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Dutch laboratories are currently changing their breakpoint criteria from mostly Clinical Laboratory and Standards Institute (CLSI) breakpoints to European Committee on Antimicrobial Susceptibility Testing (EUCAST) breakpoints. To evaluate the impact of these changes, we studied antimicrobial resistance trends of Escherichia coli in blood specimens from January 2008 to January 2012 using CLSI and EUCAST breakpoints and compared them with the antimicrobial susceptibility test (AST) interpretations reported by Dutch laboratories participating in the Infectious Disease Surveillance Information System for Antibiotic Resistance (ISIS-AR). ISIS-AR collects AST interpretations, including underlying minimal inhibitory concentrations (MICs) of routinely cultured bacterial species on a monthly basis from Dutch laboratories. MICs of Etests or automated systems were reinterpreted according to the CLSI 2009 and EUCAST 2010 guidelines. Trends in non-susceptibility (i.e. intermediate resistant and resistant) over time were analysed by the Cochran-Armitage test for trend. The effects of the change from CLSI to EUCAST breakpoints on non-susceptibility were small. There were no differences in non-susceptibility to amoxicillin, amoxicillin/clavulanic acid, cefuroxim, gentamicin and co-trimoxazol and only small differences (1-1.5%) for ciprofloxacin between AST interpretations by CLSI or EUCAST. However, for ceftazidime, and cefotaxime/ceftriaxone the proportion of non-susceptibility was substantially higher when EUCAST breakpoints were used (2-3%). The effects on time trends of the change in guidelines were limited, with only substantial differences for the oxymino-cephalosporins. Our study shows that the implementation of EUCAST breakpoints has a limited effect on the proportion of non-susceptible isolates and time trends in E. coli for most, but not all, antimicrobial agents., (© 2012 The Authors. Clinical Microbiology and Infection © 2012 European Society of Clinical Microbiology and Infectious Diseases.)

From January 2003 to December 2005, 5091 susceptibility test results from invasive isolates of Escherichia coli, collected from blood cultures and cerebrospinal fluid routinely processed within 58 participating laboratories, were investigated. These laboratories in turn serviced 64 hospitals in Algeria, Cyprus, Egypt, Jordan, Lebanon, Malta, Morocco, Tunisia and Turkey. The median proportion of resistance to third-generation cephalosporins for the duration of the project was 18.9% (interquartile range (IQR): 12.5–30.8%), and for fluoroquinolones 21.0% (IQR: 7.7–32.6%). A substantial proportion of strains reported by laboratories in countries east of the Mediterranean exhibited evidence of multiresistance, the highest proportion being from Egypt (31%). There is clearly a need for further investigation of potential causes of the significant resistance identified, as well as for strengthening of national and international surveillance initiatives within this region.` [ABSTRACT FROM AUTHOR]