Simultaneous Immunodetection of Anthrax, Plague, and Tularemia from Blood Cultures by Use of Multiplexed Suspension Arrays

Abstract

Multiplexed detection technologies are becoming increasingly important given the possibility of bioterrorism attacks, for which the range of suspected pathogens can vary considerably. In this work, we describe the use of Luminex MagPlex magnetic microspheres for the construction of two multiplexed diagnostic suspension arrays, enabling antibody-based detection of bacterial pathogens and their related disease biomarkers directly from blood cultures. The first 4-plex diagnostic array enabled the detection of both anthrax and plague infections using soluble disease biomarkers, including protective antigen (PA) and anthrax capsular antigen for anthrax detection and the capsular F1 and LcrV antigens for plague detection. The limits of detection (LODs) ranged between 0.5 and 5 ng/ml for the different antigens. The second 2-plex diagnostic array facilitated the detection of Yersinia pestis (LOD of 1 × 10⁶ CFU/ml) and Francisella tularensis (LOD of 1 × 10⁴ CFU/ml) from blood cultures. Inoculated, propagated blood cultures were processed (15 to 20 min) via 2 possible methodologies (Vacutainer or a simple centrifugation step), allowing the direct detection of bacteria in each sample, and the entire assay could be performed in 90 min. While detection of bacteria and soluble markers from blood cultures using PCR Luminex suspension arrays has been widely described, to our knowledge, this study is the first to demonstrate the utility of the Luminex system for the immunodetection of both bacteria and soluble markers directly from blood cultures. Targeting both the bacterial pathogens as well as two different disease biomarkers for each infection, we demonstrated the benefit of the multiplexed developed assays for enhanced, reliable detection. The presented arrays could easily be expanded to include antibodies for the detection of other pathogens of interest in hospitals or labs, demonstrating the applicability of this technology for the accurate detection and confirmation of a wide range of potential select agents.

Keywords: anthrax; blood culture; immunodetection; magnetic beads; multiplex; plague; tularemia.