Direct inoculation method for identification and antimicrobial susceptibility testing using matrix-assisted laser desorption ionization-time of flight mass spectrometry and both the Vitek 2 and MicroScan Walkaway 96 Plus systems. Issue 3 (4th May 2023)

• Record Type: Journal Article
• Authors: Brandt, Maryann; McCullor, Kimberly; Harris, Don; Ratzlaff, Zachary; Thompson, Eric; Pfeifer, Cory M.
• Is Part Of: Proceedings. Volume 36:Issue 3(2023)
• Page Start: 354
• Page End: 359
• Publication Date: 2023-05-04
• Subjects: Antimicrobial susceptibility testing -- clinical microbiology; Medicine -- Periodicals; Medicine; Medicine -- Periodicals; Periodicals; Electronic journals; 616.005
• DOI: 10.1080/08998280.2023.2169556
• Languages: English
• ISSNs: 0899-8280

Abstract

Abstract: The aim of our study was to evaluate a protocol utilizing serum separator tubes (SST) to facilitate a faster, cost-effective, direct method for rapid sensitivity testing and identification of positive blood cultures. Spiked cultures were inoculated into either Becton Dickinson (BD) BACTEC TM Aerobic Plus or Anaerobic/F bottles containing sterile human blood. Bottles were immediately processed when positive. A parallel study using patient isolates was used in which bacteria were pelleted by SST from positive blood cultures. For identification, a portion of the pellet was tested by matrix-assisted laser desorption/ionization as described by the manufacturer. MicroScan panels and Vitek 2 results were compared. Categorical agreement was used as comparison to standard subculture and/or polymerase chain reaction methods. No discordant identifications were observed, and 86% generated a successful identification when compared to subculture methods. For the Vitek 2, we observed a 99% essential agreement when compared to the subculture method. For the MicroScan Walkaway, we observed 94.9%, 97.4%, and 100% categorical agreement for MIC panels 53, 38, and MICroSTREP Plus 2, respectively. Turnaround times were reduced from 4 hours for identification and 11 hours for antimicrobial sensitivity testing. We conclude that the SST method results in timelier, actionable results for antimicrobial stewardship initiatives.