Pleomorphic Structures in Human Blood Are Red Blood Cell-Derived Microparticles, Not Bacteria

• Type of Material: Article
• Authors: Adam Mitchell, Emory University; Warren D. Gray, Emory University; Max Schroeder, Emory University; Hong Yi, Emory University; Jeannette V. Taylor, Emory University; Rebecca S. Dillard, Emory University; Zunlong Ke, Georgia Institute of Technology; Elizabeth Wright, Emory University; David Stephens, Emory University; John Roback, Emory University; Charles Searles Jr, Emory University
• Language: English
• Date: 2016-10-19
• Publisher: Public Library of Science
• Publication Version: Final Published Version
• Copyright Statement: © 2016 Mitchell et al.
• License: Creative Commons Attribution 4.0 International
• Final Published Version (URL): http://dx.doi.org/10.1371/journal.pone.0163582
• Title of Journal or Parent Work: PLoS ONE
• ISSN: 1932-6203
• Volume: 11
• Issue: 10
• Start Page: e0163582
• End Page: e0163582
• Grant/Funding Information: This work was supported by the National Institutes of Health (R01HL109559, R01HL124879, R01HL095476, S10RR025679), and a VA Merit Award (I01 BX000704). Research reported in this publication was also supported by the National Heart, Lung, and Blood Institute of the National Institutes of Health under Award Number T32HL007745.; The JEOL JEM-2200FS transmission electron microscope was acquired with an NSF-MRI grant (0923395).; The JEOL JEM-1400 transmission electron microscope was acquired with an NIH S10 grant (S10RR025679).
• Keywords: Polymerase chain reaction; Transmission electron microscopy; Science & Technology; DNA isolation; Blood transfusion; Blood; Multidisciplinary Sciences; Flow cytometry; MICROSCOPY; NANOBACTERIA; Vesicles; Bacteria
• Research Categories: Health Sciences, Pathology; Health Sciences, Medicine and Surgery

Abstract

Background: Red blood cell (RBC) transfusions are a common, life-saving therapy for many patients, but they have also been associated with poor clinical outcomes. We identified unusual, pleomorphic structures in human RBC transfusion units by negative-stain electron microscopy that appeared identical to those previously reported to be bacteria in healthy human blood samples. The presence of viable, replicating bacteria in stored blood could explain poor outcomes in transfusion recipients and have major implications for transfusion medicine. Here, we investigated the possibility that these structures were bacteria. Results: Flow cytometry, miRNA analysis, protein analysis, and additional electron microscopy studies strongly indicated that the pleomorphic structures in the supernatant of stored RBCs were RBC-derived microparticles (RMPs). Bacterial 16S rDNA PCR amplified from these samples were sequenced and was found to be highly similar to species that are known to commonly contaminate laboratory reagents. Conclusions: These studies suggest that pleomorphic structures identified in human blood are RMPs and not bacteria, and they provide an example in which laboratory contaminants may can mislead investigators.