title: A pilot study of the noninvasive assessment of the lung microbiota as a potential tool for the early diagnosis of ventilator-associated pneumonia.
abstract: BACKGROUND
  Ventilator-associated pneumonia (VAP) remains a common complication in critically ill surgical patients, and its diagnosis remains problematic. Exhaled breath contains aerosolized droplets that reflect the lung microbiota. We hypothesized that exhaled breath condensate fluid (EBCF) in hygroscopic condenser humidifier/heat and moisture exchanger (HCH/HME) filters would contain bacterial DNA that qualitatively and quantitatively correlate with pathogens isolated from quantitative BAL samples obtained for clinical suspicion of pneumonia.
  
  
  METHODS
  Forty-eight adult patients who were mechanically ventilated and undergoing quantitative BAL (n = 51) for suspected pneumonia in the surgical ICU were enrolled. Per protocol, patients fulfilling VAP clinical criteria undergo quantitative BAL bacterial culture. Immediately prior to BAL, time-matched HCH/HME filters were collected for study of EBCF by real-time polymerase chain reaction. Additionally, convenience samples of serially collected filters in patients with BAL-diagnosed VAP were analyzed.
  
  
  RESULTS
  Forty-nine of 51 time-matched EBCF/BAL fluid samples were fully concordant (concordance > 95% by κ statistic) relative to identified pathogens and strongly correlated with clinical cultures. Regression analysis of quantitative bacterial DNA in paired samples revealed a statistically significant positive correlation (r = 0.85). In a convenience sample, qualitative and quantitative polymerase chain reaction analysis of serial HCH/HME samples for bacterial DNA demonstrated an increase in load that preceded the suspicion of pneumonia.
  
  
  CONCLUSIONS
  Bacterial DNA within EBCF demonstrates a high correlation with BAL fluid and clinical cultures. Bacterial DNA within EBCF increases prior to the suspicion of pneumonia. Further study of this novel approach may allow development of a noninvasive tool for the early diagnosis of VAP.
authors.affiliation: Division of Trauma and Surgical Critical Care, Vanderbilt University, Nashville, TN. Electronic address: addison.may@vanderbilt.edu.
authors.forename: Addison K
authors.initials: AK
authors.lastname: May
authors.affiliation: Division of Trauma and Surgical Critical Care, Vanderbilt University, Nashville, TN.
authors.forename: Jacob S
authors.initials: JS
authors.lastname: Brady
authors.affiliation: Division of Neonatology, Vanderbilt University, Nashville, TN.
authors.forename: Joann
authors.initials: J
authors.lastname: Romano-Keeler
authors.affiliation: Department of Pathology, Microbiology, and Immunology, Vanderbilt University, Nashville, TN.
authors.forename: Wonder P
authors.initials: WP
authors.lastname: Drake
authors.affiliation: Division of Trauma and Surgical Critical Care, Vanderbilt University, Nashville, TN.
authors.forename: Patrick R
authors.initials: PR
authors.lastname: Norris
authors.affiliation: Division of Trauma and Surgical Critical Care, Vanderbilt University, Nashville, TN.
authors.forename: Judith M
authors.initials: JM
authors.lastname: Jenkins
authors.affiliation: Molecular Sensing Inc, Ohio University, Athens, OH.
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Isaacs
authors.affiliation: Department of Mathematics, Ohio University, Athens, OH.
authors.forename: Erik M
authors.initials: EM
authors.lastname: Boczko
mesh_terms: D018893:Bronchoalveolar Lavage / Q000295:instrumentation / Q000379:methods; D016638:Critical Illness; D004269:DNA, Bacterial / Q000235:genetics; D003955:Diagnostic Tests, Routine / Q000295:instrumentation / Q000379:methods*; D045853:Exhalation; D006801:Humans; D007362:Intensive Care Units; D008168:Lung / Q000382:microbiology*; D008828:Microbiological Techniques / Q000295:instrumentation / Q000379:methods*; D064307:Microbiota / Q000235:genetics*; D010865:Pilot Projects; D053717:Pneumonia, Ventilator-Associated / Q000175:diagnosis* / Q000382:microbiology*; D060888:Real-Time Polymerase Chain Reaction; D012044:Regression Analysis; D012680:Sensitivity and Specificity
chemical_list: D004269:DNA, Bacterial