Evaluation of the BD Phoenix automated identification and susceptibility testing system in clinical microbiology laboratory practice

The Phoenix Automated Microbiology System (BD Biosciences, USA) is a new, fully automated system for the rapid identification and antimicrobial susceptibility testing of gram-positive and gram-negative bacteria. The objective of this study was to evaluate the quality of performance of the Phoenix system in the identification and antimicrobial susceptibility testing of 260 gram-negative (n=174) and gram-positive (n=86) isolates collected from Polish hospitals in recent years. Two Phoenix panel types for identification/antimicrobial susceptibility testing, NMIC/ID-5 for gram-negative rods and PMIC/ID-4 for gram-positive cocci, were used in the analysis according to the manufacturer's recommendations. The results produced by the system were compared with data obtained by reference or conventional microbiological methods. A high rate of agreement between the Phoenix and the conventional methods was observed for identification, ranging from 100% for gram-positive cocci to 96.0% for gram-negative nonfermenters and 92.5% for members of the family Enterobacteriaceae. Similarly, a high level of agreement characterized the antimicrobial susceptibility data obtained with the Phoenix and by the agar dilution method (2,361 test results). For staphylococci, enterococci and Enterobacteriaceae, the methods were 100% concordant in determining the category of susceptibility of isolates to the majority of the antimicrobial agents tested. A category agreement value of below 90% was found for the susceptibility of enterococci and gram-negative nonfermenters to ciprofloxacin (84.6% and 88.5%, respectively) and for susceptibility of Stenotrophomonas maltophilia to trimethoprim-sulfamethoxazole (80.0%).