The etest method`s evaluation criterion was a 90% inhibition of growth in reading with reflected light, as defined in the notice. With this evaluation criterion, the Etest method showed categorical and essential matching levels of 90.0% and 92.0% compared to the results of the reference method for thinning the scraper. Etest had the highest percentage of very significant errors in staph (40.0%) under all MIC-based methods. S. aureus 3213, 3487, 3036, 5721 and 1458 and S. epidermidis-strains 7338 were all very bad errors (Table 2), as well as one strain of faecium (3419). Two of the very large errors (strains 3036 and 7338) were corrected after further testing by Etest (i.e. non-sensitive results). None of the very important errors were made with isolates that gave a slight growth. Three minor errors, all with strains of E.
faecium, have also been observed. Fifty staphylococcus isolates and 50 enterococci isolates were tested for linezolid sensitivity by broth micro-dilution, disc diffusion, Etest, MicroScan, Phoenix, VITEK and VITEK 2. The categorical and essential agreements on the results of the six micro-dilution methods are presented in Table 1.1. The results for each method are listed below. Isolates for which very significant or major errors have been reported are shown in Table 22. Among automated systems, MicroScan showed the highest category and essential match (96.0 and 99.0%), respectively, compared to the results of the reference method for micro-dilution of broth. Only one very serious error (a poorly receptive result) was detected for an epidermidis isolate (7338 with a documented C2534T mutation) initially reported by MicroScan as sensitive to lineline (MIC – 2 g/ml) but declared resistant in further tests (MIC, >4 g/ml) (Table2).2 It was also the only major error detected for the MicroScan system. Three minor errors, all with E. faecium isolates, varied into the non-receptive category (i.e., all results for both MicroScan and reference methods were either in the meantime or resistant), so that no non-linear-sensitive organisms remained undetectable.
Version 1.61 of the MicroScan software did not provide an interpretation of non-sensitive results for staphylococci (i.e., the scope of interpretation was empty in the reports). Category interpretations (sensitive, moderate or resistant) were provided for all outcomes for enterococci. (c) Category Convention (CA) – (consistent with the reference method / total organisms tested) X 100 cefazoline (left) and ceftriaxone (right) MIC distributions for Escherichia coli (mic.eucast.org/Eucast2/SearchController/search.jsp?action=performSearch&BeginIndex=0&Micdif=mic&NumberIndex=50&Antib=-1&Specium=162). It is expected that the approval rates of categorials for cefazolin will be lower, as the stopping points are the wild-type mic bisect distribution. S, fragile; I, intermediate step; R, resilient. Due to differences in the CLSI versions used in each AST system, all data was imported from each hospital to WHONET 5.6 software and interpreted according to the CLSI 2017 breakpoints at PUMCH to ensure consistency.8 The BMD results were considered a baseline.
