1. Vitek 2 – A User Experience.
BSAC Standardized Disc Susceptibility Testing Method - User Group Meeting. Cardiff, 13 May 2010
Vitek 2 – A User Experience.
Nathan Reading
Senior Biomedical Scientist
Sandwell and West Birmingham Hospitals NHS Trust

2. Our Department Covers 3 Hospital Sites
Totalling 1000 beds
Serves approx 0.6 million people
Specialist Supra-Regional Eye Hospital
Birmingham Treatment Centre
Microbiology department is home of BSAC Standardized Method Development Centre

3. Our Department
Long term user/initial developer of BSAC Standard Method
Research interests in mechanisms of antimicrobial resistance and sensitivity testing
Approx 6 WTE’s
Implemented automated system – Vitek 2 XL June 2009

4. 1 Year B.V. (before Vitek....) Previously....
Disc susceptibilities for >90% isolates
Urines
Blood Cultures (Direct and Repeats)
Respiratory
Ocular
General – swabs etc
Agar Dilution MIC’s
All Pseudomonads
Resistant gram negatives
Ad-hoc organism/difficult infections
Gradient Tests
Difficult organisms
Adhoc testing/confirmations

5. 1 Year B.V. (before Vitek....) Staffing required.. 1 Senior BMS W.T.E.
2x BMS W.T.E.
0.5 MLA W.T.E.
Daily/Weekly Tasks
Reading Plates/Setting Up Disc Susceptibility Plates and pouring Agar Dilution Plates/Preparing Antibiotic Stocks and Dilutions/Setting up MIC plates/Reading MIC Plates.
Working Day
8am-5pm Weekday
8am-12pm Saturdays (All sensitivities bar MIC’s read, all sensitivities put up bar urinary isolates)
8am-1pm Sundays (Only Blood Culture and MRSA sensitivities setup/read)

6. Sensitivity testing 1 Year AV (after Vitek...)
1 x Senior BMS WTE
1x BMS WTE
0.6 xMLA WTE
Reduced staff overhead
Senior BMS freed to look after our organism collection
All sensitivity testing complete >90% time by 4pm
Sensitivity testing ready for release to clinician by 10-11am
We do not release same day sensitivity testing....
Do not wish to retract incorrect reports
Our working days structure currently means that cards not going onto Vitek until mid morning earliest

7. Sensitivity testing 1 Year AV
Gram negatives
UTI
Use Chromogenic Media
E.coli – treated as E.coli, Vitek Sens
Coliform group – Vitek Sens and Automated ID also
Systemic -Fermenters
Automated ID and Sensitivity Test
Non fermenters
Automated ID or Basic Manual ID
Automated Sensitivity Test
Blood Cultures
Direct disc susceptibility – in-house dilution protocol
Repeats by Vitek

8. Sensitivity testing 1 Year AV
Gram positives
Staphylococci
Vitek Sensitivity
Manual ‘traditional’ ID
API/Vitek GP Card for discrepant organisms
Enterococci
Antibiogram/API/Vitek GP card if speciation needed
Beta Haem Streptococci
Vitek (Group B) and Discs (All others)
Fastidious Organisms
Discs!

9. Issues - Flexability Card ‘make up’ will never perfect for every user
Bespoke cards can be made for individuals
For our UTI’s
No Amikacin on UTI card – only Gent
We now disc test Amikacin on Gent I/R
Aminoglycoside rules cant work properly
No Mecillinam
Our clinicians want Mecillinam on all Trim R isolates of E.coli/Kleb/Proteus can be 30% isolates!

10. Issues – Antibiotic Concentrations
Rifampicin
Card tests at 0.25,0.5 and 2mg/L
Calling range mg/L
EUCAST/BSAC ‘S’ cut off = 0.06mg/L ‘I‘= ‘R’ =>0.5
Card does not test low enough to determine S using BSAC/EUCAST breakpoints
Recent card revision did not solve this
Now need to disc test on ad-hoc basis if clinicians require result

11. Issues – Antibiotic Concentrations
Mupirocin
Card tests 1mg/L
Calling range 2-8mg/L!
BSAC ranges S= ≤4 I= R >256
Need to disc test to differentiate I from R
Mupirocin decolonisation may still work if Intermediate
Recent revision to cards did not solve this.....

12. Detection of resistance
Detection of Hyperproduction of K1 enzyme in Kleb oxytoca
No Aztreonam on UTI Card AST N144
Need to rely on Inhibitor Resistance and Cefotaxime which can be variable
Offline Synergy Test
Cefpodoxime/Cefpodoxime+Clav/Cefpodoxime+Clav+Boronic Acid
Aztreonam disc testing

13. Detection of resistance
Detection of AmpC

14. Detection of AmpC Cefoxitin Resistant 3rd Gen Ceph’s = S Check ID
Some Chromogenic agars mis-identify Citrobacter species (may have natural AmpC)
Check ESBL/Confirmation Test
Cefpodoxime/Cefpodoxime+Clav/Cefpodoxime+Clav+Boronic Acid
If negative synergy – probable impermeability/porin loss
If positive synergy with Boronic Acid/Clav/Cefpodozime = AmpC

15. Detection of Resistance
Detection of ESBL
Compared 296 urinary isolates screened with HMRZ -86 a chromogenic 3rd gen Cephalosporin
Vitek missed 11 ESBL producers out of a total of 42
Situation improved a little on software update
?algorithms changed
Still misses some low expression of ESBL

16. Solution ?
All of the missed isolates (ESBL&AmpC) reduced zone to Cefpodoxime 10ug disc
?Need a Vitek card containing Cefpodoxime
18 missed isolates E.coli/Klebsiella
10 ESBL Missed with routine card
7 AmpC Missed with routine card
1 K1 K oxytoca (included for interest)

17. Routine Method Findings
Solution ?
Isolate ID
CPD Zone/mm
Routine Method Findings
AES Findings
Cefpod
Ceftaz
Ceftriax
Escherichia coli 17
ESBL
acquired penicillinase
>8 ≤1 10
AMP C
Inconsistent 14 2
Acquired Penicillinase 15
0.5
Klebsiella pneumoniae
ACQ Penicillinase + Impermeability (Cephamycins), Impermeability (Cephamycins)
<0.25 11
amp c
Klebsiella oxytoca 18
?K1 hyper
high level natural penicillinase
<1
ESBL (ctx-m), high level natural penicillinase 21
ACQ Penicillinase 13
ampc
Acq Penicillinase
esbl 4 12
Acq penicillinase 16
*BSAC Cefpodoxime ‘S’ cut off 1mg/L

18. Solution ?
16/18 isolates all had MIC for Cefpodoxime >1mg/L (BSAC breakpoint)
Include Cefpodoxime on card?
With or without CAZ,CTX?

19. Detection of Resistance
What is this isolate?
System highlights MRSA as possible mechanism – changes Cefoxitin result from Negative to POSITIVE

20. Solution ? All isolates showing this change
PBP 2’ Latex (Oxoid/Mast)
20 minute test
If +ve therefore MRSA
If –ve need to rule out MRSA still.
Cefoxitin 10 disc on IsoSensitest
MecA PCR
Our own mini study – partially complete
20 isolates Oxacillin ‘R’ / Cefox Screen Changed to +ve
10 strains MecA negative (Internal control Nuc +ve = S.aureus)
All 10 PBP 2’ Latex Negative

21. Difficult isolates Mucoid isolates – esp Pseudomonads
Difficult to get a smooth inoculum
May give false resistance/susceptibility
Need a plan B
MIC?
Gradient Test?
Discs?

22. More areas to investigate?

23. More areas to investigate?
Vitek 2 Implentaton
New Cards
Software upgrade

24. More areas to investigate?
Vitek 2 Implentaton
Software upgrade

25. New and Emerging Phenotypes
July 2009
Our first Isolate of NDM-1 Carbapenemase in Klebsiella pneumoniae
Detected by Vitek 2
Subsequent challenge with further strains from other centres also detected as expected
Isolates with VIM,IMP and KPC isolates also detected.
Carbapenemases, the new ESBL?

26. Summary
Automated systems not panacea for solving lack of AST knowledge within laboratory.
Some users may find more questions than answers
BSAC method still required to fill in the gaps
Not just fastidious organisms
Some areas could be optimised to enhance detection of important isolates
Some cards need to be improved for UK/EUCAST breakpoints

27. Summary – the positives
Reduction of staff overhead
Improved speed of results
We at City dont make best use of all benefits of automation
Can be used to upskill knowledge of AST and mechanisms of resistance
Simple to use and well supported by the company.