Bacterial Colonization within the First Six Weeks of Life and Pulmonary Outcome in Preterm Infants <1000 g

Abstract

Bronchopulmonary dysplasia (BPD) is a multifactorial disease mainly provoked by pre- and postnatal infections, mechanical ventilation, and oxygen toxicity. In severely affected premature infants requiring mechanical ventilation, association of bacterial colonization of the lung and BPD was recently disclosed. To analyze the impact of bacterial colonization of the upper airway and gastrointestinal tract on moderate/severe BPD, we retrospectively analyzed nasopharyngeal and anal swabs taken weekly during the first 6 weeks of life at a single center in n = 102 preterm infants <1000 g. Colonization mostly occurred between weeks 2 and 6 and displayed a high diversity requiring categorization. Analyses of deviance considering all relevant confounders revealed statistical significance solely for upper airway colonization with bacteria with pathogenic potential and moderate/severe BPD (p = 0.0043) while no link could be established to the Gram response or the gastrointestinal tract. Our data highlight that specific colonization of the upper airway poses a risk to the immature lung. These data are not surprising taking into account the tremendous impact of microbial axes on health and disease across ages. We suggest that studies on upper airway colonization using predefined categories represent a feasible approach to investigate the impact on the pulmonary outcome in ventilated and non-ventilated preterm infants.

Keywords: bacterial colonization; bronchopulmonary dysplasia; gram-negative bacteria; gut; lung; pathogenic; preterm infant; upper airway.

Figure 1

Frequency of overall bacterial colonization of the upper respiratory tract and the gut in the study cohort. Depicted are the frequencies of total bacterial colonization of the upper respiratory tract (A) and the gut (B) investigated by nasopharyngeal and anal swabs within the first six weeks of life. The additional category comprises the cases were no positive result was obtained within the observational period (>6). Green sections of bars represent infants with no/mild BPD, and red sections preterms with moderate/severe BPD.

Figure 2

Frequency of colonization of the upper respiratory tract and the gut by bacterial categories within the study cohort. Depicted are the frequencies of bacterial colonization of the upper respiratory tract (A,B) and the gut (C,D) investigated by nasopharyngeal and anal swabs within the first six weeks of life. The additional category comprises the cases were no positive result was obtained within the observational period (>6). Bacterial strains were separated for their pathogenic potential (A,C) and Gram staining reaction (B,D). Graphics are displayed for BPD disease severity as in Figure 1.