title: The lack of specificity of tracheal aspirates in the diagnosis of pulmonary infection in intubated children.
abstract: OBJECTIVE
  Ventilator-associated pneumonia is the first or second most commonly diagnosed nosocomial infection in the PICU. Centers for Disease Control diagnostic criteria include clinical signs or symptoms in conjunction with a "positive" tracheal aspirate, defined as more than 10 colony-forming units/mL of bacteria on quantitative culture and/or more than 25 polymorphonuclear neutrophils per low-power field on Gram stain. We hypothesized that tracheal aspirate cultures and Gram stains would not correlate with clinical signs and symptoms and would therefore not distinguish between colonization and infection.
  
  
  METHODS
  Prospective observational study.
  
  
  METHODS
  PICU in an academic tertiary care center.
  
  
  METHODS
  Children intubated more than 48 hours.
  
  
  METHODS
  Sequential tracheal aspirate quantitative cultures and Gram stains in conjunction with daily collection of concordant clinical signs and symptoms.
  
  
  RESULTS
  Time since intubation correlated strongly (p < 0.001) with the proportion of positive (> 10 colony-forming units/mL) tracheal aspirate quantitative cultures, but Centers for Disease Control-defined clinical signs or symptoms of ventilator-associated pneumonia, either singly or in combination, did not. Use of in-line suction catheters versus new, sterile catheters to obtain tracheal aspirates was associated with significantly greater proportion of positive tracheal aspirate bacterial cultures (p < 0.001). Most subjects had more than 25 polymorphonuclear neutrophils per low-power field on Gram stain; polymorphonuclear neutrophils on Gram stain correlated with positive bacterial culture (p = 0.04). Seventy-seven percent of the bacterial isolates detected in positive quantitative cultures were "pathogens." Antibiotic use at the time tracheal aspirates were obtained was associated with a lower frequency of positive quantitative cultures only with antibiotic regimens that included cefepime.
  
  
  CONCLUSIONS
  Positive bacterial cultures of tracheal aspirates increase rapidly after intubation and usually include bacteria considered to be pathogens. Tracheal aspirate cultures and Gram stains do not appear to distinguish between infection and colonization. Antibiotic regimens that include cefepime decrease the frequency of positive cultures, but the significance of this is unclear.
authors.affiliation: 1Division of Pediatric Critical Care, Department of Pediatrics, University of Virginia Health Sciences System, Charlottesville, VA. 2Department of Public Health Sciences, University of Virginia Health Sciences System, Charlottesville, VA. 3Division of Pediatric Infectious Disease, Department of Pediatrics, University of Virginia Health Sciences System, Charlottesville, VA.
authors.forename: Douglas F
authors.initials: DF
authors.lastname: Willson
authors.forename: Mark
authors.initials: M
authors.lastname: Conaway
authors.forename: Robin
authors.initials: R
authors.lastname: Kelly
authors.forename: J Owen
authors.initials: JO
authors.lastname: Hendley
mesh_terms: D000900:Anti-Bacterial Agents / Q000627:therapeutic use; D057785:Catheters / Q000382:microbiology; D000077723:Cefepime; D002511:Cephalosporins / Q000627:therapeutic use; D002675:Child, Preschool; D015169:Colony Count, Microbial; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D015278:Intensive Care Units, Pediatric; D007442:Intubation, Intratracheal / Q000009:adverse effects*; D008297:Male; D009504:Neutrophils; D018410:Pneumonia, Bacterial / Q000175:diagnosis* / Q000188:drug therapy / Q000382:microbiology; D053717:Pneumonia, Ventilator-Associated / Q000175:diagnosis* / Q000188:drug therapy / Q000382:microbiology; D011446:Prospective Studies; D012121:Respiration, Artificial / Q000009:adverse effects*; D013997:Time Factors; D014132:Trachea / Q000276:immunology / Q000382:microbiology*
chemical_list: D000900:Anti-Bacterial Agents; D002511:Cephalosporins; D000077723:Cefepime