Comparative Analysis of PCR–Electrospray Ionization/Mass Spectrometry (MS) and MALDI-TOF/MS for the Identification of Bacteria and Yeast from Positive Blood Culture Bottles

Abstract

BACKGROUND Emerging technologies for rapid identification of microbes demonstrate a shift from traditional biochemical and molecular testing algorithms toward methods using mass spectrometry (MS) for the semiquantitative analysis of microbial proteins and genetic elements. This study was performed to assess the diagnostic accuracy of 2 such technologies, PCR–electrospray ionization (ESI)/MS and MALDI-TOF/MS, with respect to phenotypic and biochemical profiling as a reference standard method. A positive challenge set of blood culture bottles was used to compare PCR-ESI/MS and MALDI-TOF/MS performance on a matched set of samples. METHODS We performed characterization of bloodstream infections from blood cultures using the Ibis T5000 PCR-ESI/MS and the Bruker MALDI Biotyper 2.0 (MALDI-TOF/MS) platforms for microbial identification. Diagnostic accuracy was determined by independent comparison of each method to phenotypic and biochemical characterization with Vitek2 analysis as the reference standard identification. RESULTS The diagnostic accuracy, represented as positive agreement, at the genus level was 0.965 (0.930–0.984) for PCR-ESI/MS and 0.969 (0.935–0.987) for MALDI-TOF/MS, and at the species level was 0.952 (0.912–0.974) with PCR-ESI/MS and 0.943 (0.902–0.968) for MALDI-TOF/MS. No statistically significant difference was found between PCR-ESI/MS and MALDI-TOF/MS in the ability to rapidly identify microorganisms isolated from blood culture. CONCLUSIONS Our results demonstrate that PCR-ESI/MS and MALDI-TOF/MS are equivalent in their ability to characterize bloodstream infections with respect to the reference standard, and highlight key differences in the methods that allow for each method to have a unique niche as a tool for rapid identification of microbes in blood cultures.

Detection, Identification, and Distribution of Fungi in Bronchoalveolar Lavage Specimens by Use of Multilocus PCR Coupled with Electrospray Ionization/Mass Spectrometry

“…The PCR/ESI-MS technique has many attractive features compared with conventional culture methods and organism-specific PCR (9,21,22). It not only possesses enough sensitivity to detect pathogens directly in clinical specimens (10, 13) but also has precise discriminatory powers to simultaneously differentiate several pathogen species in a single specimen.…”

“…This result was not surprising in this study, because many nonpathogenic fungi can colonize the respiratory tract. These results can be interpreted as false-positive results because the PCR/ESI-MS method can detect nonviable or contaminated fungal DNA introduced during the handling of specimens (9). It was noticed that PCR/ESI-MS also provided quantitative results for each target; whether this DNA load information facilitates the data analysis and interpretation will require further investigation.…”

“…This method enables detection and identification of causative pathogens directly from clinical specimens or mixtures of organisms with rapid turnaround and high throughput (9,10). This technique has been used to detect bacteria, viruses, yeasts, and other infectious agents (10)(11)(12)(13), but there are no data on its value for the detection of fungal organisms, including yeasts and molds.…”

Enhanced Diagnostic Yields of Bacteremia and Candidemia in Blood Specimens by PCR-Electrospray Ionization Mass Spectrometry

“…Samples for molecular analysis were analyzed using the BAC Spectrum assay (Ibis Biosciences) on the PCR-ESI-MS system (PLEX-ID; Abbott Laboratories), as described previously (17,(21)(22)(23). The details of the primer sequences, gene targets, primer coverage of the bacterial and fungal domains, and the organization and multiplexing configuration of the primers on the microtiter plates are described in Table S1 in the supplemental material.…”

In vitro diagnosis of sepsis: a review

“…The turnaround is ∼4-6 hours after positive BC, 97 and this assay permits analysis of six samples a time. 98 This platform shows high analytical accuracy in comparison to routine subculture of BC bottles. 96,99 A major advantage of this method is the ability to characterize an organism without previous knowledge and to analyze mixtures of microbes directly from raw BC broth without the need for separation of colonies by subculturing.…”