NordicAST VRE study 2012 Comparing phenotypic detection methods

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1 NordicAST VRE study 2012 Comparing phenotypic detection methods Kristin Hegstad Reference Centre for Detection of Antimicrobial Resistance, Department of Microbiology and Infection Control, University Hospital of North-Norway Research group for Host-Microbe Interactions, Faculty of Health Sciences, University of Tromsø

2 Acquired vancomycin resistance in enterococci vana, B, D, E, G, L, M and vann vanb resistant to vancomycin (MIC mg/l) susceptible to teicoplanin (MIC 2 mg/l) EUCAST MIC clinical breakpoints glycopeptides Enterococcus spp. vancomycin R > 4 mg/l teicoplanin R > 2 mg/l

3 Screening av kliniske enterokokkisolater for vankomycinresistens Norge spotinokulering 6 mg/l vankomycin BHI-agar Sverige EUCAST disk diffusjon vanb E. faecium outbreak strain from Västerås

4 vanb cluster spread Can be part of successful hospital adapted clones May transfer as part of large chromosomal elements or plasmids Predominant subtype vanb2 integral part of; Bjørkeng et al., APMIS 119:247-58; Hegstad et al., 2010 Clin Microbiol Infect 16: ; Hegstad et al., unpublished; Lopez et al., Clin Microbiol Infect 15:586-8;

5 vanb cluster can be part of transferable plasmids containing addiction systems Fig. 2 Hegstad 2010 Clin Microbiol Infect 16: Bjørkeng 2011 APMIS 119: Hegstad et al. Unpublished results

6 VRE Europe 2011 E. faecalis E. faecium EARS net database

7 VRE infection and colonisation in Norway Country of infection Norway Unknown Abroad Total Outbreak with low vancomycin MIC vanb E. faecium

8 Blinded material (n=30) Species van genotype Vancomycin Etest MIC range mg/l No. of strains E. faecalis B1 / B / 4 3 / 1 E. faecalis E 16 1 E. faecalis G 16 1 E. faecalis ATCC E. faecalis ATCC B 16 3 E. faecium B1 / B2 >256/8- >256 1 / 17 Included outbreak strains with low-level vancomycin resistance from Bergen (1996), Örebro ( ), Huddinge (2007) and Västerås (2008) 24 PFGE types 5 MLST types among 9 typed strains

9 Participation and methods 34 Scandinavian labs participated 13 Norwegian 12 Swedish 9 Danish Methods No. of labs Disk diffusion (6mm disks) 30 (32) Disk diffusion (Neosensitabs) 3 BHI agar screen vanco 6 mg/l 21 VRE Chrom Agar 14 Vitek 7 Phoenix 1

10 Results automated systems Method (n=no. of labs) No. very major errors No. major errors Phoenix (n=1) 4 (15%) 0 (0%) Vitek (n=7) 25 (13%) 0 (0%) - Card AST-P586 (n=2) 17 (63%) - Card AST-P594 (n=1) 3 (11%) - Card AST-P592 (n=3) 5 (6,2%) Very major error = classified as S when containing van genotype Major error= classified as R when containing no van genotype

11 Results disk diffusion Method (n=no. of labs) No. very major errors No. major errors 6 mm disks (n=32) 52 (6,4%) 2 (2,2%) - BBL MH II (n=11) 36 (12%) 2 (6,1%) - Oxoid MH (n=18) 14 (2,9%) - Merck MH (n=2) 2 (3,7%) - BioRad MH (n=1) 0 (0%) Neosensitabs (n=3) 11 (14 %) 0 (0%) - Biomerieux MH II (n=2) 5 (9,3%) - BBL MH II (n=1) 6 (22%) If zone edge was fuzzy or colonies grew within the zone, the sample was considered R even though the zone size suggested S

12 Results agar screen Method (n= no. of labs) Very major error Major error BHI vanco 6 (n=21) 47 (8,3%) 4 (6,3%) - BHI Difco (n=8) 9 (4,2%) - BHI Oxoid (n=5) 15 (11%) - BHI Scharlau (n=1) 1 (3,7%) - BHI Acumedia (n=1) 1 (3,7%) - BHI BD (n=6) 21 (13%) 4 (22%) VRE Chrom Agar (n=14) 8 (2,1%) 6 (14%) - CHROMagar (n=5) 4 (3,0%) 3 (20%) - BioMerieux (n=9) 4 (1,6%) 3 (11%) Very major error = No growth when containing van genotype Major error = Growth when containing no van genotype

13 Etest MIC distribution of errors % errors of samples > 256 MIC in mg/l Automated methods (n=8) Disk diffusion (n=34) Agarscreen (n=35)

14 Resistant strains that were often classified as S Strain no. Species PFGE type van genotype Vanco MIC mg/l Etest/ microbroth dilution Range mm Zones No. of R classified as S Disk diffusion (n=33) Agar screen (n=35) Automated methods (n=8) 4 E. faecium I B2 8 / E. faecium II B2 8 / E. faecalis III B1 8 / E. faecium IV B2 8 / E. faecalis V G 16 / E. faecium VI B2 16* / E. faecium VI B2 16* / E. faecium VI B2 16* / E. faecalis VII B2 4 / * Outbreak strain from Västerås showed double zone by Etest

15 Middle and median numbers per lab Method (n=no. of labs) No. very major errors/lab Number No. major errors/lab Middle Median Middle Median Vitek (n=7) 3, BHI vanco 6 (n=21) 2,2 2,0 0,19 0 VRE Chrom Agar (n=14) 0,5 0 0,36 0 Disk diffusion 6mm (n=30) 1,7 1 0,067 0 Neosensitabs (n=3) 3,

16 Lowest and highest numbers per lab Method Number No. very major errors/lab No. major errors/lab Lowest Highest Lowest Highest Vitek BHI vanco VRE Chrom Agar Disk diffusion 6mm Neosensitabs

17 Comparing results by countries Method Country (no. of labs) Very major errors in % Disk diffusion 6 mm disks BHI vanco 6 VRE Chrom agar Major errors in % Sweden (14) 1,3 0 Norway (13) 10 2,6 Denmark (5) 8,9 6,7 Sweden (1) 3,7 0 Norway (13) 6,8 0 Denmark (7) Sweden (7) 1,6 14 Norway (6) 3,1 17 Denmark (1) 0 0

18 Comparing results by media and country Method Disk diffusion 6 mm disks BHI vanco 6 VRE Chrom agar Media (no. of labs from N, S or DK) Very major errors in % Major errors in % BBL MH II (7N/1S/3DK) 12 (13/0/14) 6,1 (5/0/11) Oxoid MH (4N/12S/2DK) 2,9 (7/2/2) 0 Merck MH (2N) 3,7 0 BioRad MH (1S) 0 0 BHI Difco (7N/1DK) 4,2 (4/4) 0 BHI Oxoid (5N) 11 0 BHI Montebello (1N) 3,7 0 BHI Acumedia (1S) 3,7 0 BHI BD (6DK) CHROMagar (5N) 3,0 20 BioMerieux (1N/7S/1DK) 1,9 (4/2/0) 13 (0/14/0)

19 Summary Method No. very major errors No. major errors Vitek 25/189 (13%) 0/21 (0%) Phoenix 4/27 (15%) 0/3 (0%) BHI vanco 6 47/567 (8,3%) 4/63 (6,3%) VRE Chrom Agar 8/378 (2,1%) 6/42 (14%) Disk diffusion 6mm 52/864 (6,0%) 2/96 (2,1%) Neosensitabs 11/81 (14 %) 0/6 (0%)

20 Noen tanker vanb kan være vanskelig å fange opp med tilgjengelige metoder Ingen av de testede metodene var feilfrie Viktig med metoder som fungerer i rutinelab Metoder med lite rom for tvil om tolkning er lettere å forholde seg til i rutinehverdagen Gode nok positive kontrollstammer for fenotypisk testing av lavgradig vankomycinresistens? Vankomycin MIC-verdi (8 mg/l) som utfordrer testbetingelser ATCC51299 anbefalt pos kontroll MIC 16-64! Prosjekter som dette brukes spesialisert personale eller leses de av som vanlige rutineprøver

21 Stor takk til deltakerlaboratoriene Aalborg Sygehus Aarhus Universitetshospital Akershus Universitetssykehus Aleris Medilab Central Hospital Växsjö Centralsjukhuset Karlstad Førde Sentralsjukehus Hallands Sjukhus Halmstad Haukeland Universitetssykehus Herlev Hospital Hillerød Hospital Hvidovre Hospital Länssjukhuset i Kalmar Karolinska Universitetssjukhuset Huddinge Karolinska Universitetssjukhuset Solna Linköping Universitetssjukhuset Molde Sykehus Nordlandssykehuset Bodø Odense Universitetshospital Rikshospitalet Oslo Sahlgrenska Universitetssjukhuset Skånes Universitetssjukhus Lund Skånes Universitetssjukhus Malmö Slagelse Sygehus Statens Serum Institut Stavanger Universitetssjukehus St. Olavs Hospital Sykehuset i Vestfold Sykehuset Østfold Sørlandet Sykehus Ullevål Universitetssykehus Universitetssykehuset Nord-Norge Uppsala Akademiska Sjukhuset Velje Sygehus