Microbial colonization of the lower airways after insertion of a cuffed endotracheal tube in pediatric patient

Background. Ventilator-associated pneumonia (VAP) still remains a common device-associated hospital acquired infection in pediatric and adult intensive care units. The aim of our study was to determine ways of microbial transmission to the lower airways in intubated patients admitted to a single tertiary-care pediatric intensive care unit. Methods. This was a prospective observational study. A total of 284 sample sets (oropharyngeal swabs, swabs from the lumen of the proximal tip of an endotracheal tube, and bronchoalveolar lavage samples) were collected from 62 consecutive pediatric patients intubated for > 24 hours. Pulsed-field gel electrophoresis was performed on all isolated pathogens, which were later identified by MALDI biotyper (MALDI-TOF mass spectrometry). Results. Overall colonization rates were high and did not differ significantly at different time points in the oropharynx (75%-100%) and the lower airways (50%-76.5%). The endotracheal tube was colonized at lower rates: on day 1-3 (28.8%), on day 4-6 (52.7%), on day 7-9 (61.8%) and on day 10-12 (52.9%) (P < 0.001). A total of 191 matched sample sets from the lower airways and at least one site above were collected from 46 (74.2%) patients. In the oropharynx-lower airways group, Candida spp. (76.9%) and upper airway bacteria (63.2%); in the endotracheal tubelower airway group, S. aureus (15.7%) and upper airway bacteria (21.1%); in the oropharynx-endotracheal tube-lower airway group, Enterobacteriaceae (70.8%) prevailed (P < 0.001). The mean survival (entrance) time to lower airways for the Acinetobacter / Pseudomonas / Stenotrophomonas group was 8.28 +/- 0.81 days; for the Enterobacteriaceae group, 5.63 +/- 0.41; and for Candida spp. group, 3.00 +/- 0.82 days (P < 0.005). Conclusions. Oropharyngeal contamination of the lower airways is the most important route of colonization. Different pathogens enter the lower airways at different time intervals from the insertion of an endotracheal tube.