and zone diameter
The website gives MIC and zone
diameter distributions for individual organisms and antimicrobial agents
in tables and wild type distributions in histograms. The MIC
distributions are based on collated data from an increasing total of
close to 20000 MIC distributions from worldwide sources. From December
2009 zone diameter distributions will be added and will be expanded
rapidly. Unless otherwise specifically stated, the MIC data are
representative of results obtained with a variety of MIC methods.
Different methods do not give exactly the same results but the results
rarely vary by more than one doubling dilution step. In this way the
aggregated MIC distributions encompass the variation between different
investigators and between different methods. Zone diameter distributions
are all based on the standardised EUCAST disk diffusion method (http://www.eucast.org/eucast_disk_diffusion_test/disk_diffusion_methodology/).
Clinical MIC and zone diameter breakpoints
shown to the right of the MIC or zone diameter distribution in the
tables and the bottom right-hand corner of each histogram in the form S<X/R>Y
mg/L for MICs or S>X/R<Y mm for zone diameters.
epidemiological cut-off value (ECOFF)
separates microorganisms without (wild type) and with acquired
resistance mechanisms (non-wild type) to the agent in question. The
epidemiological cut-off value is shown in the tables and the bottom
left-hand corner of each histogram in the form WT<X mg/L for MICs
or WT>X mm for zone diameters.
studies use different MIC ranges, which may particularly affect the
upper part of the MIC ranges. Distributions with severely truncated MIC
distributions are not included. Also the collated distributions include
studies from a wide variety of sources and time periods and some include
high proportions of resistant organisms, so the distributions must not
be used to represent rates of resistance to any agent and cannot be used
to compare resistance rates among agents.
cite data from the EUCAST program
We suggest the format
"European Committee on Antimicrobial Susceptibility Testing. Data from
the EUCAST MIC and zone diameter distribution website, last accessed Day
To contribute MIC
send data to
firstname.lastname@example.org. It is much appreciated if you
download and use one of the Excel files for bacteria or fungi, following
the instructions in the spreadsheet.
Frequently asked questions
is the purpose of the MIC and zone diameter distributions?
reference material for committees involved in decisions on clinical
reference material for epidemiological cut-off values for
antimicrobial resistance surveillance
reference MIC and zone diameter ranges of wild type organisms
for a wide spectrum of species and antimicrobials
international reference for calibration of antimicrobial
susceptibility testing methods.
are the sources of the data?
distributions include MICs from national and international studies such
as the BSAC, NORM, SENTRY, MYSTIC and GENARS resistance surveillance
programmes, as well as MIC distributions from published articles, the
pharmaceutical industry, veterinary programmes and individual
laboratories. Zone diameter distributions are from studies in reference
laboratories using the standardised EUCAST disk diffusion method.
MIC determination methods are represented?
The distributions represent MIC values
determined with methods described by ISO, EUCAST, BSAC (UK), CA-SFM
(France), CRG (The Netherlands), DIN (Germany), NWGA (Norway), SRGA
(Sweden) and CLSI (USA). Commercial MIC determination methods
standardized to any of the recognised methods are also included.
data obtained with a specific MIC method been excluded?
No specific method has been excluded.
Contributions are screened by the EUCAST Steering Committee and less
than 10% have been excluded from the aggregated distributions. However,
all data are held in the database and are accessible to the Steering
Committee. The most common reason for exclusion has been that the MIC
ranges were truncated (not full-range) so that a significant proportion
of MICs were outside the tested range (especially when at the low end of
is the origin of the organisms included in the MIC and zone diameter
are from tests on bacteria and fungi collected from man and animals, of
any geographic origin and over a wide timeframe.
does "Data not released for public use" imply?
the antimicrobials in the pull-down list are followed by the text "data
not released for public use". The process of harmonizing clinical
breakpoints across Europe and of defining the epidemiological cut-off
values is co-ordinated with the collection of relevant MIC data. As
decisions on MIC breakpoints are made for each group of antibiotics the
data are released for public use. Zone diameter distributions are
released as EUCAST zone diameter breakpoints are released.
can I get more information?
Contact EUCAST – email
addresses and information can be obtained through the EUCAST website at