title: Performance evaluation of three automated identification systems in detecting carbapenem-resistant Enterobacteriaceae.
abstract: BACKGROUND
  Carbapenem-resistant Enterobacteriaceae (CRE) is prevalent around the world. Rapid and accurate detection of CRE is urgently needed to provide effective treatment. Automated identification systems have been widely used in clinical microbiology laboratories for rapid and high-efficient identification of pathogenic bacteria. However, critical evaluation and comparison are needed to determine the specificity and accuracy of different systems. The aim of this study was to evaluate the performance of three commonly used automated identification systems on the detection of CRE.
  
  
  METHODS
  A total of 81 non-repetitive clinical CRE isolates were collected from August 2011 to August 2012 in a Chinese university hospital, and all the isolates were confirmed to be resistant to carbapenems by the agar dilution method. The potential presence of carbapenemase genotypes of the 81 isolates was detected by PCR and sequencing. Using 81 clinical CRE isolates, we evaluated and compared the performance of three automated identification systems, MicroScan WalkAway 96 Plus, Phoenix 100, and Vitek 2 Compact, which are commonly used in China. To identify CRE, the comparator methodology was agar dilution method, while the PCR and sequencing was the comparator one to identify CPE.
  
  
  RESULTS
  PCR and sequencing analysis showed that 48 of the 81 CRE isolates carried carbapenemase genes, including 23 (28.4 %) IMP-4, 14 (17.3 %) IMP-8, 5 (6.2 %) NDM-1, and 8 (9.9 %) KPC-2. Notably, one Klebsiella pneumoniae isolate produced both IMP-4 and NDM-1. One Klebsiella oxytoca isolate produced both KPC-2 and IMP-8. Of the 81 clinical CRE isolates, 56 (69.1 %), 33 (40.7 %) and 77 (95.1 %) were identified as CRE by MicroScan WalkAway 96 Plus, Phoenix 100, and Vitek 2 Compact, respectively. The sensitivities/specificities of MicroScan WalkAway, Phoenix 100 and Vitek 2 were 93.8/42.4 %, 54.2/66.7 %, and 75.0/36.4 %, respectively.
  
  
  CONCLUSIONS
  The MicroScan WalkAway and Viteck2 systems are more reliable in clinical identification of CRE, whereas additional tests are required for the Pheonix 100 system. Our study provides a useful guideline for using automated identification systems for CRE identification.
authors.affiliation: Department of Clinical Laboratory, Fujian Medical University Union Hospital, 29 Xinquan Rd., Fuzhou, 350001, Fujian, People's Republic of China.
authors.forename: Qingwen
authors.initials: Q
authors.lastname: He
authors.affiliation: Medical Technology and Engineering College, Fujian Medical University, Fuzhou, 350004, Fujian, People's Republic of China.
authors.forename: Weiyuan
authors.initials: W
authors.lastname: Chen
authors.affiliation: Medical Technology and Engineering College, Fujian Medical University, Fuzhou, 350004, Fujian, People's Republic of China.
authors.forename: Liya
authors.initials: L
authors.lastname: Huang
authors.affiliation: Medical Technology and Engineering College, Fujian Medical University, Fuzhou, 350004, Fujian, People's Republic of China.
authors.forename: Qili
authors.initials: Q
authors.lastname: Lin
authors.affiliation: Medical Technology and Engineering College, Fujian Medical University, Fuzhou, 350004, Fujian, People's Republic of China.
authors.forename: Jingling
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Medical Technology and Engineering College, Fujian Medical University, Fuzhou, 350004, Fujian, People's Republic of China.
authors.forename: Rui
authors.initials: R
authors.lastname: Liu
authors.affiliation: Department of Clinical Laboratory, Fujian Medical University Union Hospital, 29 Xinquan Rd., Fuzhou, 350001, Fujian, People's Republic of China. leonlee307@hotmail.com.
authors.forename: Bin
authors.initials: B
authors.lastname: Li
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D057205:Automation, Laboratory / Q000295:instrumentation / Q000592:standards*; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D015780:Carbapenems / Q000494:pharmacology; D004269:DNA, Bacterial / Q000235:genetics*; D004755:Enterobacteriaceae / Q000145:classification / Q000187:drug effects / Q000201:enzymology / Q000235:genetics*; D004756:Enterobacteriaceae Infections / Q000188:drug therapy / Q000382:microbiology; D015870:Gene Expression; D005838:Genotype; D006785:Hospitals, University; D006801:Humans; D008826:Microbial Sensitivity Tests; D016133:Polymerase Chain Reaction; D012680:Sensitivity and Specificity; D017422:Sequence Analysis, DNA; D018440:beta-Lactam Resistance / Q000235:genetics*; D001618:beta-Lactamases / Q000235:genetics* / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D015780:Carbapenems; D004269:DNA, Bacterial; D001618:beta-Lactamases; C063912:carbapenemase
keywords: Automated identification systems; Carbapenem-resistant Enterobacteriaceae; PCR