Abstract
Rapid identification of microorganisms from positive blood cultures has improved clinical management and antimicrobial stewardship. The advent of matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) has reduced the time to identification of cultured isolates and is now often the definitive method used in the clinical microbiology laboratory. The commercial in vitro diagnostic MALDI Sepsityper (Sepsityper) kit has the potential for standardization and clinical routine use for the rapid identification of a broad range of bacteria from positive blood cultures. In this study, we performed a parallel evaluation of the Sepsityper (Bruker Daltonics, Billerica, MA) and the Verigene BC-GN (BC-GN) assays (Nanosphere, Inc., Northfield, IL) for the identification of Gram-negative bacilli. A total of 210 Bactec bottles demonstrating Gram-negative bacilli were prospectively enrolled for this study. Among these, 200 monomicrobial cultures were included in the comparative analysis. For monomicrobial cultures, the BC-GN detected 85% (170/200) compared to that detected by routine culture while the Sepsityper detected 94% (188/200) and 91% (181/200) to the genus and species levels, respectively. Comparable positive percentage agreement and negative percentage agreement were observed between the Sepsityper (96.5% and 98.8%, respectively) and the BC-GN (99.4% and 99.8%, respectively) when only (n = 170, 85%) organisms targeted by the latter test were included in the analysis. In conclusion, the two methods evaluated in this study showed excellent performance characteristics for the identification of Gram-negative bacilli commonly isolated from blood cultures. The Sepsityper showed a broader identification range capability that may further improve clinical management and antimicrobial stewardship in patients with less frequent Gram-negative bacilli bloodstream infections.