We evaluated the accuracy of the BD Phoenix system for the identification (ID) and antimicrobial susceptibility testing (AST) of 251 isolates of the family Enterobacteriaceae representing 31 species. Organisms were inoculated onto the Phoenix panel according to the manufacturer's instructions. The results from conventional biochemical tests were used for the reference method for ID. Agar dilution, performed according to the CLSI guidelines, was the reference AST method. Essential and categorical agreements were determined. The overall levels of agreement for the genus-and species-level identifications were 95.6% and 94.4%, respectively. Fourteen isolates were incorrectly identified by the Phoenix system; 10 of these were incorrectly identified to the species level. Three of these were Enterobacter (Pantoea) species and four of these were Shigella spp. misidentified as Escherichia coli. For AST results, the essential and categorical agreements were 98.7% and 97.9%, respectively. The very major error, major error, and minor error rates were 0.38%, 0.33%, and 1.8%, respectively. Six isolates (three E. coli isolates and three Klebsiella isolates) were extended-spectrum -lactamase producers. All six were flagged by the Phoenix system expert rules. The Phoenix system compares favorably to traditional methods for ID and AST of Enterobacteriaceae.As hospitals face the continuing challenge of treating sicker patients, the burden falls to clinical microbiology laboratories to provide accurate and rapid identification (ID) of the pathogens recovered and, more importantly, to detect antimicrobial resistance. To accomplish this goal, many laboratories rely upon automated microbial identification and antimicrobial susceptibility testing (AST) systems. The newer-generation instruments have more extensive databases; data management tools, including expert systems; and other features unique to each manufacturer. The BD Phoenix automated microbiology system (BD Diagnostic Systems, Sparks, MD) is the newest system to obtain clearance from the Food and Drug Administration.We evaluated the performance of the Phoenix instrument for the identification and susceptibility testing of challenge and clinical isolates of the family Enterobacteriaceae isolated from a variety of specimen sources in a busy tertiary-care medical center. MATERIALS AND METHODSBacterial strains. A total of 251 bacterial isolates were used for this evaluation. A total of 76 archived "challenge" gram-negative bacilli, including 19 isolates of Shigella spp. from Bangladesh, and 175 clinical isolates recovered from routine cultures in the Clinical Microbiology Laboratory of the Johns Hopkins Hospital (JHH) were included in this comparison.Reference identification. The laboratory's routine method for the identification of gram-negative organisms includes testing with the following conventional biochemicals. For Enterobacteriaceae, the following biochemicals incorporated into an in-house agar system were used: colistin, cefazolin, oxidase, phenylalanine deaminase, urea...
We evaluated the Phoenix automated microbiology system (BD Diagnostic Systems, Sparks, MD) for the identification (ID) and antimicrobial susceptibility testing (AST) of challenge and clinical staphylococci and enterococci recovered from patients in a tertiary-care medical center. In total, 424 isolates were tested: 90 enterococci; 232 Staphylococcus aureus isolates, including 14 vancomycin-intermediate S. aureus isolates; and 102 staphylococci other than S. aureus (non-S. aureus). The Phoenix panels were inoculated according to the manufacturer's instructions. The reference methods for ID comparisons were conventional biochemicals and cell wall fatty acid analysis with the Sherlock microbial identification system (v 3.1; MIDI, Inc. Newark, DE). Agar dilution was the reference AST method. The overall rates of agreement for identification to the genus and the species levels were 99.7% and 99.3%, respectively. All S. aureus isolates and enterococci were correctly identified by the Phoenix panels. For the non-S. aureus staphylococci, there was 98.0% agreement for the ID of 16 different species. The AST results were stratified by organism group. For S. aureus, the categorical agreement (CA) and essential agreement (EA) were 98.2% and 98.8%, respectively. Three of three very major errors (VMEs; 1.7%) were with oxacillin. For non-S. aureus staphylococci, the CA, EA, VME, major errors, and minor error rates were 95.7%, 96.8%, 0.7%, 1.7%, and 2.9%, respectively. The two VMEs were with oxacillin. For the enterococci, there was 100% CA and 99.3% EA. All 36 vancomycin-resistant enterococci were detected by the Phoenix system. The Phoenix system compares favorably to traditional methods for the ID and AST of staphylococci and enterococci.The burden of the rapid and accurate detection of antimicrobial resistance among gram-positive bacteria remains a continuous challenge for clinical microbiology laboratories. The last decade has seen increases in the numbers of vancomycinresistant enterococcal (VRE) infections (11, 18), the appearance of glycopeptide resistance among staphylococci (15, 18), a continued rise in nosocomial methicillin-resistant Staphylococcus aureus (MRSA) isolates (9, 11), and a surge in communityassociated MRSA isolates (5,12,19). In addition, other staphylococci continue to cause serious nosocomial infections, such as endocarditis caused by S. lugdunensis and infections of intravascular and prosthetic devices caused primarily by S. epidermidis (1, 7, 13). This fact, combined with the change in breakpoints for oxacillin/methicillin testing of coagulase-negative staphylococci (10), has presented additional challenges for laboratories, which must adopt systems with improved abilities for the identification (ID) and antimicrobial susceptibility testing (AST) of non-S. aureus staphylococci.The newer automated instruments have more extensive databases, data management tools (including expert systems), and other features unique to the instrument of each manufacturer. In addition, the accuracy of susceptibility tes...
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