title: Development of an algorithm for phenotypic screening of carbapenemase-producing Enterobacteriaceae in the routine laboratory.
abstract: Carbapenemase-producing Enterobacteriaceae (CPE) are difficult to identify among carbapenem non-susceptible Enterobacteriaceae (NSE). We designed phenotypic strategies giving priority to high sensitivity for screening putative CPE before further testing.
  
  
  
  Presence of carbapenemase-encoding genes in ertapenem NSE (MIC > 0.5 mg/l) consecutively isolated in 80 French laboratories between November 2011 and April 2012 was determined by the Check-MDR-CT103 array method. Using the Mueller-Hinton (MH) disk diffusion method, clinical diameter breakpoints of carbapenems other than ertapenem, piperazicillin+tazobactam, ticarcillin+clavulanate and cefepime as well as diameter cut-offs for these antibiotics and temocillin were evaluated alone or combined to determine their performances (sensitivity, specificity, positive and negative likelihood ratios) for identifying putative CPE among these ertapenem-NSE isolates. To increase the screening specificity, these antibiotics were also tested on cloxacillin-containing MH when carbapenem NSE isolates belonged to species producing chromosomal cephalosporinase (AmpC) but Escherichia coli.
  
  
  
  Out of the 349 ertapenem NSE, 52 (14.9%) were CPE, including 39 producing OXA-48 group carbapenemase, eight KPC and five MBL. A screening strategy based on the following diameter cut offs, ticarcillin+clavulanate <15 mm, temocillin <15 mm, meropenem or imipenem <22 mm, and cefepime <26 mm, showed 100% sensitivity and 68.1% specificity with the better likelihood ratios combination. The specificity increased when a diameter cut-off <32 mm for imipenem (76.1%) or meropenem (78.8%) further tested on cloxacillin-containing MH was added to the previous strategy for AmpC-producing isolates.
  
  
  
  The proposed strategies that allowed for increasing the likelihood of CPE among ertapenem-NSE isolates should be considered as a surrogate for carbapenemase production before further CPE confirmatory testing.
authors.affiliation: Sorbonne Universités, UPMC Univ Paris 06, INSERM, U1135, Centre d'Immunologie et des Maladies Infectieuses (CIMI), Eq 13, F-75013, Paris, France. jerome.robert0@upmc.fr.|Bactériologie-Hygiène, Hôpitaux Universitaires Pitié Salpêtrière - Charles Foix, APHP, F-75013, Paris, France. jerome.robert0@upmc.fr.
authors.forename: Jérôme
authors.identifier: 0000-0002-9380-0570
authors.initials: J
authors.lastname: Robert
authors.affiliation: INSERM U1047, UFR de Médecine, Université Montpellier 1, Nîmes, France.|Service de Microbiologie, CHU Carémeau, Nîmes, France.
authors.forename: Alix
authors.initials: A
authors.lastname: Pantel
authors.affiliation: Laboratoire de biologie, Hôpital d'Instruction des Armées Bégin, Saint- Mandé, France.
authors.forename: Audrey
authors.initials: A
authors.lastname: Merens
authors.affiliation: Service de Microbiologie, Hôpital Beaujon AP-HP, Clichy, France.
authors.forename: Elodie
authors.initials: E
authors.lastname: Meiller
authors.affiliation: INSERM U1047, UFR de Médecine, Université Montpellier 1, Nîmes, France.|Service de Microbiologie, CHU Carémeau, Nîmes, France.
authors.forename: Jean-Philippe
authors.initials: JP
authors.lastname: Lavigne
authors.affiliation: Service de Microbiologie, Hôpital Beaujon AP-HP, Clichy, France.|Faculté de Médecine D. Diderot - Paris 7, Paris, France.|INSERM UMR 1137, Université Paris 7, Paris, France.
authors.forename: Marie-Hélène
authors.initials: MH
authors.lastname: Nicolas-Chanoine
mesh_terms: D000465:Algorithms; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000032:analysis* / Q000378:metabolism; D015780:Carbapenems / Q000378:metabolism* / Q000494:pharmacology; D000077723:Cefepime; D002511:Cephalosporins / Q000494:pharmacology; D002969:Clavulanic Acids / Q000494:pharmacology; D024881:Drug Resistance, Bacterial; D004755:Enterobacteriaceae / Q000187:drug effects / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D000077727:Ertapenem; D006801:Humans; D015378:Imipenem / Q000378:metabolism / Q000494:pharmacology; D000077731:Meropenem; D008826:Microbial Sensitivity Tests; D010397:Penicillanic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D010406:Penicillins / Q000494:pharmacology; D000078142:Tazobactam; D013845:Thienamycins / Q000378:metabolism / Q000494:pharmacology; D013982:Ticarcillin / Q000494:pharmacology; D001618:beta-Lactamases / Q000032:analysis* / Q000378:metabolism; D047090:beta-Lactams / Q000378:metabolism / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D015780:Carbapenems; D002511:Cephalosporins; D002969:Clavulanic Acids; D010406:Penicillins; D013845:Thienamycins; D047090:beta-Lactams; C031367:temocillin; D015378:Imipenem; D000077723:Cefepime; C043215:ticarcillin-clavulanic acid; D010397:Penicillanic Acid; D001618:beta-Lactamases; C063912:carbapenemase; D013982:Ticarcillin; D000077731:Meropenem; D000077727:Ertapenem; D000078142:Tazobactam
keywords: Algorithm; Carbapenemase; Disk diffusion method; Enterobacteriaceae; Screening