For the detection of carbapenemases in Acinetobacter the use of

imipenem has been chosen [6, 8] while for the detection of carbapenemases in Enterobacteriaceae meropenem is best validated but ertapenem has also been suggested [5, 7]. Most methods developed so far for this purpose have only investigated very small collections, in all 30 isolates, of P. aeruginosa[6, 7, 12] and only 10 isolates with a VIM enzyme out of which 9 were detected. [6, 12]. We this website included 25 isolates of P. aeruginosa out of which 14 carried a VIM enzyme and 1 an IMP-14-enzyme. Only 9 of these isolates could be detected (8 VIM and the only tested IMP positive isolate) using this method based on ertapenem. Both the VIM-type and absence of VIM-production

AG-881 could be ruled out as possible explanations for this. We therefore hypothesize that the non-hydrolysis of ertapenem might be due to additional porin loss resulting in a very low fraction of ertapenem (if any) to reach the periplasmatic site of action of the VIM-enzyme [13]. This finding is important as it shows that the local epidemiological situation where both the mechanism and species of interest may vary is important when choosing the PRIMA-1MET chemical structure right method for the detection of carbapenemases. However, when a carbapenemase was detected the use of inhibitor could verify the presence of a metallo-β-lactamase also in P. aeruginosa. The rapid verification (45–150 min including the preparation steps, incubation and MALDI-TOF analysis) of carbapenemase production separating KPC isolates from other carbapenemases is to our knowledge the most rapid verification method of carbapenemases in K. pneumoniae developed so far. As shown by others, direct detection of carbapenemase learn more production directly from blood culture vials is possible [4] and could be of great importance especially in hospitals with high incidence of carbapenemase producing isolates, as the rescue treatment in these cases is associated with worse patient outcome [14]. We did not have any IMP-producing

K. pneumoniae isolates available for this study and the specificity for KPC of the 15 min hydrolysis might thus be overrated. However the only IMP-producing P. aeruginosa isolate did not hydrolyse ertapenem in 15 min (data not shown). The method presented here is not dependent on any know-how in molecular biology and could be performed in any laboratory having access to a MALDI-TOF with open software allowing the manual analysis of mass spectra in a m/z range far below the range of 2–20 kDa used for species ID. We choose to build this assay on the hydrolysis of ertapenem as this hydrolysis is associated with specific degradation peaks of 472.5, 494.5, 516.5 and 538.5 easily visualized using the HCCA matrix used for species ID and does not need the addition of SDS (as compared to meropenem) [5]. The method accurately detection of KPCs in K.