Performance evaluation of the BD phoenix automated microbiology system in meropenem susceptibility testing of clinical Pseudomonas aeruginosa isolates.

I the management of pseudomonal infections, carbapenems are among the most potent and the last-line of antibiotics. Therefore, reliable in vitro susceptibility testing of the clinical isolates of Pseudomonas aeruginosa (P. aeruginosa) against carbapenems is of paramount importance for the healthcare outcome.1 However, in the post-market evaluations, it has been demonstrated that not all the testing systems produce universally accurate results for carbapenems.2 There is a trend for the use of the new generation technology platforms to achieve a shorter turn around time in identification and susceptibility testing. The Phoenix Automated Microbiology System (AMS) (BD Diagnostic Systems, Sparks, MD) is a fully automated new technology platform for rapid identification (ID) and antimicrobial susceptibility testing (AST) of grampositive and gram-negative bacteria.3 The aim of the present study was, to compare the performance of the routinely used standard disk diffusion method (SDM) and the BD Phoenix AMS (BD Diagnostic Systems, Sparks, MD) for the determination of meropenem susceptibility in the clinical isolates of P. aeruginosa. The study was conducted on 142 non-repetitive clinical isolates of P. aeruginosa. The isolates were selected from a collection of isolates obtained from those patients admitted to the University Hospital Ondokuz Mayis, between July and December 2003. For isolate selection, the criteria described in the Class II Special Controls Guidance Document for antimicrobial susceptibility test systems (FDA-CII/ AST) published by the Food and Drug Administration (FDA) Office of In Vitro Diagnostic Device Evaluation and Safety4 have been modified. The modification was to adjust the ratio of meropenem susceptible, intermediate, and resistant isolates approximately to 42%, 9% and 49%, based on the AST results with the standard broth microdilution (SBM) method. Organism identification and Phoenix AST. The strain definition for P. aeruginosa was as follows: oxidase positive, catalase positive, pigment