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February 2011

Report on change to EUCAST recommendations using ROSCO Neo-Sensitabs EUCAST potency. Aalborg University Hospital, Denmark Early 2010 we changed our susceptibility testing methods from using Muller Hinton agar with semi-confluent growth and Danish breakpoints to EUCAST guidelines, using Muller Hinton agar with McFarland 0.5 inoculum and EUCAST breakpoints. Changing from old potency ROSCO Neo-Sensitabs to EUCAST potency also included a change of dispensers, which meant that we had to replace our round agar plates with square ones. We prepared carefully for the switch by having two supervisors, a clinical microbiologist and a very skilled technician, testing both clinical isolates and quality controls prior to the change. They also joined a course on EUCAST methods held by Swedish microbiologists who had been working intensely with the method. The supervisors did the training of the laboratory technicians in preparing the inoculum, setting the plates as well as reading them with the higher inoculum including new interpretations according to EUCAST. Getting used to reading from the backside of the plates without using a magnifying glass, but taking notice of the slightest growth visible with the naked eye took some time. We also learned that the position of the light were crucial to the result. We experienced that the thorough training of every single technician, including testing that the EUCAST recommendation were followed meticulously by everyone before starting processing clinical specimens, made the change go rather easy and uncomplicated. The extra workload preparing the shift and implementing the EUCAST guidelines did cost a certain amount of money as it was time consuming for both the two supervisors (about 3 months work) and all the technicians and other working staff. It was of cause a tough and hard process, because it included several changes to our previous procedures, but it came out at the end with very nice results and Quality Control zones that were mostly within target. During the changing process we were in close contact with ROSCO Diagnostica WHO gave us excellent help in preparing the switch as well as in solving many practical problems. The people from ROSCO were most helpful in answering all of our questions. Today, one year later, most of our QC testing are within the target, including Ampicillin 10 µg, Mecillinam 10 µg, Piperacillin/Tazobactam 36 µg, Cefuroxime 30 µg, Cefotaxime 5 µg,, Ceftazidime 10 µg, Cefoxitin 30 µg, Ertapenem 10 µg, Gentamicin 10 µg, Ciprofloxacin 5 µg, Sulphonamides, and Trimethoprim 5 µg, being the most currently used. As for Haemophilus influenzae we still have problems in reaching the target values for the controls and susceptibility testing of clinical isolates often indicates betalactamase negative ampicillin resistance (too small zonesizes for cefachlor) , which cannot be confirmed by E-test. We are now satisfied with the change to EUCAST MIC/zone breakpoints recommendations, also because it enables us to communicate our results to other colleagues in Europe. Tove Højbjerg Consultant Department of Clinical microbiology Aalborg University Hospital, Denmark