insert name of presentation on master slide automated systems: an overview robin a howe cardiff
TRANSCRIPT
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Insert name of presentation on Master Slide
Automated systems:an overview
Robin A HoweCardiff
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AST standards
• MIC taken as standard measure of susceptibility– Agar dilution– Broth dilution– Microbroth dilution
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• ISO standard– Broth microdiluion– Mueller-Hinton Broth– Inoculum 5x105
cfu/mL
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AST standards• MIC taken as standard measure of
susceptibility– Agar dilution– Broth dilution– Microbroth dilution
• S/I/R Breakpoints defined by BSAC/EUCAST/CLSI
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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
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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
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Identification required for interpretation of BP & expert rules
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Welsh variability in ID of Enterobacter/Klebsiella/Serratia
93.1
75.0
94.4 95.5
66.974.7
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
% A
gree
men
t
Lab 1 Lab 2 Lab 3 Lab 4 Lab 5 Total
Laboratory
Inter-laboratory ID comparisons
ID Disagree
ID Agree Genus
ID Agree
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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
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Welsh Gram negative panel
Welsh Gram positive panel
Drug RangeAmikacin 4 - 32Gentamicin 1 - 8Tobramycin 2 - 8Ampicillin 4 - 32Amoxicillin/Clav 2/1 - 32/16Cefotaxime 1 - 4Cefoxitin 1 - 4Ceftazidime 2 - 16Cefuroxime 4 - 16Cephalexin 4 - 16Ciprofloxacin 0.25 - 2Aztreonam 1 - 16Imipenem 1 - 8Meropenem 1 - 8Ertapenem 0.5 - 4Colistin 1 - 4Piperacillin/Tazo 4/4 - 32/4Trimethoprim 0.5 - 4Trimethoprim/Sulfa 0.8/15.2 - 3.2/60.8Nitrofurantoin 16 - 64Levofloxacin 0.5-2
Drug RangeGentamicin 1 - 4Penicillin 0.06 - 0.25Oxacillin 1 - 4Ampicillin 2 - 16Amoxicillin/Clav 1/0.5 - 16/8Levofloxacin 0.5 - 2Ciprofloxacin 0.5 - 2Cefoxitin 2 - 8Linezolid 2 - 8Erythromycin 0.25 - 1Clindamycin 0.25 - 1Daptomycin 1 - 16Chloramphenicol 1 - 16Nitrofurantoin 16 - 64Fusidic Acid 1 - 8Rifampin 0.25 - 1Minocycline 0.5 - 2Mupirocin 1 - 4Mupirocin - HL 256Teicoplanin 1 - 16Tetracycline 0.5 - 2Trimethoprim 0.5 - 4Vancomycin 1 - 16GM-Syn 500ST-Syn 1000
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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
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Available systems
• MicroScan WalkAway
• Biomerieux Vitek 2
• BD Phoenix
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MicroScan
• 96 well plates• AST based on conventional microbroth
dilution MIC• ID currently biochemical
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Microscan• Conventional panels
• Enterobacteriaceae, gram-negative non-fermenters, staphylococci, enterococci
• Combo, MIC-only, ID-only• Rapid panels
– 2 - 2.5 hour ID (pre-formed enzymes)– AST for Gram negative organisms (MIC > 4
hrs)• Synergies plus panels
– 2 - 2.5 hour ID (pre-formed enzymes)– 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
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Microscan
• Expert rules within LabPro Alert system– Pre-loaded– customisable
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Microscan
• Expert rules within LabPro Alert system– Pre-loaded– customisable
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Vitek 2
• AST based on broth susceptibility with specific cards
• ID currently biochemical
• Growth/reactions “continuously” monitored
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Vitek 2
• ID Cards available for– Gram positives– Enterobacteriaceae– Non-Enterobacteriaceae– Neisseria/Haemophilus etc– Anaerobes– Yeasts
• AST Cards available for– Gram positive cocci– Gram negative bacilli– Yeasts
• Up to 22 antibiotics tested on each card
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TIME (hours)0 1 2 3 4 5 6 7 8 9 10 11 12 1413 1615 17 18
Raw Data
% Change
Slope
Area
SLPAR
Interpretation of Raw Data
Growth Parameters
MIC
VITEK 2 – MIC Interpretation
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Vitek 2
• Expert rules within the Advanced Expert System (AES)– Extensive
Knowledge Base • >20,000 MIC
distributions• >2,500
Phenotypes• >200 Resistance
Mechanisms
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Vitek 2
CARD Type Time to Result
GN ID 2 to 10 hours
GP ID 2 to 8 hours
NH ID 6 hours
ANC ID 6 hours
YST ID 18 hours
GN AST 2 to 18 Hours
GP AST 2 to 18 Hours
AST-YS01 6 hours
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Phoenix
• AST based on broth susceptibility with specific cards
• ID currently biochemical
• Growth/reactions “continuously” monitored
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Phoenix
• AST only or Combo panels available for – GN (Enterobacteriaceae/
Nonfermenters)– GP (Staphylococci/
Enterococci/ Streptococci)– Streptococci ID/AST
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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
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Phoenix• Expert rules within BDXpert based
on CLSI/SFM/DIN/EUCAST rules bases
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Comparison of systems Microscan Vitek 2 Phoenix
ID available
GPOS GNEG NH
AnO2 Yeast
GPOS GNEG
NH AnO2 Yeast
GPOS GNEG
AST available GPOS GNEG
GPOS GNEG Yeast
GPOS GNEG
Reading Continuous automated
or manual Continuous automated Continuous automated
MIC Y +/- +/- Expert system Published rules Phenotypic comparison Published rules Biochemical ID Plans for integration with non-biochemical ID systems
Epidemiological software
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Performance
• ID– 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
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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
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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
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