A MULTICENTER SURVEY OF RESISTANCE IN THE NETHERLANDS USING THE ETEST

To obtain data about the prevalence of resistance in bacterial isolate s causing serious infections in the Netherlands, a multicenter survey was carried out using the Etest for quantitative susceptibility testin g. More than 6000 isolates belonging to ten species were tested agains t eight antibiotics. Moreover, the Etest was validated against the aga r dilution method and the reproducibility of the Etest was studied. In spite of pH differences between the agar plates used for Etesting and agar dilution testing, a good correlation (that is 86%-97% within log , dilution steps) was found between both methods. Comparison of Etest values of the participating laboratories and the reference laboratory showed > 80% conformity within 1 log, dilution step and 90% within 2 l og, dilution steps, indicating a sufficient reproducibility of the Ete st. Resistance percentages were low for most species and antibiotics, relatively high percentages (10%-20%) indicating natural insusceptibil ity rather than development or increase of resistance.