Evaluation of current methods for detection of staphylococci with reduced susceptibility to glycopeptides

Timothy R Walsh; A Bolmström; A Qwärnström; P Ho; M Wootton; R A Howe; A P MacGowan; D Diekema

doi:10.1128/JCM.39.7.2439-2444.2001

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Evaluation of current methods for detection of staphylococci with reduced susceptibility to glycopeptides

Journal article

Open access

Peer reviewed

Evaluation of current methods for detection of staphylococci with reduced susceptibility to glycopeptides

Timothy R Walsh, A Bolmström, A Qwärnström, P Ho, M Wootton, R A Howe, A P MacGowan and D Diekema

Journal of clinical microbiology, Vol.39(7), pp.2439-2444

07/2001

DOI: 10.1128/JCM.39.7.2439-2444.2001

PMCID: PMC88167

PMID: 11427551

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Abstract

The sensitivity and specificity of seven methods (agar dilution, broth microdilution, Etest at 0.5 and 2.0 McFarland (McF) inocula, two agar screening methods, and population studies [PS]) were evaluated in a double-blind study involving 284 methicillin-resistant Staphylococcus aureus (MRSA) strains and 45 Staphylococcus strains with reduced susceptibilities to vancomycin (SRSV). The results were compared to the population analysis profile-area under the curve ratio method (PAP-AUC ratio compared to that of Mu3) as described by Wootton et al. The agar screening method using brain heart infusion agar (6 microg of vancomycin per ml) gave a sensitivity of 22% and a specificity of 97%. A similar method using Mueller-Hinton agar (5 microg of vancomycin per ml) gave a sensitivity of 20% and a specificity of 99%. The PS method detected 34 false positives (12%) and gave a sensitivity of 71% and a specificity of 88%. Etest using 0.5 and 2.0 McF inocula gave sensitivities and specificities of 82 and 93% and of 96 and 97%, respectively. The best Etest interpretative criteria for the 2.0 McF inoculum was > or =8 mg of vancomycin per liter and > or =8 microg teicoplanin per ml or > or =12 microg of teicoplanin per ml. The direct colony suspension inoculum for this method was found to be equally accurate in detecting (hetero-)glycopeptide-intermediate S. aureus compared to the overnight broth inoculum preparation method. Agar dilution and broth microdilution using the NCCLS breakpoint criteria for vancomycin gave sensitivities and specificities of 20 and 100% and of 11 and 100%, respectively. Using the Etest with a 2.0 McF inoculum, six different media were assessed against a selection of SRSV (n = 48) and MRSA (n = 12). Brain heart infusion agar yielded the highest sensitivity and specificity values: 88 and 88%, respectively.

Microbial Sensitivity Tests - standards

Double-Blind Method

Staphylococcus - isolation & purification

Humans

Sensitivity and Specificity

Vancomycin - pharmacology

Vancomycin Resistance

Staphylococcus - drug effects

Anti-Bacterial Agents - pharmacology

Methicillin Resistance

Staphylococcus aureus - drug effects

Microbial Sensitivity Tests - methods

Details

Title: Subtitle: Evaluation of current methods for detection of staphylococci with reduced susceptibility to glycopeptides
Creators: Timothy R Walsh - University of Bristol
A Bolmström
A Qwärnström
P Ho
M Wootton
R A Howe
A P MacGowan
D Diekema
Resource Type: Journal article
Publication Details: Journal of clinical microbiology, Vol.39(7), pp.2439-2444
DOI: 10.1128/JCM.39.7.2439-2444.2001
PMID: 11427551
PMCID: PMC88167
NLM abbreviation: J Clin Microbiol
ISSN: 0095-1137
eISSN: 1098-660X
Publisher: United States
Language: English
Date published: 07/2001
Academic Unit: Infectious Diseases; Pathology; Internal Medicine
Record Identifier: 9983986370802771

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