Affiliation:
1. Laboratory of Medical Microbiology, Ospedale di Circolo and University of Insubria, Varese
2. Department of Molecular Biology, University of Siena, Siena
3. Department of Microbiological Sciences, University of Catania, Catania, Italy
Abstract
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'Étoile, 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.
Publisher
American Society for Microbiology
Cited by
28 articles.
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