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

Preterm Infants' Airway Microbiome: A Scoping Review of the Current Evidence

The aim of this scoping review was to investigate and synthesize existing evidence on the airway microbiome of preterm infants to outline the prognostic and therapeutic significance of these microbiomes within the preterm population and identify gaps in current knowledge, proposing avenues for future research. We performed a scoping review of the literature following the Arskey and O'Malley framework. In accordance with our inclusion criteria and the intended purpose of this scoping review, we identified a total of 21 articles. The investigation of the airway microbiome in preterm infants has revealed new insights into its unique characteristics, highlighting distinct dynamics when compared to term infants. Perinatal factors, such as the mode of delivery, chorioamnionitis, the respiratory support, and antibiotic treatment, could impact the composition of the airway microbiome. The 'gut-lung axis', examining the link between the lung and gut microbiome as well as modifications in respiratory microbiome across different sites and over time, has also been explored. Furthermore, correlations between the airway microbiome and adverse outcomes, such as bronchopulmonary dysplasia (BPD), have been established. Additional research in neonatal care is essential to understand the early colonization of infants' airways and explore methods for its optimization. The critical opportunity to shape long-term health through microbiome-mediated effects likely lies within the neonatal period.

Microbial signatures in amniotic fluid at preterm birth and association with bronchopulmonary dysplasia

BACKGROUND

Microbiome dysbiosis can have long-lasting effects on our health and induce the development of various diseases. Bronchopulmonary dysplasia (BPD) is a multifactorial disease with pre- and postnatal origins including intra-amniotic infection as main risk factor. Recently, postnatal pathologic lung microbiota colonization was associated with BPD. The objectives of this prospective observational cohort study were to describe differences in bacterial signatures in the amniotic fluid (AF) of intact pregnancies without clinical signs or risk of preterm delivery and AF samples obtained during preterm deliveries and their variations between different BPD disease severity stages.

METHODS

AF samples were collected under sterile conditions during fetal intervention from intact pregnancies (n = 17) or immediately before preterm delivery < 32 weeks (n = 126). Metabarcoding based approaches were used for the molecular assessment of bacterial 16S rRNA genes to describe bacterial community structure.

RESULTS

The absolute amount of 16S rRNA genes was significantly increased in AF of preterm deliveries and detailed profiling revealed a reduced alpha diversity and a significant change in beta diversity with a reduced relative abundance of 16S rRNA genes indicative for Lactobacillus and Acetobacter while Fusobacterium, Pseudomonas, Ureaplasma and Staphylococcus 16S rRNA gene prevailed. Although classification of BPD by disease severity revealed equivalent absolute 16S rRNA gene abundance and alpha and beta diversity in no, mild and moderate/severe BPD groups, for some 16S rRNA genes differences were observed in AF samples. Bacterial signatures of infants with moderate/severe BPD showed predominance of 16S rRNA genes belonging to the Escherichia-Shigella cluster while Ureaplasma and Enterococcus species were enriched in AF samples of infants with mild BPD.

CONCLUSIONS

Our study identified distinct and diverse intrauterine 16S rRNA gene patterns in preterm infants immediately before birth, differing from the 16S rRNA gene signature of intact pregnancies. The distinct 16S rRNA gene signatures at birth derive from bacteria with varying pathogenicity to the immature lung and are suited to identify preterm infants at risk. Our results emphasize the prenatal impact to the origins of BPD.

Fluctuations in Oxygen Saturation during Synchronized Nasal Intermittent Positive Pressure Ventilation and Nasal High-Frequency Oscillatory Ventilation in Very Low Birth Weight Infants: A Randomized Crossover Trial

BACKGROUND

Very low birth weight (VLBW) infants on noninvasive ventilation (NIV) experience frequent fluctuations in oxygen saturation (SpO2) that are associated with an increased risk for mortality and severe morbidities.

METHODS

In this randomized crossover trial, VLBW infants (n = 22) born 22+3 to 28+0 weeks on NIV with supplemental oxygen were allocated on two consecutive days in random order to synchronized nasal intermittent positive pressure ventilation (sNIPPV) and nasal high-frequency oscillatory ventilation (nHFOV) for 8 h. nHFOV and sNIPPV were set to equivalent mean airway pressure and transcutaneous pCO2. Primary outcome was the time spent within the SpO2 target (88-95%).

RESULTS

During sNIPPV, VLBW infants spent significantly more time within the SpO2 target (59.9%) than during nHFOV (54.6%). The proportion of time spent in hypoxemia (22.3% vs. 27.1%) and the mean fraction of supplemental oxygen (FiO2) (29.4% vs. 32.8%) were significantly reduced during sNIPPV, while the respiratory rate (50.1 vs. 42.6) was significantly higher. Mean SpO2, SpO2 above the target, number of prolonged (>1 min) and severe (SpO2 <80%) hypoxemic episodes, parameters of cerebral tissue oxygenation using NIRS, number of FiO2 adjustments, heart rate, number of bradycardias, abdominal distension and transcutaneous pCO2 did not differ between both interventions.

CONCLUSIONS

In VLBW infants with frequent fluctuations in SpO2, sNIPPV is more efficient than nHFOV to retain the SpO2 target and to reduce FiO2 exposure. These results demand more detailed investigations into cumulative oxygen toxicities during different modes of NIV over the weaning period, particularly with regard to consequences for long-term outcomes.

Respiratory and Intestinal Microbiota in Pediatric Lung Diseases-Current Evidence of the Gut-Lung Axis

The intestinal microbiota is known to influence local immune homeostasis in the gut and to shape the developing immune system towards elimination of pathogens and tolerance towards self-antigens. Even though the lung was considered sterile for a long time, recent evidence using next-generation sequencing techniques confirmed that the lower airways possess their own local microbiota. Since then, there has been growing evidence that the local respiratory and intestinal microbiota play a role in acute and chronic pediatric lung diseases. The concept of the so-called gut–lung axis describing the mutual influence of local microbiota on distal immune mechanisms was established. The mechanisms by which the intestinal microbiota modulates the systemic immune response include the production of short-chain fatty acids (SCFA) and signaling through pattern recognition receptors (PRR) and segmented filamentous bacteria. Those factors influence the secretion of pro- and anti-inflammatory cytokines by immune cells and further modulate differentiation and recruitment of T cells to the lung. This article does not only aim at reviewing recent mechanistic evidence from animal studies regarding the gut–lung axis, but also summarizes current knowledge from observational studies and human trials investigating the role of the respiratory and intestinal microbiota and their modulation by pre-, pro-, and synbiotics in pediatric lung diseases.

Compatibility of rapid enteral feeding advances and noninvasive ventilation in preterm infants-An observational study

AIM

To evaluate safety and clinical outcome of rapid enteral feeding advances in preterm infants <1500 g birthweight (BW).

METHODS

In this single-center retrospective cohort study, 293 preterm infants born during 2015-2018 were comparatively analyzed before (n = 145) and after (n = 148) the implementation of a rapid enteral feeding protocol with daily milk increments of 20-30 ml/kg of body weight. Major outcome parameters were focused toward pulmonary morbidities and nutritional variables.

RESULTS

Preterm infants in the rapid feeding advancement group were more successfully stabilized on noninvasive ventilation (p < 0.001) never requiring mechanical ventilation. Duration of respiratory support (0.465) and frequency of bronchopulmonary dysplasia (BPD) (p = 0.341) and severe BPD (0.273) did not differ between both groups. Furthermore, patients in the rapid feeding group achieved full volume feedings faster (p < 0.001), regained BW earlier (p = 0.009), and displayed significantly improved somatic growth at 36 weeks gestational age (p < 0.001). There was no increased risk for further morbidities of prematurity including feeding intolerance, necrotizing enterocolitis (NEC), and focal intestinal perforation.

CONCLUSION

Rapid enteral feeding advancements in preterm infants <1500 g BW are safe and do not impede stabilization on noninvasive ventilation.

When inflammation meets lung development-an update on the pathogenesis of bronchopulmonary dysplasia

Even more than 50 years after its initial description, bronchopulmonary dysplasia (BPD) remains one of the most important and lifelong sequelae following premature birth. Tremendous efforts have been undertaken since then to reduce this ever-increasing disease burden but a therapeutic breakthrough preventing BPD is still not in sight. The inflammatory response provoked in the immature lung is a key driver of distorted lung development and impacts the formation of alveolar, mesenchymal, and vascular structures during a particularly vulnerable time-period. During the last 5 years, new scientific insights have led to an improved pathomechanistic understanding of BPD origins and disease drivers. Within the framework of current scientific progress, concepts involving disruption of the balance of key inflammatory and lung growth promoting pathways by various stimuli, take center stage. Still today, the number of efficient therapeutics available to prevent BPD is limited to a few, well-established pharmacological interventions including postnatal corticosteroids, early caffeine administration, and vitamin A. Recent advances in the clinical care of infants in the neonatal intensive care unit (NICU) have led to improvements in survival without a consistent reduction in the incidence of BPD. Our update provides latest insights from both preclinical models and clinical cohort studies and describes novel approaches to prevent BPD.

Moving Bronchopulmonary Dysplasia Research from the Bedside to the Bench

Although advances in the respiratory management of extremely preterm infants have led to improvements in survival, this progress has not yet extended to a reduction in the incidence of bronchopulmonary dysplasia (BPD). BPD is a complex multifactorial condition that primarily occurs due to disturbances in the regulation of normal pulmonary airspace and vascular development. Preterm birth and exposure to invasive mechanical ventilation also compromises large airway development, leading to significant morbidity and mortality. Although both predisposing and protective genetic and environmental factors have been frequently described in the clinical literature, these findings have had limited impact on the development of effective therapeutic strategies. This gap is likely because the molecular pathways that underlie these observations are yet not fully understood, limiting the ability of researchers to identify novel treatments that can preserve normal lung development and/or enhance cellular repair mechanisms. In this review article, we will outline various well-established clinical observations whilst identifying key knowledge gaps that need to be filled with carefully designed pre-clinical experiments. We will address these issues by discussing controversial topics in the pathophysiology, the pathology and the treatment of BPD, including an evaluation of existing animal models that have been used to answer important questions.

Statistical inference for ordinal predictors in generalized additive models with application to Bronchopulmonary Dysplasia

Objective

Discrete but ordered covariates are quite common in applied statistics, and some regularized fitting procedures have been proposed for proper handling of ordinal predictors in statistical models. Motivated by a study from neonatal medicine on Bronchopulmonary Dysplasia (BPD), we show how quadratic penalties on adjacent dummy coefficients of ordinal factors proposed in the literature can be incorporated in the framework of generalized additive models, making tools for statistical inference developed there available for ordinal predictors as well.

Results

The approach presented allows to exploit the scale level of ordinally scaled factors in a sound statistical framework. Furthermore, several ordinal factors can be considered jointly without the need to collapse levels even if the number of observations per level is small. By doing so, results obtained earlier on the BPD data analyzed could be confirmed.

Oxygen Toxicity to the Immature Lung-Part I: Pathomechanistic Understanding and Preclinical Perspectives

In utero, the fetus and its lungs develop in a hypoxic environment, where HIF-1α and VEGFA signaling constitute major determinants of further development. Disruption of this homeostasis after preterm delivery and extrauterine exposure to high fractions of oxygen are among the key events leading to bronchopulmonary dysplasia (BPD). Reactive oxygen species (ROS) production constitutes the initial driver of pulmonary inflammation and cell death, altered gene expression, and vasoconstriction, leading to the distortion of further lung development. From preclinical studies mainly performed on rodents over the past two decades, the deleterious effects of oxygen toxicity and the injurious insults and downstream cascades arising from ROS production are well recognized. This article provides a concise overview of disease drivers and different therapeutic approaches that have been successfully tested within experimental models. Despite current studies, clinical researchers are still faced with an unmet clinical need, and many of these strategies have not proven to be equally effective in clinical trials. In light of this challenge, adapting experimental models to the complexity of the clinical situation and pursuing new directions constitute appropriate actions to overcome this dilemma. Our review intends to stimulate research activities towards the understanding of an important issue of immature lung injury.

Gut microbiota and bronchopulmonary dysplasia

Bronchopulmonary dysplasia is a relatively common and severe complication of prematurity, and its pathogenesis remains ambiguous. Revolutionary advances in microbiological analysis techniques, together with the growing sophistication of the gut-lung axis hypothesis, have resulted in more studies linking gut microbiota dysbiosis to the occurrence and development of bronchopulmonary dysplasia. The present article builds on current findings to examine the intrinsic associations between gut microbiota and bronchopulmonary dysplasia. Gut microbiota dysbiosis may insult the intestinal barrier, triggering inflammation, metabolic disturbances, and malnutrition, consequences of which might impact bronchopulmonary dysplasia by altering the gut-lung axis. By evaluating the potential mechanisms, new therapeutic targets and potential therapeutic modalities for bronchopulmonary dysplasia can be identified from a microecological perspective.

MSC Based Therapies to Prevent or Treat BPD-A Narrative Review on Advances and Ongoing Challenges

Bronchopulmonary dysplasia (BPD) remains one of the most devastating consequences of preterm birth resulting in life-long restrictions in lung function. Distorted lung development is caused by its inflammatory response which is mainly provoked by mechanical ventilation, oxygen toxicity and bacterial infections. Dysfunction of resident lung mesenchymal stem cells (MSC) represents one key hallmark that drives BPD pathology. Despite all progress in the understanding of pathomechanisms, therapeutics to prevent or treat BPD are to date restricted to a few drugs. The limited therapeutic efficacy of established drugs can be explained by the fact that they fail to concurrently tackle the broad spectrum of disease driving mechanisms and by the huge overlap between distorted signal pathways of lung development and inflammation. The great enthusiasm about MSC based therapies as novel therapeutic for BPD arises from the capacity to inhibit inflammation while simultaneously promoting lung development and repair. Preclinical studies, mainly performed in rodents, raise hopes that there will be finally a broadly acting, efficient therapy at hand to prevent or treat BPD. Our narrative review gives a comprehensive overview on preclinical achievements, results from first early phase clinical studies and challenges to a successful translation into the clinical setting.

Correlation of Early Nutritional Supply and Development of Bronchopulmonary Dysplasia in Preterm Infants <1,000 g

Background: Bronchopulmonary dysplasia (BPD) has multifactorial origins and is characterized by distorted physiological lung development. The impact of nutrition on the incidence of BPD is less studied so far. Methods: A retrospective single center analysis was performed on n = 207 preterm infants <1,000 g and <32 weeks of gestation without severe gastrointestinal complications to assess the impact of variations in nutritional supply during the first 2 weeks of life on the pulmonary outcome. Infants were grouped into no/mild and moderate/severe BPD to separate minor and major limitations in lung function. Results: After risk adjustment for gestational age, birth weight, sex, multiples, and antenatal steroids, a reduced total caloric intake and carbohydrate supply as the dominant energy source during the first 2 weeks of life prevailed statistically significant in infants developing moderate/severe BPD (p < 0.05). Enteral nutritional supply was increased at a slower rate with prolonged need for parenteral nutrition in the moderate/severe BPD group while breast milk provision and objective criteria of feeding intolerance were equally distributed in both groups. Conclusion: Early high caloric intake is correlated with a better pulmonary outcome in preterm infants <1,000 g. Our results are in line with the known strong impact of nutrient supply on somatic growth and psychomotor development. Our data encourage paying special attention to further decipher the ideal nutritional requirements for unrestricted lung development and promoting progressive enteral nutrition in the absence of objective criteria of feeding intolerance.