Direct Bacterial Identification in Positive Blood Cultures by Use of Two Commercial Matrix-Assisted Laser Desorption Ionization–Time of Flight Mass Spectrometry Systems

Abstract

. Overall, the Biotyper system generated significantly more accurate identifications than the Vitek MS IVD system (P ‫؍‬ 0.016; 177 versus 167 out of 181 specimens). The Biotyper system identified the minority species among polymicrobial blood cultures. We also compared the performance of an in-house extraction method with that of the Sepsityper on both MALDI-TOF MS systems. The in-house method generated more correct identifications at the genus level than the Sepsityper (96.7% versus 93.5%) on the Biotyper system, whereas the two methods exhibited the same performance level (88.0% versus 88.0%) on the Vitek MS IVD system. Our study confirmed the practical advantages of MALDI-TOF MS, and our in-house extraction method reduced the reagent cost to $1 per specimen, with a shorter turnaround time of 3 h, which is highly cost-effective for a diagnostic microbiology service. Bloodstream infection is a condition associated with high morbidity and mortality (1, 2). The rapid identification of bloodstream pathogens is critical to clinical management and the choice of appropriate antibiotic treatments (3, 4). Currently, microbiologic diagnosis of bacteremia relies on subculture of positive blood culture broths on solid medium for an 18-to 24-h incubation period followed by biochemical tests or an automated preformed enzyme assay for identification of the bacteria (5). In general, laboratory diagnosis of common pathogens requires 18 to 48 h, while diagnosis of fastidious organisms requires longer incubation and identification procedures. Although the use of modern techniques such as fluorescence in situ hybridization and PCR can shorten the identification time (6), these operations require specialized equipment and technical expertise and the targeted pathogens are limited in a single run (7). Therefore, the introduction of a simple, rapid, broad-spectrum, and cost-effective system for the identification of blood culture pathogens is imperative.Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) was developed in the 1980s, and this technique had been widely used for biomolecule analysis in the chemical industry for over 10 years. In recent years, MALDI-TOF MS was introduced for bacterial identification, which revolutionized the diagnostic microbiology service (8). Two manufacturers, bioMérieux (Marcy l'Etoile, France) and Bruker Daltonics (Bremen, Germany), are marketing efficient MALDI-TOF systems, the Vitek-MS and the Microflex LT, respectively, that allow the identification of bacteria and yeasts in a few minutes instead of the hours required by traditional methods. The practical use of MALDI-TOF MS for microorganism identification directly from positive blood culture specimens has been substantiated by a number of studies (9-13). Generally, studies have shown high identification rates for various types of organisms with the use of MALDI-TOF MS . However, various organism isolation methods from blood were used in those studies and therefore method standardization is necessary. The...

Bloodstream Infections

“…Procalcitonin and C-reactive protein are already in use widely but the search is on for even better agents. The performance of soluble triggering receptor expressed on myeloid cells-I (sTREM-1), soluble urokinasetype plasminogen receptor (suPAR), proadrenomedullin (pro ADM), and presepsin appears promising and offers better prognostic performance than procalcitonin [10,11]. The use of biomarkers in sepsis has been discussed in this special issue.…”

Comparative Evaluation of the Bruker Biotyper and Vitek MS Matrix-Assisted Laser Desorption Ionization–Time Of Flight (MALDI-TOF) Mass Spectrometry Systems for Identification of Yeasts of Medical Importance

“…To date, four MALDI-TOF MS systems are commercially available: the Microflex LT Biotyper (Bruker Daltonics, Bremen, Germany) (BMS), the Saramis system (bio-Mérieux, Marcy l'Etoile, France), the Vitek MS system (bioMérieux, Marcy l'Etoile, France) (VMS), and, very recently, the Andromas system (Andromas, Paris, France). Several comparative studies have already been performed using the most common systems (BMS and VMS), but, to the best of our knowledge, they have focused only on the identification of bacteria (10)(11)(12)(13). Only very recently was a comparative study on yeasts performed using BMS and Saramis (bio-Mérieux, Marcy l'Etoile, France), the previously distributed version of VMS (14).…”

Identifying microbes from environment water samples in a discovery-based learning module

“…1,[15][16][17] This is demonstrated by increasing adoption of the technique in both research and clinical laboratories. 18,19 Unfortunately, the situation is not mirrored on the education front where the focus remains on conventional identification techniques, with lack of coverage of emerging methods such as mass spectrometric profiling of biomarkers that identify specific species. Driven by the desire to help fill the curriculum gap, I developed an inquiry-based education activity ( Figure 1) to introduce students to a leading edge mass spectrometry microbe identification technique (i.e., matrix assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS), (Ng, 2013) 20 where students gain practical and theoretical knowledge of the analytical instrument and associated bioinformatics tools, while employing the scientific method in solving a real world problem with unknown answers: what are the microbes present in an environment water sample?…”