 25.9 70.4
Automated 100 10.0 46.0 44.0

36. Acinetobacter baumannii specimen 2491
Aminoglycoside resistant
Non-resistant reports more common with automated methods
than with disk diffusion:
Tobramycin
EUCAST
CLSI
Guideline n %S %I %R
Disk diffusion 221 3.2 0 96.8
Automated 272 9.6 0.7 89.7
Guideline n %S %I %R
Disk diffusion 46 6.5 17.4 77.1
Automated 80 21.2 38.8 40.0

37. Acinetobacter baumannii specimen 2491
Aminoglycoside resistant
Non-resistant reports more common with automated methods
than with disk diffusion:
Amikacin
EUCAST
CLSI
Guideline n %S %I %R
Disk diffusion 246 0.8 2.0 97.2
Automated 249 0.4 17.3 82.3
Guideline n %S %I %R
Disk diffusion 55 3.6 7.2 89.9
Automated 84 13.1 13.1 73.8

38. Conclusions 2014
• Performance good for most organism-
agent combinations
• Discrepancies more common when:
– Susceptibility borderline
– Critical differences between guidelines
– Failure to follow breakpoint guidelines
– Guidelines permit variable reporting
– (Failure to follow method guidelines)

39. Many thanks to all laboratories
and national distributors
UK NEQAS