1. Automated systems: an overview
Robin A Howe
Cardiff
Insert name of presentation on Master Slide

2. AST standards MIC taken as standard measure of susceptibility
Agar dilution
Broth dilution
Microbroth dilution

3. ISO standard Broth microdiluion Mueller-Hinton Broth
Inoculum 5x105 cfu/mL

4. AST standards MIC taken as standard measure of susceptibility
Agar dilution
Broth dilution
Microbroth dilution
S/I/R Breakpoints defined by BSAC/EUCAST/CLSI

6. AST standards MIC taken as standard measure of susceptibility
Agar dilution
Broth dilution
Microbroth dilution
S/I/R Breakpoints defined by BSAC/EUCAST/CLSI
MIC/BP supplemented by “expert rules” for clinical use

7. The rationale for automated systems
More reliable AST results
?closer to “standard”
Reduced scope for “user” error
Reproducible
Improved ID linked to AST
Embedded expert rules
Automated systems: an overview

8. Identification required for interpretation of BP & expert rules

9. Welsh variability in ID of Enterobacter/Klebsiella/Serratia

10. The rationale for automated systems
More reliable AST results
Improved ID linked to AST
Embedded expert rules
Improved speed of results
Increased number of agents tested
Automated systems: an overview

11. Welsh Gram negative panel Welsh Gram positive panel

12. The rationale for automated systems
More reliable AST results
Improved ID linked to AST
Embedded expert rules
Improved speed of results
Increased number of agents tested
Laboratory workflow
Staff skill mix
Epidemiological software
Automated systems: an overview

13. Available systems
MicroScan WalkAway
Biomerieux Vitek 2
BD Phoenix

14. MicroScan
96 well plates
AST based on conventional microbroth dilution MIC
ID currently biochemical

15. Microscan Conventional panels Rapid panels Synergies plus panels
Enterobacteriaceae, gram-negative non-fermenters, staphylococci, enterococci
Combo, MIC-only, ID-only
Rapid panels
hour ID (pre-formed enzymes)
AST for Gram negative organisms (MIC > 4 hrs)
Synergies plus panels
Broth microdilution “Read-when-ready” MIC
Resistance detection flagged in as few as 4.5 hours
All results finalized in 16/18 hours
Additional
Yeast ID, Anaerobe ID, HNID
MICroSTREP plus ® - dry format
ESβL plus ® -ESβL Confirmatory Panel
Panels read by
WalkAway® systems
autoSCAN-4
Manual

16. Microscan Expert rules within LabPro Alert system Pre-loaded
customisable

17. Microscan Expert rules within LabPro Alert system Pre-loaded
customisable

18. Vitek 2 AST based on broth susceptibility with specific cards
ID currently biochemical
Growth/reactions “continuously” monitored

19. Vitek 2 ID Cards available for AST Cards available for
Gram positives
Enterobacteriaceae
Non-Enterobacteriaceae
Neisseria/Haemophilus etc
Anaerobes
Yeasts
AST Cards available for
Gram positive cocci
Gram negative bacilli
Up to 22 antibiotics tested on each card

20. VITEK 2 – MIC Interpretation
Interpretation of Raw Data
Growth Parameters
MIC
Area
Raw Data
Slope
% Change
SLPAR 1 2 3 4 5 6 7 8 9 10 11 12 14 13 16 15 17 18
TIME (hours) 20

21. Vitek 2 Expert rules within the Advanced Expert System (AES)
Extensive Knowledge Base
>20,000 MIC distributions
>2,500 Phenotypes
>200 Resistance Mechanisms

22. Vitek 2 CARD Type Time to Result GN ID 2 to  10 hours GP ID
NH ID
6 hours
ANC ID
YST ID
18 hours
GN AST
2 to 18 Hours
GP AST
AST-YS01

23. Phoenix AST based on broth susceptibility with specific cards
ID currently biochemical
Growth/reactions “continuously” monitored

24. Phoenix AST only or Combo panels available for
GN (Enterobacteriaceae/ Nonfermenters)
GP (Staphylococci/ Enterococci/ Streptococci)
Streptococci ID/AST

25. Phoenix Readings for each well taken and calculated every 20 minutes
ID uses red, green, blue and UV light sources
AST measures turbidity and color change
Each well divided into pixels
Readings taken for each pixel
Entire process takes 7 minutes
Pixel data analyzed for each well
Readings for each well compared to previous reading and baseline
Well is complete when specific amount of change is not seen
Substrate/antimicrobic algorithm dependent
Instrument will post results when enough data collected

26. Phoenix
Expert rules within BDXpert based on CLSI/SFM/DIN/EUCAST rules bases

27. Comparison of systems

28. Performance ID AST Correct to genus >95% Correct to Species>90%
Difficulties with difficult organisms
Non-fermenters
Shigella etc
AST
Concordant with other methods >95%
Specific issues with specific drug-bug combinations & certain instruments
VISA/VRSA
Beta-lactams & Pseudomonas

29. Performance
ID/AST performance relies on correct ID, correct AST plus appropriate expert interpretation
Incorrect ID can lead to incorrect AST
Up to 5% errors mean that results should be examined critically

30. Conclusions Automated systems can provide
Reliable AST integrated with ID & expert rules
Improved speed of results
Caution about staff skill mix and interpretation of results
Microscan/ Vitek 2 /Phoenix have similar performance overall
Results should be examined critically