title: Evaluation of Phoenix Automated Microbiology System for detecting extended-spectrum beta-lactamases among chromosomal AmpC-producing Enterobacter cloacae, Enterobacter aerogenes, Citrobacter freundii, and Serratia marcescens.
abstract: We evaluated the BD Phoenix Extended-Spectrum beta-Lactamase (ESBL) detection test among chromosomal AmpC-producing Enterobacter cloacae, Enterobacter aerogenes, Citrobacter freundii, and Serratia marcescens. The study was conducted on 72 non-repetitive ESBL producers (33 E. cloacae, 13 E. aerogenes, 14 C. freundii, and 12 S. marcescens) and 77 ESBL non-producers (33 E. cloacae, 9 E. aerogenes, 6 C. freundii, and 29 S. marcescens). The organisms were selected as suspected ESBL-producers based on the double disk synergy test and confirmed by PCR amplification of blaTEM-1, blaSHV-1, blaCTX-M-1, blaCTX-M-2, and blaCTX-M-9. The Phoenix ESBL test, using a 5-well confirmatory test and the BDXpert system, was evaluated. Of the 72 isolates identified as ESBL-producers based on the DDST, 46 isolates harbored CTX-M-type enzymes, 21 harbored TEM type enzymes, and 31 harbored SHV enzymes. The Phoenix system identified ESBL only in 15 isolates. Of the 77 ESBL non-producers, ths Phoenix system identified ESBL in 4 isolates, 3 of which were confirmed to be ESBL-producers. In this study, the Phoenix system was highly specific (76/77, 98.7%), and it identified 3 additional ESBL-producers that were not detected by DDST. However, the Phoenix system's sensitivity was very low (15/72, 20.8%). Considering the increasing prevalence of ESBL production among AmpC-producers, the BD Phoenix system could not be considered a reliable stand-alone ESBL detection method for the strains tested in our study.
authors.affiliation: Department of Laboratory Medicine, College of Medicine, The Catholic University of Korea, Kangnam St. Mary's Hospital, 505 Banpo-dong, Seocho-ku, Seoul 137-701, Korea. yjpk@catholic.ac.kr
authors.forename: Yeon-Joon
authors.initials: YJ
authors.lastname: Park
authors.forename: Jin Kyung
authors.initials: JK
authors.lastname: Yu
authors.forename: Seungok
authors.initials: S
authors.lastname: Lee
authors.forename: Jung-Jun
authors.initials: JJ
authors.lastname: Park
authors.forename: Eun-Jee
authors.initials: EJ
authors.lastname: Oh
mesh_terms: D001426:Bacterial Proteins / Q000302:isolation & purification*; D016971:Citrobacter freundii / Q000201:enzymology*; D017931:DNA Primers; D021902:Enterobacter aerogenes / Q000201:enzymology*; D016972:Enterobacter cloacae / Q000201:enzymology*; D005069:Evaluation Studies as Topic; D007525:Isoelectric Focusing; D008828:Microbiological Techniques / Q000295:instrumentation / Q000379:methods*; D012680:Sensitivity and Specificity; D012706:Serratia marcescens / Q000201:enzymology*; D013045:Species Specificity; D001618:beta-Lactamases / Q000302:isolation & purification*
chemical_list: D001426:Bacterial Proteins; D017931:DNA Primers; C048795:AmpC beta-lactamases; D001618:beta-Lactamases