A new method for normalized interpretation of antimicrobial resistance from disk test results for comparative purposes

Kronvall, G; Kahlmeter, Gunnar; Myhre, Erling B.; Galas, Marcelo

doi:10.1046/j.1469-0691.2003.00546.x

Cited by 70 publications

(62 citation statements)

References 22 publications

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“…The SOPs proposed for antibiotic studies address, among other things: the assessment of antibiotic resistance using a disc susceptibility test for various genera of microorganisms (Andrews 2001;Kronvall et al 2003;Wikler et al 2009a) and specifically, for aquaculture-organisms at international level (Huys et al 2005) and infrequently isolated or fastidious bacteria (Jorgensen et al 2005); broth dilution and disk diffusion antifungal susceptibility testing of yeasts (Rex et al 2008(Rex et al , 2009; and dilution antimicrobial susceptibility tests for aerobic bacteria (Wikler et al 2009b). …”

Section: Standardization Of Laboratory Proceduresmentioning

confidence: 99%

New trends in peptide-based anti-biofilm strategies: a review of recent achievements and bioinformatic approaches

2012

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Antimicrobial peptides (AMPs) have a broad spectrum of activity and unspecific mechanisms of action. Therefore, they are seen as valid alternatives to overcome clinically relevant biofilms and reduce the chance of acquired resistance. This paper reviews AMPs and anti-biofilm AMP-based strategies and discusses ongoing and future work. Recent studies report successful AMP-based prophylactic and therapeutic strategies, several databases catalogue AMP information and analysis tools, and novel bioinformatics tools are supporting AMP discovery and design. However, most AMP studies are performed with planktonic cultures, and most studies on sessile cells test AMPs on growing rather than mature biofilms. Promising preliminary synergistic studies have to be consubstantiated and the study of functionalized coatings with AMPs must be further explored. Standardized operating protocols, to enforce the repeatability and reproducibility of AMP anti-biofilm tests, and automated means of screening and processing the ever-expanding literature are still missing.

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Section: Standardization Of Laboratory Proceduresmentioning

confidence: 99%

New trends in peptide-based anti-biofilm strategies: a review of recent achievements and bioinformatic approaches

2012

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“…In recent years, the term epidemiological breakpoints or epidemiological cutoff (ECOFF), has been proposed by the European Committee on Antimicrobial Susceptibility Testing (EUCAST) to describe the upper MIC limit of the susceptible peak in an MIC distribution, the wild-type (WT) population. MIC distributions of WT isolates species-wise for many antimicrobials have been published on the internet by EUCAST and are publicly available (http://www.eucast.org/mic_distributions/) (5, 6).Normalized resistance interpretation (NRI) is an objective method to define the WT population in inhibition zone diameter histograms (4,8,10). The method has been used for setting interpretive breakpoints in an 18-year resistance surveillance, and also in an investigation of meropenem susceptibility in Pseudomonas aeruginosa (3,22).…”

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confidence: 99%

Normalized Resistance Interpretation as a Tool for Establishing Epidemiological MIC Susceptibility Breakpoints

Kronvall

2010

J Clin Microbiol

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Normalized resistance interpretation (NRI) utilizes the fact that the wild-type population on the sensitive side is not affected by resistance development, and therefore a normalized reconstruction of the peak can be performed Traditional concepts for setting interpretive breakpoints in antimicrobial susceptibility testing were challenged by J. D. Williams in 1990 when he proposed the setting of so-called microbiological guidelines in relation to the distribution of inhibition zone diameter values (or MIC values) of the susceptible population, for instance two standard deviations (SD) below the mode inhibition zone size (24). This would require a species-related aspect which was not yet accepted, although some reports on this issue had been published (2,12,14). Earlier, O'Brien had shown that an adjustment of interpretive breakpoints in relation to the susceptible peak in zone diameter histograms made results from different laboratories comparable and thereby foresaw later developments (17). In recent years, the term epidemiological breakpoints or epidemiological cutoff (ECOFF), has been proposed by the European Committee on Antimicrobial Susceptibility Testing (EUCAST) to describe the upper MIC limit of the susceptible peak in an MIC distribution, the wild-type (WT) population. MIC distributions of WT isolates species-wise for many antimicrobials have been published on the internet by EUCAST and are publicly available (http://www.eucast.org/mic_distributions/) (5, 6).Normalized resistance interpretation (NRI) is an objective method to define the WT population in inhibition zone diameter histograms (4,8,10). The method has been used for setting interpretive breakpoints in an 18-year resistance surveillance, and also in an investigation of meropenem susceptibility in Pseudomonas aeruginosa (3,22). It was recently used extensively in marine microbiology by P. . NRI was also used successfully to analyze Etest MIC data to set epidemiological breakpoints for tigecycline (11). However, a direct application of NRI to regular 2-fold dilution MIC results has not been possible because the mathematical calculations will be based on too few data points. The use of NRI has been extended in the present investigations to regular MIC values by the introduction of helper variables, and NRI has been evaluated as a method for the objective estimation of epidemiological breakpoints using the EUCAST MIC distributions as the material and as the reference (http://www.eucast .org/mic_distributions/). MATERIALS AND METHODSMIC distributions. The publicly available EUCAST MIC distributions include a large number of bacterial species and antimicrobials (http://www.eucast.org /mic_distributions/). For the purpose of testing the NRI method for MIC distributions in the present studies, results for Staphylococcus aureus and Escherichia coli were used. EUCAST claim on their website that the "Histograms display WT organisms." It is not clear, however, which method is used to ensure this selection in the published materials, which can include as ...

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“…Normalised resistance interpretation (NRI) was performed according to the method of Joneberg et al (2003), Kronvall (2003) and Kronvall et al (2003). Peak values were established using 5 point rolling means and the mean and standard deviation of the real distribution of fully susceptible (wild type) strains were calculated using a plot of probit values against zone size.…”

Section: Discussionmentioning

confidence: 99%

The advantages of the use of discs containing single agents in disc diffusion testing of the susceptibility of Aeromonas salmonicida to potentiated sulphonamides

Douglas¹,

Ruane²,

Geary³

et al. 2007

Aquaculture

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The susceptibilities of 106 strains of Aeromonas salmonicida to trimethoprim/sulfamethoxazole (SFT) were determined in two laboratories using the Clinical and Laboratory Standards Institute's M42-A disc diffusion protocols. The data generated by the use of discs containing 25 μg SFT (SFT25) allowed the strains to be placed into two groups. Strains in one group (17 strains) generated no inhibition zones and the zones obtained from the other 89 strains were distributed over a wide range but showed no natural division into separate sub-classes. A further investigation performed by one of the participating laboratories, of the susceptibility of 91 of these 106 strains used discs containing 100 μg sulfmethoxazole (SFM100) and 5 μg trimethoprim (TMP5). Application of normalised resistance interpretation to these data allowed the estimation of epidemiological cut-off values for WT strains of ≥ 9 mm for SFM100 and ≥ 21 mm for TMP5. This investigation demonstrated the presence of three distinct phenotypic classes, one containing strains manifesting wild type susceptibility to both agents, another containing strains manifesting non-wild type susceptibility to both and a third containing strains manifesting wild type susceptibility with respect to TMP but non-wild type with respect to SFM. Analysis demonstrated the inability of SFT25 discs to generate data that allowed the separate identification of strains that were fully susceptible to both TMP and SFM from those that were fully susceptible to TMP but were not fully susceptible to SFM.It is recommended that, in investigation of the susceptibility to potentiated sulphonamides of isolates from diseased fish, separate discs, containing the individual components of the mixture, should be employed.

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A new method for normalized interpretation of antimicrobial resistance from disk test results for comparative purposes

Abstract: The normalized resistance interpretation offers a new approach to comparative surveillance studies whereby the inhibition zone diameter results from disk tests in clinical laboratories can be used for calibration of the test.

Cited by 70 publications

References 22 publications

New trends in peptide-based anti-biofilm strategies: a review of recent achievements and bioinformatic approaches

New trends in peptide-based anti-biofilm strategies: a review of recent achievements and bioinformatic approaches

Normalized Resistance Interpretation as a Tool for Establishing Epidemiological MIC Susceptibility Breakpoints

The advantages of the use of discs containing single agents in disc diffusion testing of the susceptibility of Aeromonas salmonicida to potentiated sulphonamides

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