(836) Lower Respiratory Cultures in Previously Health Infants Intubated for LRTI: A BACON Substudy

Introduction: Bronchiolitis and lower respiratory tract infections (LRTIs) are common causes of respiratory failure/intubation in infants. Bacteria are considered for pneumonia (pna) though may also be associated with severe bronchiolitis. While bronchiolitis care is supportive, antibiotics are often used in pna. We proposed that in previously healthy infants intubated for LRTI, a positive respiratory culture is more common in pna and associated with worse outcomes.

Methods: This is a sub-analysis of a prospective study of children < 2 years intubated for LRTI between 12/2020 and 11/2021. All sites obtained lower respiratory cultures after intubation. A respiratory culture was positive if it had any growth of pathogenic bacteria. Data reported as n (%) or median (IQR) and analyzed using chi-square or Wilcoxon rank sum.

Results: Of 592 enrolled, 263 previously healthy children were analyzed (median age 3 months; 33% male). Admission diagnoses were: pna (16%), bronchiolitis (65%), bronchiolitis & pna (9%), and neither (10%). 60% had a positive respiratory culture (PosCx). PosCx were more common in bronchiolitis (70%) than pna (40%), younger age (2 vs 5.2 months; p< 0.001) and more likely to present with retractions (62% vs 49%) or coarse breath sounds (30% vs 15%), a positive viral test (88% vs 68%) and have RSV (69% vs 49%). Those with negative cultures more commonly had fever or wheezing (42% vs 28%; p=0.014). Mortality was rare (2.7%). Ventilation duration and ICU stay didn’t differ by culture results. H. influenzae was most common in bronchiolitis (27%) and pna (22%). S. pneumonia and M. catarrhalis were common only in bronchiolitis (17% and 20% respectively vs 4% and 7% in pna). Early antibiotics were common in bronchiolitis and pna (86% and 100%, respectively) and were continued >4 days for 69% with bronchiolitis and 79% with pna.

Conclusions: A positive respiratory culture was less common in pna than bronchiolitis for many possible reasons, including the following: pediatric pna is frequently viral, our ability to distinguish bronchiolitis from pna is poor, admit diagnoses may not reflect the true diagnosis, and positive respiratory cultures may not mean a true infection. There may be diagnostic overlap, and future studies should focus on better testing and definitions to improve antibiotic decisions.