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BSAC Standardized Disc Susceptibility Testing Method - User Group Meeting. Cardiff, 13 May 2010

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. 1 Year B.V. (before Vitek....). Previously....

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BSAC Standardized Disc Susceptibility Testing Method - User Group Meeting. Cardiff, 13 May 2010

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  1. 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. 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

  3. 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)

  4. 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

  5. Sensitivity testing 1 Year AV • Gram negatives • UTI • Use Chromogenic Media • E.coli – treated as E.coli, VitekSens • Coliform group – VitekSens 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

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

  7. 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!

  8. Issues – Antibiotic Concentrations • Rifampicin • Card tests at 0.25,0.5 and 2mg/L • Calling range 0.25-4mg/L • EUCAST/BSAC ‘S’ cut off = 0.06mg/L ‘I‘= 0.12-0.5 ‘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

  9. Issues – Antibiotic Concentrations • Mupirocin • Card tests 1mg/L • Calling range 2-8mg/L! BSAC ranges S= ≤4 I= 8-256 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.....

  10. 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

  11. Detection of resistance • Detection of AmpC

  12. 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

  13. 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

  14. 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)

  15. Solution ? • *BSAC Cefpodoxime ‘S’ cut off 1mg/L

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

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

  18. 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

  19. 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?

  20. More areas to investigate?

  21. 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?

  22. 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

  23. 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.

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