D105-11 Pseudomonas Aeruginosa Phenotypes Among Children Hospitalized With Tracheostomy-associated Respiratory Infections

Rationale Children hospitalized with tracheostomy-associated respiratory infections (TARI) (e.g., pneumonia, tracheitis) frequently receive antibiotic treatment for Pseudomonas aeruginosa (Pa). Chronic Pa has been associated with worse clinical outcomes for children with tracheostomy, however the mechanisms for this observation remain largely unknown. We sought to characterize Pa bacterial phenotypes among children with tracheostomy to identify Pa’s role in clinical TARI presentation. Methods We conducted a nested, cross-sectional study within a prospective, multicenter observational cohort study of airway Pa isolates from patients 0-17 years with pre-existing tracheostomy hospitalized with TARI. Genomic and plasmid DNA were sequenced according to the Oxford Nanopore NO-MISS protocol and subjected to 1) O-antigen serotyping, 2) exotoxin typing (exoU/S) and 3) multi-locus strain typing (MLST). Pa isolates were also assessed for serum-associated tolerance (SAT) to antibiotics defined as 100-fold increase in colony forming units when grown in human serum vs. Luria-Bertani medium when exposed to ciprofloxacin, gentamicin, or tobramycin. Patient and clinical data from each TARI encounter were abstracted from the electronic health record. Relationships between Pa phenotypes and clinical data were assessed using hierarchical clustering and visualized with the R package ggtree. Groups were compared using Wilcoxon rank sum and Fisher’s exact tests. Results A total of 28 Pa isolates obtained from 18 unique participants were studied. The median age of the cohort was 3 years (interquartile range (IQR): 0.9,4.5), and participants frequently had comorbid neuromuscular disease (78%) and received home mechanical ventilation (56%). The most frequent serotypes were O6 (39%) and O5 (25%); 6 isolates harbored the more virulent exoU exotoxin (Figure). Isolates taken from the same participant clustered indicating clonal colonization. Patients with exoU+Pa had longer duration of increased ventilatory support (5 days [IQR: 4.3-10.2]) vs. 0 days [IQR: 0-1.8], p=.003) and longer duration of increased oxygen support (5.5 days [IQR: 1.3-6] vs. 1 day [IQR: 0-2.8]), (p=.06). SAT was detected in 36% of isolates and 50% of patients. For encounters with SAT-positive isolates, patients more frequently presented with fever (50% vs. 39%), hypoxemia (90% vs. 61%), tachypnea (30% vs 17%), and increased tracheostomy secretions (60% vs. 39%) compared to SAT-negative encounters. Although not statistically significant, some differences appear clinically relevant. Conclusions The Pa exoU exotoxin was associated with more severe illness and may serve as a biomarker for short-term outcomes in TARI. Future studies investigating the role of exotoxin and other Pa phenotypes in long-term respiratory infection outcomes are warranted.