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Carbapenems are last resort antibiotics used in infections caused by multidrug-resistant bacteria. Carbapenem-resistant Enterobacteriaceae infections are an increasingly global threat, especially because carbapenemase production is more frequent than other resistance mechanisms and is encoded by genes located on transferable genetic structures. The production of classes A (KPC), B (IMP, VIM, NDM) and D (OXA-48 and its variants) of carbapenemases has important clinical consequences and is a constant pool of resistance. This review tries to show the diversity of carbapenemases and to underline their importance. [ABSTRACT FROM AUTHOR]

Objectives: Detection of carbapenemase-producing Enterobacterales (CPEs) is sometimes difficult with AmpC-hyperproducing Enterobacterales (AHEs), as they may falsely be classified as CPEs. Here, we present a rapid Carbapenem Inactivation Method (rCIM) optimized for AmpC producers (rCIM-A) that allows rapid and easy discrimination between AHEs and CPEs.Methods: Enterobacterales (n = 249), including natural AmpC producers, AHEs, CPEs and non-carbapenemase-producing carbapenem-resistant control strains were evaluated, using Carba NP, rCIM and rCIM-A. The rCIM-A differs from the rCIM by the addition of cloxacillin (400 μg/mL) to the initial antibiotic incubation step.Results: The rCIM-A yielded a sensitivity and specificity of 84.26% (95% CI: 76.00%-90.55%) and 99.29% (95% CI: 96.11%-99.98%), respectively, while those of the rCIM were 86.11% (95% CI: 78.13%-92.01%) and 80.85% (95% CI: 73.38%-86.99%), respectively; those of Carba NP were lower at 84.04% (95% CI: 75.05%-90.78%) and 91.37% (95% CI: 85.41%-95.46%), respectively, due to indeterminate results. The rCIM-A was capable of discriminating between AHEs and true CPEs, but still failed to identify OXA-23-producing Proteus mirabilis isolates and remained only partially reliable for identifying IMI-like producers and a few MBL (2 NDM-1, 1 LMB-1, 1 TMB-1 and 1 IMP-13) producers. One chromosomally encoded AmpC variant, MIR-10, gave repeatedly positive results using all three tests and was thus considered a false positive.Conclusions: Specificity for AHEs greatly improved with the rCIM-A without altering the test performance for the other resistance mechanisms. It may replace the rCIM as a cheap, easy, rapid and accurate CPE detection test. [ABSTRACT FROM AUTHOR]

Objectives: Fast and accurate diagnostic tests to identify carbapenemase-producing Enterobacteriaceae (CPE) are mandatory for proper antimicrobial therapy and implementing infection control measures. Here, we have developed a rapid Carbapenem Inactivation Method (rCIM) for CPE detection. Methods: The rCIM consists of the incubation of a potential carbapenemase producer with meropenem discs and use of the resulting supernatant to challenge a susceptible indicator strain. Growth of the indicator strain is monitored using a nephelometer. The performances of the rCIM were compared with theCIM and Carba NPtests using a collection of 113 well-characterized carbapenem-resistant enterobacterial isolates, including 85 carbapenemase producers and 28 non-carbapenemase producers. In addition, rCIM was compared with the Carba NP test and PCR sequencing in a prospective analysis of 101 carbapenem-resistant enterobacterial isolates addressed to the French National Reference Center for Antimicrobial Resistance in July 2017. Results and discussion: The rCIM correctly identified 84/85 carbapenemase producers and 28/28 non-carbapenemase producers, yielding a sensitivity of 99% and a specificity of 100%, slightly higher than the CIM and Carba NP test. In the prospective validation study, the rCIM showed a sensitivity and specificity of 97% and 95%, respectively. Two cephalosporinase-hyperproducing Enterobacter cloacae gave false-positive results, whereas an IMI-17-producing Enterobacter asburiae gave a false-negative result. The result was, however, positive when the isolate was grown on selective antibiotic-containing media. Conclusions: The rCIM is a rapid (less than 3 h), cheap and accurate test for the detection of CPEs, which can be implemented in low-resource settings, making it a useful tool for microbiology laboratories. [ABSTRACT FROM AUTHOR]

Introduction. Resistance to carbapenems represents a public health across the world. Screening for carbapenem resistance can be done starting from the antibiogram, but confirmatory methods are usually performed in reference centers. Methods for rapid identification of carbapenemase activity are required to empower laboratories to detect carbapenemases and raise signals for infectious disease physicians, antibiotic stewardship teams and hospital hygiene specialists. Materials and methods. Eppendorf tubes containing Klebsiella pneumoniae strains with carbapenemase activity (KPC-1, NDM-1, OXA-48) and others with no carbapenemase activity (K. pneumoniae ATCC 700603 and E. coli ATCC 25922), as well as positive and negative controls were incubated at 37 °C with varying concentrations of Meropenem. After incubation, samples were spun down until a pellet formed and the supernatant was used to challenge an exponentially growing E. coli culture. This second culture was followed with nephelometric measurements every half hour. Experiments were carried out in three technical replicates. The statistical analysis was done with R (version 3.3.3) and graphs generated in RStudio (version 1.0.136) with ggplot2 (version 2.1.0). Mann Whitney U Test with the assumption of independent samples was used to analyse the results. Results. The doses of Meropenem were chosen after dose ranging experiments and multiple incubation times (from 30 minutes to two hours) were tested in order to evaluate the robustness of the method. In the cases where the antibiotic was first incubated with strains that had carbapenemase activity, the growth of Escherichia coli ATCC 25 922 was non-hindered, matching that of controls. In the absence of carbapenemase activity and in the case of negative controls, the growth indicator strain was inhibited. Statistically significant differences were identified for 0.3, as well as a 0.5 McFarland index as early as 1.5 hours total work time. Conclusions. The discovery of carbapenem resistance has direct clinical, as well as epidemiological implications. Among the mechanisms implicated in resistance to carbapenems, the presence of a carbapenemase is one of the most worrying from an epidemiological standpoint. This new tool we describe herein can be performed in all clinical microbiology laboratories, with no extra expense (as opposed to CarbaNP and BlueCarba tests). [ABSTRACT FROM AUTHOR]