Association of toll-like receptors with the airway-intestinal microbiota and pneumonia development in preterm infants - A case control study.

Background: The prevention and treatment of pneumonia and lung injury in preterm infants are major challenges for pediatricians worldwide. Few studies have analyzed the composition of bacterial colonies in the airway and intestine and their relationship with toll-like receptors (TLRs) as it relates to pneumonia in preterm infants.

Methods: This study included 70 infants born at 32-35 weeks gestation. Oral-tracheal aspirates at the time of birth, first-pass meconium, and serum specimens were collected. Bacterial deoxyribonucleic acid (DNA) was extracted from the Oral-tracheal aspirates and meconium, and 16S ribosomal ribonucleic acid (rRNA) genes were amplified and sequenced. The levels of TLR2 and TLR4 were analyzed using an enzyme-linked immunosorbent assay. Preterm infants were classified into non-pneumonia (A) and pneumonia (B) groups according to their clinical manifestations.

Results: Significant differences in the alpha and beta diversities were observed between the two groups. Infants with pneumonia had less bacterial diversity in the airways and intestinal flora at birth than those without pneumonia. The three most predominant phyla in the airways at birth were Proteobacteria, Firmicutes, and Actinobacteria. The levels of TLR2 and TLR4 in oral-tracheal aspirates were higher in infants with pneumonia than in those without pneumonia, although serum TLR2 and TLR4 levels did not differ between the groups. Streptococcus in the oral tracheal aspirate was negatively correlated with TLR2 and TLR4 levels, and Ureaplasma in the oral-tracheal aspirate was negatively correlated with TLR4 levels in the airway.

Conclusion: Reduced perinatal microbiota diversity is associated with the levels of TLR2 and TLR4, and may also have a significant impact on the development of pneumonia.