Intra- and interlaboratory performances of two commercial antimicrobial susceptibility testing methods for bifidobacteria and nonenterococcal lactic acid bacteria

Geert Huys (Corresponding Author), Klaas D'Haene, Marco Cnockaert, Lorenzo Tosi, Morten Danielsen, Ana Belén Flórez, Jaana Mättö, Lars Axelsson, Jenni Korhonen, Sigrid Mayrhofer, Maria Egervärn, Mauro Giacomini, Peter Vandamme

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Abstract

In a small-scale harmonization study involving nine laboratories in eight European countries, the intra- and interlaboratory performances of two commercially available systems, i.e., the VetMIC microplate system and Etest, for antimicrobial susceptibility testing of nonenterococcal lactic acid bacteria (NELAB) and bifidobacteria were analyzed. In addition, one laboratory also performed standard broth microdilution as a reference method. MICs of tetracycline, erythromycin, ampicillin, gentamicin, clindamycin, and streptomycin for the type strains of 25 species of NELAB and bifidobacteria and MICs of vancomycin for a selection of relevant taxa were determined. The previously described lactic acid bacterium susceptibility test medium (LSM) and related mixed-medium formulations, all including Iso-Sensitest broth as a basic component, were used as test media. The overall agreement of median MIC ranges ± 1 log2 dilution determined by the VetMIC and Etest methods with the median MICs determined by the reference method was very good for tetracycline, ampicillin, and streptomycin (92.3 to 100%) but low for erythromycin (19.5 to 30.7%) and clindamycin (50.0 to 80.8%). There was a consensus among the participating laboratories that VetMIC was preferred over Etest because of its lower cost, better growth support, and more uniform criteria for MIC end point reading. With the range for acceptable intralaboratory reproducibility being defined as the median MIC ± 1 log2 dilution, VetMIC results (with 69.2% of all data sets in the acceptable range) were shown to display greater reproducibility than Etest results (with 58.8% of all data sets in the acceptable range). Also at the interlaboratory level, the proportion of MIC values obtained with VetMIC that belonged to the complete agreement category (60.0%) was higher than the proportion of such values obtained with Etest (47.0%), which indicates a higher degree of interlaboratory reproducibility for the former method. Apart from some agent-specific effects, the majority of VetMIC and Etest replicate data sets were situated within a 1- to 2-log2 dilution range, suggesting that the two methods can be considered to be equivalent for recognizing resistance phenotypes. This multicenter study has further validated the standard use of LSM and related mixed-medium formulations with commercially available systems and formed the basis for the ongoing development of the ISO 10932/IDF 223 standard for susceptibility testing of NELAB and bifidobacteria.
Original languageEnglish
Pages (from-to)2567-2574
JournalAntimicrobial Agents and Chemotherapy
Volume54
Issue number6
DOIs
Publication statusPublished - 2010
MoE publication typeA1 Journal article-refereed

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Disk Diffusion Antimicrobial Tests
Bifidobacterium
Lactic Acid
Bacteria
Clindamycin
Streptomycin
Erythromycin
Ampicillin
Tetracycline
Vancomycin
Gentamicins
Reproducibility of Results
Multicenter Studies
Reading
Phenotype
Costs and Cost Analysis
Growth

Cite this

Huys, Geert ; D'Haene, Klaas ; Cnockaert, Marco ; Tosi, Lorenzo ; Danielsen, Morten ; Belén Flórez, Ana ; Mättö, Jaana ; Axelsson, Lars ; Korhonen, Jenni ; Mayrhofer, Sigrid ; Egervärn, Maria ; Giacomini, Mauro ; Vandamme, Peter. / Intra- and interlaboratory performances of two commercial antimicrobial susceptibility testing methods for bifidobacteria and nonenterococcal lactic acid bacteria. In: Antimicrobial Agents and Chemotherapy. 2010 ; Vol. 54, No. 6. pp. 2567-2574.
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abstract = "In a small-scale harmonization study involving nine laboratories in eight European countries, the intra- and interlaboratory performances of two commercially available systems, i.e., the VetMIC microplate system and Etest, for antimicrobial susceptibility testing of nonenterococcal lactic acid bacteria (NELAB) and bifidobacteria were analyzed. In addition, one laboratory also performed standard broth microdilution as a reference method. MICs of tetracycline, erythromycin, ampicillin, gentamicin, clindamycin, and streptomycin for the type strains of 25 species of NELAB and bifidobacteria and MICs of vancomycin for a selection of relevant taxa were determined. The previously described lactic acid bacterium susceptibility test medium (LSM) and related mixed-medium formulations, all including Iso-Sensitest broth as a basic component, were used as test media. The overall agreement of median MIC ranges ± 1 log2 dilution determined by the VetMIC and Etest methods with the median MICs determined by the reference method was very good for tetracycline, ampicillin, and streptomycin (92.3 to 100{\%}) but low for erythromycin (19.5 to 30.7{\%}) and clindamycin (50.0 to 80.8{\%}). There was a consensus among the participating laboratories that VetMIC was preferred over Etest because of its lower cost, better growth support, and more uniform criteria for MIC end point reading. With the range for acceptable intralaboratory reproducibility being defined as the median MIC ± 1 log2 dilution, VetMIC results (with 69.2{\%} of all data sets in the acceptable range) were shown to display greater reproducibility than Etest results (with 58.8{\%} of all data sets in the acceptable range). Also at the interlaboratory level, the proportion of MIC values obtained with VetMIC that belonged to the complete agreement category (60.0{\%}) was higher than the proportion of such values obtained with Etest (47.0{\%}), which indicates a higher degree of interlaboratory reproducibility for the former method. Apart from some agent-specific effects, the majority of VetMIC and Etest replicate data sets were situated within a 1- to 2-log2 dilution range, suggesting that the two methods can be considered to be equivalent for recognizing resistance phenotypes. This multicenter study has further validated the standard use of LSM and related mixed-medium formulations with commercially available systems and formed the basis for the ongoing development of the ISO 10932/IDF 223 standard for susceptibility testing of NELAB and bifidobacteria.",
author = "Geert Huys and Klaas D'Haene and Marco Cnockaert and Lorenzo Tosi and Morten Danielsen and {Bel{\'e}n Fl{\'o}rez}, Ana and Jaana M{\"a}tt{\"o} and Lars Axelsson and Jenni Korhonen and Sigrid Mayrhofer and Maria Egerv{\"a}rn and Mauro Giacomini and Peter Vandamme",
year = "2010",
doi = "10.1128/AAC.00407-10",
language = "English",
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pages = "2567--2574",
journal = "Antimicrobial Agents and Chemotherapy",
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Huys, G, D'Haene, K, Cnockaert, M, Tosi, L, Danielsen, M, Belén Flórez, A, Mättö, J, Axelsson, L, Korhonen, J, Mayrhofer, S, Egervärn, M, Giacomini, M & Vandamme, P 2010, 'Intra- and interlaboratory performances of two commercial antimicrobial susceptibility testing methods for bifidobacteria and nonenterococcal lactic acid bacteria', Antimicrobial Agents and Chemotherapy, vol. 54, no. 6, pp. 2567-2574. https://doi.org/10.1128/AAC.00407-10

Intra- and interlaboratory performances of two commercial antimicrobial susceptibility testing methods for bifidobacteria and nonenterococcal lactic acid bacteria. / Huys, Geert (Corresponding Author); D'Haene, Klaas; Cnockaert, Marco; Tosi, Lorenzo; Danielsen, Morten; Belén Flórez, Ana; Mättö, Jaana; Axelsson, Lars; Korhonen, Jenni; Mayrhofer, Sigrid; Egervärn, Maria; Giacomini, Mauro; Vandamme, Peter.

In: Antimicrobial Agents and Chemotherapy, Vol. 54, No. 6, 2010, p. 2567-2574.

Research output: Contribution to journalArticleScientificpeer-review

TY - JOUR

T1 - Intra- and interlaboratory performances of two commercial antimicrobial susceptibility testing methods for bifidobacteria and nonenterococcal lactic acid bacteria

AU - Huys, Geert

AU - D'Haene, Klaas

AU - Cnockaert, Marco

AU - Tosi, Lorenzo

AU - Danielsen, Morten

AU - Belén Flórez, Ana

AU - Mättö, Jaana

AU - Axelsson, Lars

AU - Korhonen, Jenni

AU - Mayrhofer, Sigrid

AU - Egervärn, Maria

AU - Giacomini, Mauro

AU - Vandamme, Peter

PY - 2010

Y1 - 2010

N2 - In a small-scale harmonization study involving nine laboratories in eight European countries, the intra- and interlaboratory performances of two commercially available systems, i.e., the VetMIC microplate system and Etest, for antimicrobial susceptibility testing of nonenterococcal lactic acid bacteria (NELAB) and bifidobacteria were analyzed. In addition, one laboratory also performed standard broth microdilution as a reference method. MICs of tetracycline, erythromycin, ampicillin, gentamicin, clindamycin, and streptomycin for the type strains of 25 species of NELAB and bifidobacteria and MICs of vancomycin for a selection of relevant taxa were determined. The previously described lactic acid bacterium susceptibility test medium (LSM) and related mixed-medium formulations, all including Iso-Sensitest broth as a basic component, were used as test media. The overall agreement of median MIC ranges ± 1 log2 dilution determined by the VetMIC and Etest methods with the median MICs determined by the reference method was very good for tetracycline, ampicillin, and streptomycin (92.3 to 100%) but low for erythromycin (19.5 to 30.7%) and clindamycin (50.0 to 80.8%). There was a consensus among the participating laboratories that VetMIC was preferred over Etest because of its lower cost, better growth support, and more uniform criteria for MIC end point reading. With the range for acceptable intralaboratory reproducibility being defined as the median MIC ± 1 log2 dilution, VetMIC results (with 69.2% of all data sets in the acceptable range) were shown to display greater reproducibility than Etest results (with 58.8% of all data sets in the acceptable range). Also at the interlaboratory level, the proportion of MIC values obtained with VetMIC that belonged to the complete agreement category (60.0%) was higher than the proportion of such values obtained with Etest (47.0%), which indicates a higher degree of interlaboratory reproducibility for the former method. Apart from some agent-specific effects, the majority of VetMIC and Etest replicate data sets were situated within a 1- to 2-log2 dilution range, suggesting that the two methods can be considered to be equivalent for recognizing resistance phenotypes. This multicenter study has further validated the standard use of LSM and related mixed-medium formulations with commercially available systems and formed the basis for the ongoing development of the ISO 10932/IDF 223 standard for susceptibility testing of NELAB and bifidobacteria.

AB - In a small-scale harmonization study involving nine laboratories in eight European countries, the intra- and interlaboratory performances of two commercially available systems, i.e., the VetMIC microplate system and Etest, for antimicrobial susceptibility testing of nonenterococcal lactic acid bacteria (NELAB) and bifidobacteria were analyzed. In addition, one laboratory also performed standard broth microdilution as a reference method. MICs of tetracycline, erythromycin, ampicillin, gentamicin, clindamycin, and streptomycin for the type strains of 25 species of NELAB and bifidobacteria and MICs of vancomycin for a selection of relevant taxa were determined. The previously described lactic acid bacterium susceptibility test medium (LSM) and related mixed-medium formulations, all including Iso-Sensitest broth as a basic component, were used as test media. The overall agreement of median MIC ranges ± 1 log2 dilution determined by the VetMIC and Etest methods with the median MICs determined by the reference method was very good for tetracycline, ampicillin, and streptomycin (92.3 to 100%) but low for erythromycin (19.5 to 30.7%) and clindamycin (50.0 to 80.8%). There was a consensus among the participating laboratories that VetMIC was preferred over Etest because of its lower cost, better growth support, and more uniform criteria for MIC end point reading. With the range for acceptable intralaboratory reproducibility being defined as the median MIC ± 1 log2 dilution, VetMIC results (with 69.2% of all data sets in the acceptable range) were shown to display greater reproducibility than Etest results (with 58.8% of all data sets in the acceptable range). Also at the interlaboratory level, the proportion of MIC values obtained with VetMIC that belonged to the complete agreement category (60.0%) was higher than the proportion of such values obtained with Etest (47.0%), which indicates a higher degree of interlaboratory reproducibility for the former method. Apart from some agent-specific effects, the majority of VetMIC and Etest replicate data sets were situated within a 1- to 2-log2 dilution range, suggesting that the two methods can be considered to be equivalent for recognizing resistance phenotypes. This multicenter study has further validated the standard use of LSM and related mixed-medium formulations with commercially available systems and formed the basis for the ongoing development of the ISO 10932/IDF 223 standard for susceptibility testing of NELAB and bifidobacteria.

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DO - 10.1128/AAC.00407-10

M3 - Article

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EP - 2574

JO - Antimicrobial Agents and Chemotherapy

JF - Antimicrobial Agents and Chemotherapy

SN - 0066-4804

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