This study shows very good results for ID of Enterobacteriaceae. Only two errors Selleck ICG-001 occurred with ID in this group. One strain was not identified and one strain of E. coli was misidentified as S. choleraesuis. Results of ID for Pseudomonas species were less reliable. Both errors in this group were P. aeruginosa strains that were identified

as P. fluorescens, a rare cause of bloodstream infections. These misidentifications did not lead to errors in interpretation of AST, but rare or unlikely results of ID should be dealt with carefully and be confirmed using additional tests. Other studies also showed that ID of non-fermenting GNR was less reliable than that of Enterobacteriaceae [18, 23]. This may be due to the lower growth rate of non-fermenters, which could result in weaker fluorescent biochemical reactions in the Phoenix ID panel. Errors in ID with the direct method could also be caused by traces of blood culture components in the ID broth. This however

seems less likely, since with Enterobacteriaceae, errors in ID were rare. Since the Phoenix system was not used for ID of GPC, ID by direct inoculation was not tested in this group. But since ID is required for interpretation of AST, in clinical practice, rapid AST will have to be combined with a rapid method of ID, such as PCR-based methods on whole blood, like LightCycler® SeptiFast Test MGRADE (Roche), VYOO Sepsis Test (SIRS-Lab), SepsiTest™ (Molzym), or MALDITOF-MS on positive blood cultures [24]. Some studies on direct methods for AST showed poor results for GPC [15, 16] or focus on GNR MAPK inhibitor only due to unfavorable results for GPC [17]. However, in this

study, direct AST for Staphylococcus species and Enterococcus species showed good agreement with conventional methods, comparable to results of the standard method, but with fewer very major errors. Lupetti et al. [19], who tested the direct Chloroambucil Phoenix method for GPC and compared their results with those of the Vitek 2, found an even higher agreement. They incubated a portion of the positive blood culture with saponin in order to harvest more bacteria from a positive blood culture through the release of intracellular bacteria. Other studies that presented results of direct methods for AST of GPC showed variable results [13–16, 25, 26], which makes comparison difficult. But our results were comparable to those of the routine Phoenix method. Moreover, categorical agreement for most tested antibiotics in this study, including oxacillin and vancomycin, were well over 90% and the percentage of major and very major errors is low, meeting the standards proposed by Jorgensen et al. [27]. Only erythromycin and trimethoprim-sulfamethoxazole showed lower agreements. The majority of errors for erythromycin were minor errors, but also some major errors occurred. Trimethoprim-sulfamethoxazole was the only antibiotic for both GPC and GNR showing very major errors.