The aim of this study was to evaluate the performance of five different carbapenemase tests and to develop an algorithm which will permit the detection of most common and rare carbapenemases in routine microbiology laboratories. Methods: The immunochromatographic tests CARBA-5 (NG), RESIST-4 O.K.N.V. (Coris), the colorimetric b-CARBA (BioRad), a newly developed carbapenem-inactivation method (CIM) supplemented with zinc (zCIM), and the Xpert Carba-R (Cepheid) were challenged with a collection of 189 molecularly characterized Enterobacterales isolates, including 146 carbapenemase producers (CPE): VIM (n ¼ 48), OXA-48like (n ¼ 40), NDM (n ¼ 29), KPC (n ¼ 13), IMI (n ¼ 9), IMP (n ¼ 9), OXA-58 (n ¼ 2), and GES (n ¼ 2). Results: The overall sensitivity/specificity values for the five carbapenemase detection tests were 84.2% (CI 77.6e89.2%)/100% (CI 91.8e100%) for RESIST-4, 88.2% (CI 82.1e92.4%)/100% (CI 91.8e100%) for CARBA-5, 88.2% (CI 82.1e92.4%)/100% (CI 91.8e100%) for Xpert Carba-R, 73.7% (CI 66.2e80.0%)/100% (CI 93.4e99.0%) for b-CARBA, and 97.4% (CI 87.9e99.6%)/97.7% (CI 87.9e99.6%) for zCIM. The four common carbapenemases (KPC, OXA-48-like, NDM, and VIM) were detected with 97.6% sensitivity by all tests except for b-CARBA (76.6% (CI 68.4e83.2%)). IMI and GES were only detected by zCIM (sensitivity 90.9%(CI 62.3e98.4%)). Based on these results a new algorithm was developed, consisting of an immunochromatographic assay as the first test followed by zCIM, which allows detection of 99.3% of all carbapenemases assessed.Conclusions: Except for b-CARBA, all methods showed excellent sensitivity/specificity for the detection of the four most frequent carbapenemases. With the new algorithm, rare variants can also be detected. It is rapid, simple, and inexpensive and can be performed in any microbiology laboratory, as no PCR equipment is required.

One of the most demanding challenges in infection control is the worldwide dissemination of multidrug-resistant (MDR) bacteria in clinical settings. Especially the increasing prevalence of carbapenemase producing Gram-negative pathogens poses an urgent threat to public health, as these enzymes confer resistance to almost all β-lactam antibiotics including carbapenems. In this study, we report a prolonged nosocomial outbreak of various NDM-1-producing Enterobacterales species due to clonal spread and cross-species exchange of plasmids and possibly transposons. Between July 2015 and September 2017, a total of 51 carbapenemase-positive isolates were collected from 38 patients and three environmental sources in a single German hospital. Combining molecular typing methods and whole genome sequencing, the metallo-β-lactamase gene bla NDM-1 was found to be present in 35 isolates of which seven additionally carried the carbapenemase gene bla KPC-2. Core genome MLST (cgMLST) revealed different clusters of closely related isolates of Escherichia coli, Klebsiella pneumoniae, Citrobacter freundii, Morganella morganii or Enterobacter cloacae indicating clonal spread. The detailed reconstruction of the plasmid sequences revealed that in all outbreak-associated isolates bla NDM-1 was located on similar composite transposons, which were also very similar to Tn125 previously described for Acinetobacter baumannii. In contrast to Tn125, these structures were flanked by IS26 elements, which could facilitate horizontal gene transfer. Moreover, the identical plasmid was found to be shared by E. coli and M. morganii isolates. Our results highlight the importance of detailed genome-based analyses for complex nosocomial outbreaks, allowing the identification of causal genetic determinants and providing insights into potential mechanisms involved in the dissemination of antibiotic resistances between different bacterial species.

From June to October 2019, 17 patients (six infected, 11 colonised) with an extensively drug-resistant (XDR) Klebsiella pneumoniae strain were notified from four Western Pomerania medical facilities. The XDR K. pneumoniae produced carbapenemases NDM-1 and OXA-48, and was only susceptible to chloramphenicol, tigecycline and cefiderocol. Synergistic activity was observed for the combination of aztreonam plus ceftazidime-avibactam. Genomic analyses showed all isolates belonged to K. pneumoniae sequence type 307. Control measures and further investigations are ongoing.

Annually, increasing numbers of OXA-244-producing Escherichia coli in 13 German federal states prompted us to initiate an outbreak investigation. Whole genome sequencing revealed that among 148 isolates analysed, most belonged to sequence type 38 with 62 isolates forming a genetically distinct cluster. Although no epidemiological link could be identified between cases, ongoing investigations suggest non-healthcare associated transmission. A screening-PCR was developed facilitating early detection of ST38 cluster isolates to identify the source and transmission route.

No abstract