Abbreviations: OR: odds ratio; CI: confidence interval.a Calculated using a generalized estimating equation to control for patient-level covariates [including: number of complex chronic conditions, ventilator use, race, ethnicity, insurance type], culture-level covariates [including: age at culture acquisition, time with tracheostomy at culture acquisition, department obtained], and to account for within-patient clustering.b Examining the 115 cultures of the 20 children who had chronic P. aeruginosa isolation, defined as P. aeruginosa isolation on ≥50% of respiratory cultures obtained in a 12 month period in the same child, using an adaptation of previously-described criteria.15c Calculated using a generalized estimating equation to control for patient-level covariates [including: number of complex chronic conditions, ventilator use, race], culture-level covariates [including: age at culture acquisition, time with tracheostomy at culture acquisition], and to account for within-patient clustering. For Staphylococcus analysis, covariates included only number of complex chronic conditions and ventilator use.