526. Etiology Unknown: Are Less Recognized Respiratory Pathogens Associated with a Milder Course of Illness?
Session: Poster Abstract Session: Respiratory Infections: Viral (non Influenza)
Thursday, October 8, 2015
Room: Poster Hall
  • 526_PanNegative.pdf (357.0 kB)
  • Background: Multiplex assays have greatly enhanced the etiologic determination of acute respiratory infection (ARI). Yet ~40% of ARI in the multiplex era are test-negative, suggesting that less recognized pathogens account for a significant proportion of illnesses. Evaluating the demographic and clinical characteristics of patients with unknown etiology may help refine clinical management strategies for severe ARI.

    Methods: We conducted an observational study of ARI among otherwise healthy, 0-65y individuals at five US military hospitals. Nasopharyngeal swabs were collected at enrollment and tested by a multiplex respiratory pathogen panel (Diatherix Laboratories, Inc.; Huntsville, AL) targeting 9 viruses (rhinovirus, influenza, adenovirus, coronavirus, coxsackievirus/echovirus, RSV, parainfluenza, human metapneumovirus and bocavirus) and 10 bacteria. Demographics and risk factors were collected at baseline. Symptom severity was recorded over 10 days via patient diary. 

    Results: Specimens from 898 enrollees (637 adults and 261 children) were evaluated on multiplex PCR respiratory panel. Of these, 315 (35.1%) were negative for a viral pathogens and these subjects represented older, Caucasian population with low likelihood of having young children in the household. In general, both children and adults with unidentified viral etiology had milder symptoms, including less hospitalization among children (p=0.04). However, more moderate/severe diarrhea (13.2% vs. 5.9%, p<0.01) and nausea (28.5% vs. 21.5%, p=0.04) was reported among adults with unidentified viral etiology. In addition, they were more likely to report use of antibiotics (35.6% vs. 24.7%, p<0.01) and to have abnormal chest X-rays if taken (34.4% vs. 13.6%, p=0.02) than those with known viral etiology. Adults with unidentified viral etiology had higher detection of bacterial respiratory pathogens (72.4% vs. 61.1%, overall; p<0.01), including Moraxella catarrhalis, Mycoplasma pneumoniae, and Streptococcus pyogenes.

    Conclusion: ARI cases with unidentified viral etiology tended to be older and to have milder symptoms. The possible contribution of bacterial respiratory pathogens to ARI needs further evaluation and may affect management strategies for these patients.

    Wei-Ju Chen, PhD1, John Arnold, MD2, Mary Fairchok, MD1,3, Christina Schofield, MD FACP, FIDSA4, Kristina J. St. Clair, DO, MTM&H5,6, Patrick Danaher, MD, FIDSA7, Michael Rajnik, MD8, Erin Mcdonough, BS9, Deepika Mor, MS1, Michelande Ridore, MS10, Timothy Burgess, MD, MPH8, Leslie Malone, MS, MB(ASCP)CM11, Elena Grigorenko, PhD12, Don Stalons, Ph.D., D(ABMM), MPH12, Eugene Millar, PhD13 and Henry M. Jackson Foundation for the Advancement of Military Medicine, (1)Infectious Disease Clinical Research Program, Uniformed Services University, Bethesda, MD, (2)Naval Medical Center San Diego, San Diego, CA, (3)Pediatrics, Madigan Army Medical Center, Tacoma, WA, (4)Madigan Army Medical Center, Tacoma, WA, (5)Uniformed Services University of the Health Sciences, Bethesda, MD, (6)Naval Medical Center Portsmouth, Portsmouth, VA, (7)San Antonio Military Health System, Fort Sam Houston, TX, (8)Walter Reed National Military Medical Center, Bethesda, MD, (9)Naval Health Research Center, San Diego, CA, (10)Infectious Disease Clinical Research Program, Uniformed Services University of the Health Sciences, Rockville, MD, (11)Diatherix Laboratories, Inc., Huntsville, AL, (12)Diatherix Laboratories, Inc, Huntsville, AL, (13)Infectious Disease Clinical Research Program, Rockville, MD


    W. J. Chen, None

    J. Arnold, None

    M. Fairchok, None

    C. Schofield, None

    K. J. St. Clair, None

    P. Danaher, None

    M. Rajnik, None

    E. Mcdonough, None

    D. Mor, None

    M. Ridore, None

    T. Burgess, None

    L. Malone, Diatherix Lab: Investigator , Salary

    E. Grigorenko, Diatherix lab: Investigator , Salary

    D. Stalons, Diatherix: Employee , Salary

    E. Millar, None

    Findings in the abstracts are embargoed until 12:01 a.m. PDT, Wednesday Oct. 7th with the exception of research findings presented at the IDWeek press conferences.