413 - Tracheal Aspirate Cultures Guide Antimicrobial Therapy in Mechanically Ventilated Infants in a Level IV NICU

Mechanically ventilated infants are at risk of acquired respiratory infections, although diagnostic tools for identification of ventilator associated tracheitis (VAT) or pneumonia (VAP) are limited. Tracheal aspirate (TA) cultures are often analyzed in the neonatal intensive care unit (NICU) to aid in diagnosis despite inherent limitations in obtaining adequate samples and differentiating bacterial colonization from true infection. 

Objective:

We aimed to understand the use and interpretation of TA cultures in a Level IV NICU.

Design/Methods:

All mechanically ventilated infants in our Level IV NICU who had a TA culture obtained during calendar year 2019 were identified. Clinical variables and details of each TA sample were obtained from the electronic medical record (EPIC).

Results:

Total of 255 TA cultures in 70 infants were analyzed; median gestational age at birth was 29 weeks and infants were a mean of 107 days at time of TA collection. Infants in this cohort had 1.2 tracheal aspirates sent per 10 ventilator days, and on average had 3.6 ETTs placed, with the most recent intubation a mean of 28 days prior to obtaining TA culture during hospitalization. Most common indication for TA culture was sepsis evaluation due to clinical instability (38%), increased/thickened secretions (32%), fever (20%), and increased severe hypoxic events or new severe hypoxic event (17%). Most common organisms identified were mixed upper respiratory flora (15%), unspecified lactose fermenter (14%), and methicillin-susceptible Staphylococcus aureus (MSSA) (10%); 67% of these were considered pathogenic bacterial growth. Most common indications for initiating antibiotic treatment were bacterial growth on culture (19%), clinical concern for VAT (12%) and gram stain with moderate to heavy polymorphonuclear cells and/or moderate to heavy bacterial growth (12%). Typical length of treatment for infants with clinician diagnosed VAT was 6 days, and for VAP was 8.5 days; altogether infants received an average of 2.1 days of antimicrobials per TA culture.

Conclusion(s): High risk mechanically ventilated infants in the NICU will frequently be evaluated for an acquired respiratory infection with a TA culture and, oftentimes, more than once during their hospitalization. Indications for sending a TA culture are variable. These tests, while appropriate in the right clinical setting, may be associated with increased antibiotic exposure. Standardization of use and interpretation of a TA culture may improve clinical care and antibiotic stewardship efforts in this population.