title: Use of the Phoenix automated system for identification of Streptococcus and Enterococcus spp.
abstract: The Phoenix system (Becton Dickinson Diagnostic Systems, Sparks, MD) was evaluated for identification (ID) to the species level of streptococci and enterococci. Two hundred clinical isolates were investigated: beta-hemolytic streptococci (n = 50), Streptococcus pneumoniae organisms (n = 46), viridans group streptococci (n = 31), Enterococcus faecium (n = 36), Enterococcus faecalis (n = 25), and other catalase-negative cocci (n = 12). The API system (bioMérieux, Marcy l'Etoile, France) was used as a comparator. Molecular methods (sequencing of 16S rRNA and zwf and gki genes and ddl gene amplification) were used to investigate discordant results. Upon resolution of discrepancies, correct species ID was achieved by the Phoenix system for 121/129 (93.8%) streptococci and 63/70 (90.0%) enterococci. Excellent results were obtained for S. pneumoniae (45/45) and beta-hemolytic streptococci (49/50). With regard to viridans streptococci, the accuracy of the Phoenix system was 83.9%. Among the latter organisms, the best performance was obtained with isolates of the Streptococcus sanguinis group and Streptococcus anginosus group; problems were instead encountered with the Streptococcus mitis group. Four E. faecium and three E. faecalis isolates were misidentified as Enterococcus casseliflavus/Enterococcus gallinarum or Enterococcus durans. Thus, these isolates were identified only at the genus level. Compared with commercially available systems, the Phoenix system appears a reliable diagnostic tool for identifying clinically relevant streptococci and enterococci. The SMIC/ID-2 panel proved particularly effective for beta-hemolytic streptococci and pneumococci.
authors.affiliation: Laboratory of Medical Microbiology, University of Insubria and Ospedale di Circolo e Fondazione Macchi, Viale Borri 57, 21100, Varese, Italy.
authors.forename: Gioconda
authors.initials: G
authors.lastname: Brigante
authors.forename: Francesco
authors.initials: F
authors.lastname: Luzzaro
authors.forename: Alessia
authors.initials: A
authors.lastname: Bettaccini
authors.forename: Gianluigi
authors.initials: G
authors.lastname: Lombardi
authors.forename: Francesca
authors.initials: F
authors.lastname: Meacci
authors.forename: Beatrice
authors.initials: B
authors.lastname: Pini
authors.forename: Stefania
authors.initials: S
authors.lastname: Stefani
authors.forename: Antonio
authors.initials: A
authors.lastname: Toniolo
mesh_terms: D001331:Automation; D001426:Bacterial Proteins / Q000235:genetics; D015373:Bacterial Typing Techniques / Q000295:instrumentation / Q000379:methods; D019411:Clinical Laboratory Techniques; D016983:Enterococcus / Q000145:classification* / Q000235:genetics; D006801:Humans; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D011933:Reagent Kits, Diagnostic; D012680:Sensitivity and Specificity; D017422:Sequence Analysis, DNA; D013045:Species Specificity; D013291:Streptococcus / Q000145:classification* / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D012336:RNA, Ribosomal, 16S; D011933:Reagent Kits, Diagnostic