INTRODUCTION
Acute respiratory infections (ARI; e.g. pneumonia, tracheitis) are the most common cause of hospitalization, readmission, and death for children with tracheostomies.1-3 Clinicians frequently obtain bacterial respiratory cultures in this high risk population, both during times of respiratory illness and when well (i.e., “surveillance”). Depending on the clinical situation, cultures may be used as screening tests, diagnostic tests, or therapy-directing tests. During illness, culture results inform both diagnosis of infection and antibiotic prescribing. Surveillance cultures, when performed, are used to inform the diagnosis and treatment of bacterial colonization of the respiratory tract that may contribute to chronic airway inflammation, increased propensity to recurrent infection, and long-term respiratory decline.4 However no clinical guideline exists to guide clinician ordering or interpretation of respiratory cultures.5,6
Although easy to order and obtain in children with tracheostomies, the interpretation of respiratory cultures is highly complex due to many confounding factors, which have largely been understudied.7 A major contributor to the difficulty in interpreting culture results in this population is a lack of a robust epidemiologic understanding of organisms expected to be isolated during true ARI, let along during states of wellness. The respiratory tract, unlike other body compartments from which cultures are obtained (e.g., urine, blood), is not a sterile site and harbors oropharyngeal flora in children with and without tracheostomies.8 Respiratory cultures are often positive when children are not acutely ill among children with and without tracheostomies, although the organisms expected during wellness and their significance is unclear. Furthermore, evolving respiratory microbiome research among children with tracheostomies suggests dynamic bacterial changes during ARI which may change culture interpretation based on illness day.9,10 The interpretation of respiratory cultures is further obscured by concerns for sampling bias, repeated respiratory culture testing, potential bacterial colonization of the trachea and tracheostomy tube, and laboratory variation.
There is a limited understanding of how respiratory culture growth differs between children with tracheostomies when ill (with ARI) and when healthy (without ARI), limiting the understanding of this test’s utility in screening for, diagnosing, and/or treating ARI.11 Furthermore, although frequently ordered, diagnostic yield and test characteristics of respiratory cultures are unknown. This leads to challenges in diagnosing ARI, deciding when antibiotic therapy is indicated and, when treating, which bacteria to target.
In this study of children with tracheostomies, we sought to determine the epidemiology of respiratory culture organism isolation and to associate organism isolation with clinician-diagnosed ARI. We additionally assessed the performance of respiratory culture in the diagnosis of ARI. We hypothesized that children would have higher likelihood of organism isolation during ARI, and that respiratory cultures have limited predictive utility in screening for and diagnosing ARI.