[Evaluation of the Phoenix system for identifying and determining the susceptibility of clinical isolates....

The Phoenix system (BD Diagnostic Systems), a rapid ID/AST system, was compared with the MicroScan WalkAway-40 system for accuracy of identification and antimicrobial susceptibility test results. The 327 bacterial isolates, were comprised of 191 Gram-negative bacilli (187 Enterobacteriaceae and 4 Aeromonas spp.) and 136 Gram-positive cocci (27 Staphylococcus aureus, 53 coagulase-negative staphylococci, 45 enterococci and 11 beta haemolytic streptococci). The overall rate of agreement between the two systems for species level identification was 95.8% and 96.3% for Gram-negative bacilli and Gram-positive cocci, respectively. Enterococcus and Streptococcus species both achieved a 100% rate of species level agreement. The genus level agreement was >99% overall. Arbitration of the 8 Gram-negative bacilli disagreements resolved with 7 in agreement with the Phoenix identification. For the 5 Gram-positive cocci disagreements, 3 resolved in agreement with Phoenix. Overall, 3688 antimicrobial/organism combinations were evaluated in both systems. For Gram-negative isolates, the rate of essential agreement for the MICs was 98.5%, while the categorical agreement rate was 95.9%. Arbitration of 13 Gram-negative disagreements resolved with 11 in agreement with the Phoenix system. For Staphylococcus spp. and Enterococcus spp. isolates, the essential agreement rates were 96.4% and 99% respectively. Categorical agreement rates for both genera were 94.7% and 96.1%, respectively. Arbitration of 5 staphylococci disagreements resolved with 2 in agreement with Phoenix system. Our results show that the Phoenix system is a rapid and reliable system for both identification and antimicrobial susceptibility testing of common clinical isolates.