839. Lack of Evidence for Toxin Immunoassay-Negative Patients as a Significant Source of Clostridium difficile Transmission at an Academic Medical Center
Session: Oral Abstract Session: Clostridium difficile
Thursday, October 27, 2016: 2:15 PM
Room: 388-390
Background: Clostridium difficile is a major cause of healthcare-associated infection but the sources of transmission in hospitalized patients are poorly understood. Patients with fecal toxin-positive C. difficile infection (CDI) are a known source of transmission in hospitals. However, the role of patients with diarrheal symptoms who are fecal toxin-negative by immunoassay but C. difficile positive by PCR or culture (i.e., Tox-/C. difficile+) is unknown and important for hospitals using toxin tests for diagnosis.

Methods: Hospitalized adults with positive and negative clinical toxin immunoassay test results had C. difficileisolated by culture over 4 months and analyzed for genetic relatedness by PCR ribotyping and whole genome sequence characterization of single nucleotide polymorphisms (SNP). Toxin results were used to discontinue contact precautions in negative patients. Positive results (toxin and culture) were classified as incident or recurrent and community onset (CO) or hospital onset (HO) CDI events using NHSN LabID rules.

Results: There were 98 NHSN LabID CDI events in 93 patients of which 85/98 (86.7%) had an isolate analyzed for relatedness. Using a strict 0-2 SNP definition for relatedness, only 2 of 39 (5.1%) HO-CDI events analyzed were related to another CDI event in the cohort (1 CO-CDI, 1 recurrent CDI). Higher rates of relatedness were observed among CO-CDI events (7 of 36 (19.4%)) due to previous CDI episodes and shared healthcare facility exposures. Five of eight 0-2 SNP pairings implicated a Tox-/C. difficile+ patient in a possible forward or horizontal transmission event but all five required transmission across non-overlapping hospitalizations and locations or transmission to patients with previous CDI episodes making them epidemiologically less likely.

Conclusion: Few HO-CDI patients had a C. difficile strain related to another symptomatic CDI patient in this study despite inclusion of Tox-/C. difficile+ patients with diarrhea. Horizontal transmission between symptomatic CDI patients may be an uncommon source of new CDI cases in hospitals with active infection prevention programs. More studies are needed to verify these findings and identify other sources of CDI such as transmission from asymptomatic C. difficile carriers and endogenous colonization.

Christopher Polage, MD1, Maria Sjolund-Karlsson, PhD2, Christopher Gulvik, PhD2, David Eyre, BM BCh DPhil MCRP FRCPath3, Clare Gyorke, BS4, Michael Kennedy, BS5, Stuart H. Cohen, MD, FIDSA, FSHEA, FACP6, Erik R. Dubberke, MD, MSPH, FIDSA, FSHEA7, L. Clifford Mcdonald, MD, FSHEA2 and Brandi Limbago, PhD8, (1)Pathology and Infectious Diseases, University of California, Davis Medical Center, Sacramento, CA, (2)Centers for Disease Control and Prevention, Atlanta, GA, (3)Nuffield Department of Medicine, University of Oxford, Oxford, United Kingdom, (4)University of California, Davis Medical Center, Sacramento, CA, (5)Pathology and Laboratory Medicine, University of California, Davis School of Medicine, Sacramento, CA, (6)Internal Medicine, University of California, Davis Medical Center, Sacramento, CA, (7)Washington University School of Medicine, St. Louis, MO, (8)Centers for Disease Control and Prevention, National Center for Emerging and Zoonotic Infectious Diseases, Division of Healthcare Quality Promotion, Atlanta, GA


C. Polage, None

M. Sjolund-Karlsson, None

C. Gulvik, None

D. Eyre, None

C. Gyorke, None

M. Kennedy, None

S. H. Cohen, None

E. R. Dubberke, Rebiotix Inc.: Investigator and Scientific Advisor , Consulting fee and Research support
Merck: Consultant and Investigator , Consulting fee and Research support
Sanofi Pasteur: Consultant and Grant Investigator , Consulting fee and Grant recipient
Summitt: Consultant , Consulting fee

L. C. Mcdonald, None

B. Limbago, None

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