Optimized Use of the MALDI BioTyper System and the FilmArray BCID Panel for Direct Identification of Microbial Pathogens from Positive Blood Cultures

Abstract

The rapid detection and/or identification (ID) of the microbial pathogens responsible for bloodstream infections (BSIs) is pivotal for reducing infection-related mortality and costs (1), particularly for severely ill patients (2, 3). Although blood culture (BC) continues to be essential for BSI diagnosis, the turnaround time for ID can be accelerated using new technologies that are directly applied to positive BC bottles/broths (4).Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) was recently demonstrated to improve the clinical management of BSIs (5, 6) and allow patients to receive appropriate antimicrobial therapy earlier (i.e., 24 h from the first positive BC) (7). However, despite its well-documented good performance (8-17), this method often fails to identify polymicrobial BCs in their entirety.Another method is the multiplex PCR-based FilmArray blood culture ID (BCID) panel (bioMérieux, Marcy l'Etoile, France), which is equally as fast as the MALDI-TOF MS (e.g., MALDI BioTyper system [Bruker Daltonics, Bremen, Germany]). This technique was developed for the simultaneous identification of 24 microbial pathogens, including 19 bacterial genera/species and 5 Candida species (and 3 antibiotic resistance determinants). In addition to its high sensitivity and specificity, the FilmArray BCID panel has proven to be accurate for identifying not only monomicrobial but also polymicrobial . Notably, successful results were obtained with BC broths tested before the bottles became positive or even before the bottles were incubated in the BC instrument as usual (24). To date, the extensive use of the FilmArray BCID panel in routine clinical laboratory practice has been hampered by the high cost of reagents/consumables.In this study, we developed a BSI diagnostic algorithm that relied on the direct analysis of positive BC bottles/broths using the MALDI BioTyper system supplemented with the FilmArray BCID panel. We evaluated this algorithm in terms of ID accuracy and turnaround time by comparing the results with a reference culture-based procedure.(This work has been presented in part as a poster at the 24th European Congress of Clinical Microbiology and Infectious Diseases, 10 to 13 May 2014, Barcelona, Spain).

A rapid diagnostic workflow for cefotaxime-resistant Escherichia coli and Klebsiella pneumoniae detection from blood cultures by MALDI-TOF mass spectrometry

“…MALDI-TOF MS analyses were performed using a Microflex LT mass spectrometer (Bruker Daltonics, Bremen, Germany). Spectra were analyzed with the Bruker’s Biotyper software (version 3.1), and the Bruker Biotyper library V.4.0.0.1 (5627 entries) was used to achieve bacterial identification [ 13 ]. BC samples that were found to contain E .…”

“…In contrast, molecular genetic methods are timely but able to only provide information about the absence or presence of an ESBL gene, which not always correlates to the phenotype [ 11 ]. Reasonably, matrix-assisted laser desorption ionization–time of flight mass spectrometry (MALDI-TOF MS), that is used for successful microbe identification [ 12 ], also direct from positive blood cultures (BCs) [ 13 ], in many clinical laboratories, has been explored as a tool for rapid antimicrobial resistance detection [ 14 ]. In one of these newly generated assays [ 15 ], enzymatic cleavage of the β-lactam ring (in the β-lactam antibiotic) leads to specific mass shifts that can be easily monitored by MALDI-TOF MS.…”

Characterization of microbial mixtures by mass spectrometry

“…222 Identification of constituent microbes in mixtures containing both bacteria and yeasts failed in one study. 224 Another recent study noted a higher (3×) error rate with polymicrobial cultures than with monomicrobial ones. 228 Such poor performance has led some to conclude that MALDI-based characterization of polymicrobial cultures in the clinical microbiology lab is not reliable.…”

“…Rates of correct identification of one isolate in mixtures have ranged from 46% to 93% . Identification of constituent microbes in mixtures containing both bacteria and yeasts failed in one study . Another recent study noted a higher (3×) error rate with polymicrobial cultures than with monomicrobial ones .…”

Simplified Testing Method for Direct Detection of Carbapenemase-Producing Organisms from Positive Blood Cultures Using the NG-Test Carba 5 Assay

“…Bottles were incubated until they signaled positive by the BacT/Alert Virtuo system (bioMérieux), with bacterial concentrations ranging from 2 ϫ 10 7 to 6 ϫ 10 9 CFU/ml. Second, we included 310 consecutively positive BCs from nonduplicate patients that grew K. pneumoniae organisms ( Table 2), as identified by matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry-based diagnostic workflow (9). By this workflow, we subjected positive-BC bottle broth aliquots to direct analysis with the MALDI Biotyper system (Bruker Daltonics, Bremen, Germany) for species-level identification.…”