Bronchopulmonary dysplasia (BPD) is a major neonatal respiratory condition that mainly affects preterm infants and can lead to long-term respiratory complications and increased healthcare costs (Van de Loo et al., 2024). The burden of BPD extends beyond the individual, placing substantial economic strain on healthcare systems due to prolonged hospitalization, increased medical interventions, and the need for ongoing respiratory support (Bhandari and Alexiou, 2023). Current management strategies for BPD primarily rely on supportive care, such as mechanical ventilation, oxygen therapy, and surfactant administration (Van de Loo et al., 2024). However, these approaches are limited in their inability to target the underlying pathophysiological mechanisms and the variability in treatment responses among affected infants. Therefore, it is essential to understand the mechanisms that contribute to the development of BPD. The immune processes that drive disease progression remain poorly understood (Fang et al., 2024). In this context, the significance of airway microbiota has been proposed (Natalini et al., 2023). Once thought to be a sterile environment, the lungs are now recognized as being routinely exposed to a diverse array of microorganisms (Natalini et al., 2023).

In recent times, significant progress and the adoption of culture-independent molecular sequencing techniques, especially high-throughput innovations like next-generation sequencing, have markedly improved the capacity to dynamically analyze microbial communities located in diverse areas of the human body (El Saie et al., 2022). The microbiota within the pulmonary system is essential for sustaining the functional equilibrium of the lungs (Liu et al., 2022). Studies have revealed a strong link between the pulmonary microbiota and the onset and progression of various respiratory disorders (Liu et al., 2022). Evidence from human studies suggests that microbial exposures begin early in life, typically within days to weeks after birth, and play a crucial role in the maturation of the immune system (Mishra et al., 2021). However, the specific mechanisms by which alterations in the airway microbiome contribute to ongoing immune activation and the resultant lung injury are still not fully understood. The mechanisms that facilitate the interaction between the microbiome and immune responses in the airways have not been fully elucidated (Kayongo et al., 2022). The precise pathways through which modifications in the microbiome influence the onset of BPD are not yet thoroughly elucidated. Furthermore, the impact of microbiota on the underdeveloped lung and the associated risk for BPD remains controversial (Dong et al., 2022).

Previous studies has highlighted the potential role of the microbiome in the development and progression of BPD. However, the specific microbial characteristics and their evolution in infants with BPD, compared with those without, remain insufficiently explored (Staude et al., 2023). This study aimed to fill this knowledge by investigating the microbiome features and their dynamics in infants diagnosed with BPD, contributing to a deeper understanding of the disease and potential avenues for targeted interventions. A comparative cohort design was employed to examine the microbiome characteristics and clinical features of infants diagnosed with BPD in contrast to a control group of infants without BPD. The primary objective of this pilot research was to characterize the longitudinal development of the airway microbiome (at days 1, 7, and 14 after intubation) in preterm infants with and without BPD. By integrating clinical data with microbiome analysis, this study aimed to identify specific microbial taxa that may serve as biomarkers for BPD, ultimately supporting improved diagnostic and therapeutic strategies for affected infants.

Growing evidence substantiates the concept of an active interplay between the airway microbiota and pulmonary health (Kayongo et al., 2022; Natalini et al., 2023). The results of this investigation revealed the presence of various bacterial taxa within the respiratory secretions of intubated premature infants, with these microorganisms being identifiable from the moment of birth. The dominance of Firmicutes and Proteobacteria in the BPD group at intubation, compared with the predominance of Firmicutes and Tenericutes in the non-BPD group, highlights the potential role of specific microbial taxa in influencing the risk of developing BPD, consistent with the previous studies (Lohmann et al., 2014; Lal et al., 2018). This study adds value through its longitudinal design with specific sampling time points in the preterm infants, capturing dynamic changes of airway microbiota early in life. The key observation was the notable differences over time in the respiratory microbiomes of infants who later developed BPD versus those who did not, as measured by α-diversity and β-diversity. Infants with BPD exhibited decreased Shannon index values and increased Simpson index values, suggesting reduced species richness with a relatively uniform distribution, potentially dominated by a limited number of taxa. Consistent with previous studies, the reduced bacterial diversity observed in the BPD cohort of the study, suggests a potential disruption in microbial homeostasis that may contribute to the pathophysiology of BPD (Lohmann et al., 2014). This is consistent with findings that suggest a varied microbiome plays a crucial role in the development of the immune system and the maintenance of respiratory health in newborns (Pirr et al., 2025).

Moreover, the evolution of the microbiome over the first two weeks of life provides critical insights into the dynamic nature of microbial colonization in preterm infants, suggesting that the microbial landscape is shaped not only by initial colonization but also by subsequent environmental and physiological factors. It has been reported that pulmonary microbial diversity may be affected by invasive mechanical ventilation (Liu et al., 2022). Specifically, high oxygen (O₂) inhalation-induced oxygen toxicity may reduce the diversity of the pulmonary microbiota, potentially leading to poor prognosis. Moreover, fluctuations in localized O₂ levels may decrease the variability of the pulmonary microbiome by affecting the immune micro-environment within the lungs (Liu et al., 2022). In mice subjected to hyperoxic conditions, there was a marked alteration in the relative abundance of pulmonary bacteria when compared to those maintained under normoxic conditions, accompanied by a significant reduction in bacterial diversity (Ashley et al., 2020). It can be concluded that elevated oxygen levels during invasive mechanical ventilation may influence the diversity of microbiota by affecting the proliferation rates of intricate microorganisms within the pulmonary microbiota. This finding necessitates additional investigations both in vitro and in clinical settings (Ashley et al., 2020). Notably, it is well-documented that antibiotic exposure leads to gut microbiome dysbiosis in early life and prolonged exposure to broad-spectrum antibiotics has been associated with an increased incidence of BPD (Shi et al., 2024). Narrow-spectrum antibiotics including cephalosporin and penicillin were used as empirical antibiotic treatment to prevent infection for the enrolled preterm infants in this study. The results indicated that the infants with BPD received prolonged antibiotic treatment compared to controls, which may alter the lung microbiome and immune responses, potentially increasing the risk of BPD development, but the precise mechanism was not clear. The MetaCyc pathway analysis of the airway microbiome in this study showed an significant elevation in the pentose phosphate pathway in the BPD infants. The over-activation of the pentose phosphate pathway has been reported to promote BPD development (Gong et al., 2021).

In preterm infants of the study, both groups exhibited dominance of Staphylococcus and Ureaplasma genera in the early airway microbiome, consistent with previous studies (Pammi et al., 2019). Preterm delivery is a primary contributor to neonatal morbidity and mortality worldwide, with Ureaplasma species being the most commonly identified microorganisms in amniotic fluid and placental samples in such cases (Pammi et al., 2019). The presence of Ureaplasma colonization has been associated with various adverse outcomes, including infertility, stillbirth, histological chorioamnionitis, and several neonatal complications such as congenital pneumonia, BPD, meningitis, and perinatal mortality (Sprong et al., 2020). Ureaplasma was abundant at birth but reduced over time in both groups. Prior research has indicated that Ureaplasma contributes distinctly to the development of BPD. Nevertheless, recent meta-analyses have failed to deliver uniform evidence to validate this association (Van Mechelen et al., 2023). The existing definitions and classifications of BPD, which mainly focus on the need for respiratory support rather than underlying pathophysiological processes and phenotypic variations, present certain limitations (El-Saie et al., 2023). As a result, the exact mechanisms by which Ureaplasma infection induces changes in lung development, as well as the pathways leading to different BPD phenotypes, require further research to enhance our understanding.

The evolutionary trajectory of the microbiome in infants with BPD showed significant divergence from that of their non-BPD counterparts. This study showed that a decreased relative abundance of the phyla Bacteroidetes and Proteobacteria over time, along with an increased relative abundance of Firmicutes, may be associated with BPD progression, consistent with the research by Pablo Lohmann et al (Lohmann et al., 2014). This shift in microbial composition may reflect altered metabolic capacity and could potentially influence the inflammatory processes associated with BPD (Tanabe et al., 2025). In contrast to this study, Charitharth Vivek Lal and colleagues discovered that the airway microbiome in infants with BPD exhibited a higher prevalence of Proteobacteria, alongside a reduced presence of Firmicutes (Lal et al., 2016). Differences in the clinical characteristics of the patients, variations in the methodologies used, or disparities in the environmental ecology of the research sites may explain this discrepancy. Furthermore, The results indicated an increased proportion of Streptococcus (facultative anaerobe) and Acinetobacter (aerobe) genera at day 14 of life, which may suggest the presence of ventilator-associated pneumonia or longer oxygen supplementation (Lu et al., 2014). Streptococcus might promote BPD development via TLR signaling and MyD88-dependent signaling pathways (Park et al., 2019; Diaz-Dinamarca et al., 2023). Furthermore, a decrease in Prevotella was observed in BPD infants. The genera Prevotella can produce short-chain fatty acids, which have been demonstrated to be involved in the development and progression of BPD (Li et al., 2020; Gao et al., 2024). These findings raise questions about the potential pathogenic roles these organisms may play in BPD, highlighting the need for further investigation into their contributions to disease progression. In contrast, the dominance of specific genera in infants who did not develop BPD may suggest a protective role in preventing the condition. Additionally, we noted a significant decrease in Lactobacillaceae at day 7 post-birth. Recent data has shown that supplementation with Lactobacillus strains can improve lung architecture and functionality, diminish the influx of neutrophils, and lower various pro-inflammatory markers of BPD in mice models, likely mediated by the matrix metalloproteinase/proline-glycine-proline pathway (Nicola et al., 2024).

The strengths of this study lie in its thorough approach to characterizing the microbiome of infants with and without BPD during key early developmental stages, thereby providing the potential of leveraging microbiome biomarkers for early BPD risk prediction and developing targeted probiotic interventions. By utilizing a well-designed cohort that includes both the BPD group and the non-BPD group, the study effectively accounts for potential confounding factors such as GA, BW, and sex distribution, thereby improving the reliability of the findings. Advanced microbiome analysis methods, such as Shannon and Simpson diversity indices and LEfSe, offer a detailed understanding of microbial community dynamics and their potential role in BPD development. Additionally, the longitudinal analysis of microbial diversity from birth to day 14 provides valuable insights into how microbial populations evolve over time in relation to BPD. This comprehensive approach not only enhances the robustness of the results but also adds to the growing body of evidence connecting early microbial exposure with respiratory outcomes in preterm infants.

Collectively, these findings highlight the crucial role of the microbiome in the pathophysiology of BPD and suggest that further exploration of microbial interventions could offer the potential as a novel targeted therapeutic strategy in the BPD treatment. Future research should focus on investigating the relationship between the airway metabolome and microbiome in the context of respiratory diseases.