Diagnostic Utility of Tracheal Aspirate Cultures in the Neonatal Intensive Care Unit

Abstract

Research Question: Are neonatal intensive care unit (NICU) clinicians accurately discriminating between infection and colonization of the upper respiratory tract based on results from endotracheal aspirate cultures (ETAs) of neonates in their evaluation of sepsis? Further, what are the qualitative results of these cultures and how are they related to the antimicrobial treatment method? We hypothesized that the results of the ETAs, regardless of colonization or infection, influence antimicrobial treatment of intubated neonates. The goal of this study is to determine the utility of ETA cultures in routine septic evaluations in the NICU.

Background and Significance: Ventilatory?associated pneumonia (VAP) is a serious concern that entails high resource utilization in the NICU. Qualitative tracheal aspirate cultures are commonly utilized in VAP¿s diagnostic work?up. These cultures lack specificity for infection or pathology and have not been shown to differentiate between colonization and infection. The complex microbial community residing in the lungs has been proven to be important for the maintenance of homeostasis. This shift in view of the lungs as a site of colonization calls for new guidelines for interpreting positive ETAs, a routine part of a sepsis work?up in the NICU, and resultant treatment. This study will aid in outlining the microbial characteristics and current practices in treatment of positive ETAs.

Materials and Methods: Using data obtained from tracheal aspirates from neonates, we classified patients based on the following: age, sex, EGA at birth, birth weight, EGA at time of culture, tracheal aspirate source, and simultaneous cultures. Cultures were detailed by organisms grown. Treatment was categorized based on the presence antibiotics used empirically at the time of culture, antibiotics used to treat any positive culture for greater than two days, and documented diagnosis. Surveying attending physicians at Cook Children¿s Medical Center, we have elucidated patterns of infection identification and antibiotic prescribing practices for intubated neonates. This was done using a questionnaire that automatically given to physicians of neonates with a positive ETA. The survey inquired about the physician¿s decision to obtain a tracheal culture, whether the results of the culture influenced treatment, their suspected diagnosis at the time of the culture and subsequent diagnosis 48 hours after the culture. The physicians were also asked to describe the factors used to distinguish colonization versus infection. Ultimately, the survey provides insight into determining if physicians¿ decision to treat positive cultures was in accordance with published guidelines and definitions of VAP and tracheitis.

Results: We hypothesized that the tracheal aspirate cultures would be characterized by a variety of colonizing organisms and correlated antimicrobial treatment because of the ETA, regardless of diagnosis. More patients with positive ETAs were prescribed antibiotics due to this result than there were cases of true infection, and even those with suspected tracheal colonization.

Conclusion: Physicians also overestimated the incidence of true infection, leading to additional unnecessary antibiotic use. It is imperative that the diagnostic utility of tracheal aspirate cultures be refined as antibiotic resistance continues to become more prevalent and the impact of unnecessary antibiotic use is not neutral for these patients and may have lasting effects.