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.