Downloaded from http://journals.lww.com/shockjournal by BhDMf5ePHKbH4TTImqenVIu1/FN/J4kOKR5ilJ/zjjoQMvkN0OnujwfR1Xk3tCr3 on 04/09/2020 PLASMA BACTERIAL AND MITOCHONDRIAL DNA DISTINGUISH BACTERIAL SEPSIS FROM STERILE SYSTEMIC INFLAMMATORY RESPONSE SYNDROME AND QUANTIFY INFLAMMATORY TISSUE INJURY IN NONHUMAN PRIMATES Tolga Sursal,* Deborah J. Stearns-Kurosawa, † Kiyoshi Itagaki,* Sun-Young Oh, † Shiqin Sun,* Shinichiro Kurosawa, † and Carl J. Hauser* *Department of Surgery, Beth Israel Deaconess Medical Center; † Department of Pathology and Laboratory Medicine, Boston University School of Medicine, Boston, MA Received 12 Jul 2012; first review completed 30 Jul 2012; accepted in final form 1 Oct 2012 ABSTRACT—Systemic inflammatory response syndrome (SIRS) is a fundamental host response common to bacterial infection and sterile tissue injury. Systemic inflammatory response syndrome can cause organ dysfunction and death, but its mechanisms are incompletely understood. Moreover, SIRS can progress to organ failure or death despite being sterile or after control of the inciting infection. Biomarkers discriminating between sepsis, sterile SIRS, and postinfective SIRS would therefore help direct care. Circulating mitochondrial DNA (mtDNA) is a damage-associated molecular pattern reflecting cellular injury. Circulating bacterial 16S DNA (bDNA) is a pathogen-associated pattern (PAMP) reflecting ongoing infec- tion. We developed quantitative polymerase chain reaction assays to quantify these markers, and predicting their plasma levels might help distinguish sterile injury from infection. To study these events in primates, we assayed banked serum from Papio baboons that had undergone a brief challenge of intravenous Bacillus anthracis delta Sterne (modified to remove toxins) followed by antibiotics (anthrax) that causes organ failure and death. To investigate the progression of sepsis to ‘‘severe’’ sepsis and death, we studied animals where anthrax was pretreated with drotrecogin alfa (activated protein C), which attenuates sepsis in baboons. We also contrasted lethal anthrax bacteremia against nonlethal E. coli bacteremia and against sterile tissue injury from Shiga-like toxin 1. Bacterial DNA and mtDNA levels in timed samples were correlated with blood culture results and assays of organ function. Sterile injury by Shiga-like toxin 1 increased mtDNA, but bDNA was undetectable: consistent with the absence of infection. The bacterial challenges caused parallel early bDNA and mtDNA increases, but bDNA detected pathogens even after bacteria were undetectable by culture. Sublethal E. coli challenge only caused transient rises in mtDNA consistent with a self-limited injury. In lethal anthrax challenge (n = 4), bDNA increased transiently, but mtDNA levels remained elevated until death, consistent with persistent septic tissue damage after bacte- rial clearance. Critically, activated protein C pretreatment (n = 4) allowed mtDNA levels to decay after bacterial clearance with sparing of organ function and survival. In summary, host tissue injury correlates with mtDNA whether infective or sterile. Mitochondrial DNA and bDNA polymerase chain reactions can quantify tissue injury incurred by septic or sterile mechanisms and suggest the source of SIRS of unknown origin. KEYWORDS—Sepsis, inflammation, bacteremia, systemic inflammatory response syndrome, trauma INTRODUCTION The systemic inflammatory response syndrome (SIRS) can occur either in the setting of sepsis due to pathogens or in a wide variety of circumstances where sterile processes activate inflammation. Both types of initiating events signal Bdanger[ to the immune system. In terms of molecular pathogenesis, however, sterile SIRS reflects activation of innate immune pathways by host damage-associated molecular patterns (DAMPs) (1), whereas sepsis is initiated by pathogen-associated molec- ular patterns (PAMPs) originating from infecting organisms (2). Sepsis and SIRS activate immunity through similar (or identical) pattern recognition receptors, but distinguishing between them clinically is critical, perhaps most obviously because empiric use of antibiotics encourages the emergence of resistant bacteria. The sharing of cellular pathways by which DAMPs and PAMPs act can cause the downstream immune responses to sepsis and SIRS to be indistinguishable. Thus, clinical re- sponses to infective and noninfective challenge may also be similar (3). Current clinical practice relies on laboratory tests and clinical judgment to distinguish between sterile SIRS and sepsis due to pathogens. Cultures diagnostic of infection typically take days to grow out, limiting their value. More- over, in many cases, bacterial isolates only reflect colo- nization. Last, infective and noninfective inflammation can 55 SHOCK, Vol. 39, No. 1, pp. 55Y62, 2013 Address inquiries to Carl J. Hauser, MD, Department of Surgery, Beth Israel Deaconess Medical Center, 330 Brookline Ave, Boston, MA 02215. E-mail: cjhauser@bidmc.harvard.edu; or Shinichiro Kurosawa, MD, Department of Pathology and Laboratory Medicine, Boston University School of Medicine, 670 Albany St, Boston, MA 02118. E-mail: kurosawa@bu.edu. T.S. and D.J.S.-K. are coYfirst authors. S.Y.-O. is now with the Global Process Systems, Buson, Korea; S.S. is now with the College of Pharmacy, Harbin Medical University, Daqing, China. This work was supported by National Institutes of Health/National Institute of General Medical Sciences grant R01 GM089711 and Department of Defense CDMRP/DRMRP hypothesis development award DR080924 (to C.J.H.) and by National Institutes of Health/National Institute of Allergy and Infectious Diseases grants RO1 AI058107, UO1 AI1075386, and U19 AI062629 (to S.K.). The authors have no conflicts of interest to declare. Supplemental digital content is available for this article. Direct URL citation appears in the printed text and is provided in the HTML and PDF versions of this article on the journal_s Web site (www.shockjournal.com). DOI: 10.1097/SHK.0b013e318276f4ca Copyright Ó 2013 by the Shock Society Copyright © 2012 by the Shock Society. Unauthorized reproduction of this article is prohibited.