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Change of antibiotic susceptibility testing guidelines from CLSI to EUCAST: influence on cumulative hospital antibiograms.

Wolfensberger A, Sax H, Weber R, Zbinden R, Kuster SP, Hombach M - PLoS ONE (2013)

Bottom Line: The majority of species/drug combinations showed no differences in susceptibility rates comparing periods A and B.These differences were still evident when comparing susceptibility rates according to the CLSI 2013 guideline with EUCAST 3.1 guideline.For P. aeruginosa and imipenem, a trend towards a lower antibiotic susceptibility rate in ICUs compared to general wards turned into a significant difference after the change to EUCAST: 87.9% vs. 79.8%, P=0.08 (CLSI 2009) and 86.3% vs. 76.8%, P=0.048 (EUCAST 1.3).

View Article: PubMed Central - PubMed

Affiliation: Division of Infectious Diseases and Hospital Epidemiology, University Hospital and University of Zurich, Zurich, Switzerland.

ABSTRACT

Objective: We studied whether the change in antibiotic susceptibility testing (AST) guidelines from CLSI to EUCAST influenced cumulative antibiograms in a tertiary care hospital in Switzerland.

Methods: Antibiotic susceptibilities of non-duplicate isolates collected within a one-year period before (period A) and after (period B) changing AST interpretation from CLSI 2009 to EUCAST 1.3 (2011) guidelines were analysed. In addition, period B isolates were reinterpreted according to the CLSI 2009, CLSI 2013 and EUCAST 3.1 (2013) guidelines.

Results: The majority of species/drug combinations showed no differences in susceptibility rates comparing periods A and B. However, in some gram-negative bacilli, decreased susceptibility rates were observed when comparing CLSI 2009 with EUCAST 1.3 within period B: Escherichia coli / cefepime, 95.8% (CLSI 2009) vs. 93.1% (EUCAST 1.3), P=0.005; Enterobacter cloacae / cefepime, 97.0 (CLSI 2009) vs. 90.5% (EUCAST 1.3), P=0.012; Pseudomonas aeruginosa / meropenem, 88.1% (CLSI 2009) vs. 78.3% (EUCAST 1.3), P=0.002. These differences were still evident when comparing susceptibility rates according to the CLSI 2013 guideline with EUCAST 3.1 guideline. For P. aeruginosa and imipenem, a trend towards a lower antibiotic susceptibility rate in ICUs compared to general wards turned into a significant difference after the change to EUCAST: 87.9% vs. 79.8%, P=0.08 (CLSI 2009) and 86.3% vs. 76.8%, P=0.048 (EUCAST 1.3).

Conclusions: The change of AST guidelines from CLSI to EUCAST led to a clinically relevant decrease of susceptibility rates in cumulative antibiograms for defined species/drug combinations, particularly in those with considerable differences in clinical susceptibility breakpoints between the two guidelines.

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Different patterns of effects and distributions of inhibition zone diameters.Part A: Different “patterns of effects” when analysing period A according CLSI 2009 guidelines and period B according CLSI 2009 and EUCAST 1.3 guidelines; numbers are percent susceptible. Part B: Distribution of inhibition zone diameters of E.coli and cefepime: isolates of columns in black are not classified as “susceptible” any more when reported according to EUCAST 1.3 guidelines. Part C: Distribution of inhibition zone diameters of E. coli and meropenem: no change of susceptibility rate when EUCAST 1.3 guidelines are applied. Part D: Distribution of inhibition zone diameters of E. coli and amoxicillin/clavulanic acid: overlap of wild-type and resistent bacteria, leading to a change in classification from “intermediate” to “susceptible” (black column) of a near significant number of isolates when EUCAST 1.3 guidelines are applied.
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pone-0079130-g001: Different patterns of effects and distributions of inhibition zone diameters.Part A: Different “patterns of effects” when analysing period A according CLSI 2009 guidelines and period B according CLSI 2009 and EUCAST 1.3 guidelines; numbers are percent susceptible. Part B: Distribution of inhibition zone diameters of E.coli and cefepime: isolates of columns in black are not classified as “susceptible” any more when reported according to EUCAST 1.3 guidelines. Part C: Distribution of inhibition zone diameters of E. coli and meropenem: no change of susceptibility rate when EUCAST 1.3 guidelines are applied. Part D: Distribution of inhibition zone diameters of E. coli and amoxicillin/clavulanic acid: overlap of wild-type and resistent bacteria, leading to a change in classification from “intermediate” to “susceptible” (black column) of a near significant number of isolates when EUCAST 1.3 guidelines are applied.

Mentions: Four different “patterns” of effects on susceptibility rates were found when comparing the cumulative antibiograms of period A and period B by either interpreting the antibiograms according to CLSI 2009 or according to EUCAST 1.3 AST guidelines (Figure 1).


Change of antibiotic susceptibility testing guidelines from CLSI to EUCAST: influence on cumulative hospital antibiograms.

Wolfensberger A, Sax H, Weber R, Zbinden R, Kuster SP, Hombach M - PLoS ONE (2013)

Different patterns of effects and distributions of inhibition zone diameters.Part A: Different “patterns of effects” when analysing period A according CLSI 2009 guidelines and period B according CLSI 2009 and EUCAST 1.3 guidelines; numbers are percent susceptible. Part B: Distribution of inhibition zone diameters of E.coli and cefepime: isolates of columns in black are not classified as “susceptible” any more when reported according to EUCAST 1.3 guidelines. Part C: Distribution of inhibition zone diameters of E. coli and meropenem: no change of susceptibility rate when EUCAST 1.3 guidelines are applied. Part D: Distribution of inhibition zone diameters of E. coli and amoxicillin/clavulanic acid: overlap of wild-type and resistent bacteria, leading to a change in classification from “intermediate” to “susceptible” (black column) of a near significant number of isolates when EUCAST 1.3 guidelines are applied.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3815097&req=5

pone-0079130-g001: Different patterns of effects and distributions of inhibition zone diameters.Part A: Different “patterns of effects” when analysing period A according CLSI 2009 guidelines and period B according CLSI 2009 and EUCAST 1.3 guidelines; numbers are percent susceptible. Part B: Distribution of inhibition zone diameters of E.coli and cefepime: isolates of columns in black are not classified as “susceptible” any more when reported according to EUCAST 1.3 guidelines. Part C: Distribution of inhibition zone diameters of E. coli and meropenem: no change of susceptibility rate when EUCAST 1.3 guidelines are applied. Part D: Distribution of inhibition zone diameters of E. coli and amoxicillin/clavulanic acid: overlap of wild-type and resistent bacteria, leading to a change in classification from “intermediate” to “susceptible” (black column) of a near significant number of isolates when EUCAST 1.3 guidelines are applied.
Mentions: Four different “patterns” of effects on susceptibility rates were found when comparing the cumulative antibiograms of period A and period B by either interpreting the antibiograms according to CLSI 2009 or according to EUCAST 1.3 AST guidelines (Figure 1).

Bottom Line: The majority of species/drug combinations showed no differences in susceptibility rates comparing periods A and B.These differences were still evident when comparing susceptibility rates according to the CLSI 2013 guideline with EUCAST 3.1 guideline.For P. aeruginosa and imipenem, a trend towards a lower antibiotic susceptibility rate in ICUs compared to general wards turned into a significant difference after the change to EUCAST: 87.9% vs. 79.8%, P=0.08 (CLSI 2009) and 86.3% vs. 76.8%, P=0.048 (EUCAST 1.3).

View Article: PubMed Central - PubMed

Affiliation: Division of Infectious Diseases and Hospital Epidemiology, University Hospital and University of Zurich, Zurich, Switzerland.

ABSTRACT

Objective: We studied whether the change in antibiotic susceptibility testing (AST) guidelines from CLSI to EUCAST influenced cumulative antibiograms in a tertiary care hospital in Switzerland.

Methods: Antibiotic susceptibilities of non-duplicate isolates collected within a one-year period before (period A) and after (period B) changing AST interpretation from CLSI 2009 to EUCAST 1.3 (2011) guidelines were analysed. In addition, period B isolates were reinterpreted according to the CLSI 2009, CLSI 2013 and EUCAST 3.1 (2013) guidelines.

Results: The majority of species/drug combinations showed no differences in susceptibility rates comparing periods A and B. However, in some gram-negative bacilli, decreased susceptibility rates were observed when comparing CLSI 2009 with EUCAST 1.3 within period B: Escherichia coli / cefepime, 95.8% (CLSI 2009) vs. 93.1% (EUCAST 1.3), P=0.005; Enterobacter cloacae / cefepime, 97.0 (CLSI 2009) vs. 90.5% (EUCAST 1.3), P=0.012; Pseudomonas aeruginosa / meropenem, 88.1% (CLSI 2009) vs. 78.3% (EUCAST 1.3), P=0.002. These differences were still evident when comparing susceptibility rates according to the CLSI 2013 guideline with EUCAST 3.1 guideline. For P. aeruginosa and imipenem, a trend towards a lower antibiotic susceptibility rate in ICUs compared to general wards turned into a significant difference after the change to EUCAST: 87.9% vs. 79.8%, P=0.08 (CLSI 2009) and 86.3% vs. 76.8%, P=0.048 (EUCAST 1.3).

Conclusions: The change of AST guidelines from CLSI to EUCAST led to a clinically relevant decrease of susceptibility rates in cumulative antibiograms for defined species/drug combinations, particularly in those with considerable differences in clinical susceptibility breakpoints between the two guidelines.

Show MeSH
Related in: MedlinePlus