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Tentative breakpoints and areas of technical uncertainty for early reading automated disc diffusion for Enterobacterales


Mancini, Stefano; Röthlin, Kim; Bodendoerfer, Elias; Herren, Sebastian; Kolesnik-Goldmann, Natalia; Courvalin, Patrice; Zbinden, Reinhard; Böttger, Erik C (2020). Tentative breakpoints and areas of technical uncertainty for early reading automated disc diffusion for Enterobacterales. Journal of Antimicrobial Chemotherapy, 75(6):1495-1505.

Abstract

BACKGROUND

Disc diffusion is a reliable, accurate and cost-efficient procedure for antimicrobial susceptibility testing (AST) but requires long (18-24 h) incubation times. Reading of disc diffusion after short incubation times (6-8 h) by automated systems is feasible but should be categorized with time-adapted breakpoints to reduce errors.

OBJECTIVES

This study systematically compared early readings (6 and 8 h) of disc diffusion using an automated system with that of the standard 18 h EUCAST method. Time-adapted tentative breakpoints were proposed to discriminate susceptible from resistant isolates and areas of technical uncertainty were defined to minimize the risk of errors.

METHODS

A total of 1106 Enterobacterales isolates with a wide variety of resistance mechanisms and resistance profiles were included. All isolates were analysed for susceptibility to amoxicillin/clavulanic acid, ceftriaxone, cefepime, meropenem, ciprofloxacin and gentamicin using the automated WASPLabTM system. Part of the collection (515 isolates) was also analysed for susceptibility to an additional 10 antibiotics.

RESULTS

Separation between WT and non-WT populations was poorer at early incubation times than following standard incubation. Editing of rapid automated AST results after 6 and 8 h incubation with time-adapted breakpoints resulted in 84.0% and 88.5% interpretable results with assignment to the resistant or susceptible category. Major error and very major error rates for the 6 h readings were only 0.4% and 0.3%, virtually identical to those of 18 h AST reading.

CONCLUSIONS

Time-adapted clinical breakpoints in disc diffusion testing for Enterobacterales allow for accurate automated AST interpretation after shortened incubation times for a large number of antibiotics, with the additional possibility of subsequent confirmation after 18 h incubation.

Abstract

BACKGROUND

Disc diffusion is a reliable, accurate and cost-efficient procedure for antimicrobial susceptibility testing (AST) but requires long (18-24 h) incubation times. Reading of disc diffusion after short incubation times (6-8 h) by automated systems is feasible but should be categorized with time-adapted breakpoints to reduce errors.

OBJECTIVES

This study systematically compared early readings (6 and 8 h) of disc diffusion using an automated system with that of the standard 18 h EUCAST method. Time-adapted tentative breakpoints were proposed to discriminate susceptible from resistant isolates and areas of technical uncertainty were defined to minimize the risk of errors.

METHODS

A total of 1106 Enterobacterales isolates with a wide variety of resistance mechanisms and resistance profiles were included. All isolates were analysed for susceptibility to amoxicillin/clavulanic acid, ceftriaxone, cefepime, meropenem, ciprofloxacin and gentamicin using the automated WASPLabTM system. Part of the collection (515 isolates) was also analysed for susceptibility to an additional 10 antibiotics.

RESULTS

Separation between WT and non-WT populations was poorer at early incubation times than following standard incubation. Editing of rapid automated AST results after 6 and 8 h incubation with time-adapted breakpoints resulted in 84.0% and 88.5% interpretable results with assignment to the resistant or susceptible category. Major error and very major error rates for the 6 h readings were only 0.4% and 0.3%, virtually identical to those of 18 h AST reading.

CONCLUSIONS

Time-adapted clinical breakpoints in disc diffusion testing for Enterobacterales allow for accurate automated AST interpretation after shortened incubation times for a large number of antibiotics, with the additional possibility of subsequent confirmation after 18 h incubation.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:04 Faculty of Medicine > Institute of Medical Microbiology
Dewey Decimal Classification:570 Life sciences; biology
610 Medicine & health
Scopus Subject Areas:Life Sciences > Pharmacology
Health Sciences > Microbiology (medical)
Health Sciences > Infectious Diseases
Health Sciences > Pharmacology (medical)
Language:English
Date:1 June 2020
Deposited On:19 Jan 2021 12:46
Last Modified:08 Jun 2024 03:40
Publisher:Oxford University Press
ISSN:0305-7453
OA Status:Closed
Free access at:Publisher DOI. An embargo period may apply.
Publisher DOI:https://doi.org/10.1093/jac/dkaa051
PubMed ID:32155259
Full text not available from this repository.