title: Comparison of 3 phenotypic-detection methods for identifying plasmid-mediated AmpC beta-lactamase-producing Escherichia coli, Klebsiella pneumoniae, and Proteus mirabilis strains.
abstract: BACKGROUND
  Plasmid-mediated AmpC beta-lactamases (PABLs) have been detected in the strains of Escherichia coli, Klebsiella spp., Proteus mirabilis, and Salmonella spp. PABLs may be difficult to detect and might interfere in the therapeutic and infection-control processes. Although several PABL-detection methods based on phenotypes have been reported, the Clinical and Laboratory Standards Institute currently does not recommend a routine detection method for PABLs. The aim of this study is to compare the performances of 3 phenotypic PABL detection methods.
  
  
  METHODS
  Total 276 non-duplicated clinical isolates of E. coli (N=97), K. pneumoniae (N=136), and P. mirabilis (N=43) were collected from 14 hospitals in Korea between April and June 2007 in a non-consecutive and non-random manner. Multiplex PCR was performed to detect the PABL genes. Further, 3 phenotypic detection methods-cephamycin-Hodge test, Tris-EDTA (TE) disk test, and combination-disk test with 3-aminophenylboronic acid (BA)-were performed using cefoxitin and cefotetan disks.
  
  
  RESULTS
  PABL genes were detected by multiplex PCR in 122/276 isolates, including 14/97 E. coli, 105/136 K. pneumoniae, and 3/43 P. mirabilis isolates. The combination-disk test with BA showed higher sensitivity (98.4%), specificity (92.2%), and efficiency (96.3%) than the cephamycin-Hodge (76.2%, 96.1%, and 88.6%, respectively) and the TE-disk (80.3%, 91.6%, and 87.9%, respectively) tests.
  
  
  CONCLUSIONS
  The combination-disk test with BA is a simple, efficient, and interpretable test that can be applicable in clinical laboratories involved in the detection of PABLs in clinical isolates of E. coli, K. pneumoniae, and P. mirabilis.
authors.affiliation: Department of Laboratory Medicine, CHA University, Sungnam, Korea.
authors.forename: Wookeun
authors.initials: W
authors.lastname: Lee
authors.forename: Bochan
authors.initials: B
authors.lastname: Jung
authors.forename: Seong Geun
authors.initials: SG
authors.lastname: Hong
authors.forename: Wonkeun
authors.initials: W
authors.lastname: Song
authors.forename: Seok Hoon
authors.initials: SH
authors.lastname: Jeong
authors.forename: Kyungwon
authors.initials: K
authors.lastname: Lee
authors.forename: Hyo Sun
authors.initials: HS
authors.lastname: Kwak
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000032:analysis*; D015313:Cefotetan / Q000494:pharmacology; D002440:Cefoxitin / Q000494:pharmacology; D052978:Disk Diffusion Antimicrobial Tests / Q000379:methods*; D004926:Escherichia coli / Q000235:genetics / Q000302:isolation & purification*; D006801:Humans; D007711:Klebsiella pneumoniae / Q000235:genetics / Q000302:isolation & purification*; D010641:Phenotype; D010957:Plasmids; D011513:Proteus mirabilis / Q000235:genetics / Q000302:isolation & purification*; D012680:Sensitivity and Specificity; D001618:beta-Lactamases / Q000032:analysis*
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D015313:Cefotetan; D002440:Cefoxitin; C048795:AmpC beta-lactamases; D001618:beta-Lactamases