The Neonatal Microbiome and Necrotizing Enterocolitis.

Necrotizing enterocolitis (NEC) is a devastating disorder that affects approximately 10% of premature infants. Its mortality remains high (15-30%), and its cause remains unknown. About 80% of cases occur within 35 days of birth among hospitalized newborns of low birth weight. Probiotics diminish the incidence and severity of NEC, and NEC does not occur antepartum. NEC affects a readily identifiable at-risk group, has a tightly defined interval before its onset, occurs in an organ system that is intimately associated with a microbial population in flux, has a plausible association with the intestinal microbiota, and cohorts at risk have rarely been studied in large numbers, or prospectively. This disorder, therefore, provides a unique opportunity to explore the role of the human enteric microbiome in a devastating disease. Moreover, NEC epidemiology and age-incidence present an ability to enroll and study cohorts that are highly likely to provide valuable pathophysiologic and microbiologic insights.

In this project, we will identify and quantify the microbial components of stool and its products before and at the onset of NEC. In doing so, we will test the overarching hypothesis that NEC is a direct or indirect consequence of the enteric biomass, its products, or both. We will use multicenter cohorts of premature infants at high risk of developing NEC, extend our research on this disease currently sponsored by the Washington University Institute of Clinical and Translational Sciences, and continue our longstanding collaborations with the Genome Center at Washington University and the Washington University Digestive Diseases Research Core Center (Informatics Core). The Aims of this proposal are to (1) conduct a case cohort study in which we compare clinical data and biological specimens from cases and well-matched controls; (2) determine if the kind and density of intestinal biomass, its gene content, and transcriptional activity are associated with, and potential determinants of, NEC; and (3) determine if host risk alleles for intestinal inflammation play a role in the development of NEC. These efforts will be accomplished using subjects from three collaborating neonatal intensive care units (NICUs), focusing on the critical, instructive, and understudied pre-NEC stage of illness, and formulating a data repository that will be a resource for investigators worldwide who wish to focus their efforts on NEC, its precipitants, and its prevention and cure.
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Impact of neonatal intensive care bed configuration on rates of late-onset bacterial sepsis and methicillin-resistant Staphylococcus aureus colonization

OBJECTIVES: Infections cause significant morbidity and mortality in neonatal intensive care units (NICUs). The association between nursery design and nosocomial infections has not been delineated. We hypothesized that rates of colonization by methicillin-resistant Staphylococcus aureus (MRSA), late-onset sepsis, and mortality are reduced in single-patient rooms. DESIGN: Retrospective cohort study. SETTING: NICU in a tertiary referral center. METHODS: Our NICU is organized into single-patient and open-unit rooms. Clinical datasets including bed location and microbiology results were examined over a 29-month period. Differences in outcomes between bed configurations were determined by Chi-square and Cox regression. PATIENTS: All NICU patients. RESULTS: Among 1823 patients representing 55,166 patient-days, single-patient and open-unit models had similar incidences of MRSA colonization and MRSA colonization-free survival times. Average daily census was associated with MRSA colonization rates only in single-patient rooms (hazard ratio 1.31, p=0.039), while hand hygiene compliance on room entry and exit was associated with lower colonization rates independent of bed configuration (hazard ratios 0.834 and 0.719 per 1% higher compliance, respectively). Late-onset sepsis rates were similar in single-patient and open-unit models as were sepsis-free survival and the combined outcome of sepsis or death. After controlling for demographic, clinical and unit-based variables, multivariate Cox regression demonstrated that bed configuration had no effect on MRSA colonization, late-onset sepsis, or mortality. CONCLUSIONS: MRSA colonization rate was impacted by hand hygiene compliance, regardless of room configuration, while average daily census only affected infants in single-patient rooms. Single-patient rooms did not reduce the rates of MRSA colonization, late-onset sepsis or death

Sequencing of idiopathic pulmonary fibrosis-related genes reveals independent single gene associations

BACKGROUND: Previous studies investigating a genetic basis for idiopathic pulmonary fibrosis (IPF) have focused on resequencing single genes in IPF kindreds or cohorts to determine the genetic contributions to IPF. None has investigated interactions among the candidate genes. OBJECTIVE: To compare the frequencies and interactions of mutations in six IPF-associated genes in a cohort of 132 individuals with IPF with those of a disease-control cohort of 192 individuals with chronic obstructive pulmonary disease (COPD) and the population represented in the Exome Variant Server. METHODS: We resequenced the genes encoding surfactant proteins A2 (SFTPA2), and C (SFTPC), the ATP binding cassette member A3 (ABCA3), telomerase (TERT), thyroid transcription factor (NKX2-1) and mucin 5B (MUC5B) and compared the collapsed frequencies of rare (minor allele frequency <1%), computationally predicted deleterious variants in each cohort. We also genotyped a common MUC5B promoter variant that is over-represented in individuals with IPF. RESULTS: We found 15 mutations in 14 individuals (11%) in the IPF cohort: (SFTPA2 (n=1), SFTPC (n=5), ABCA3 (n=4) and TERT (n=5)). No individual with IPF had two different mutations, but one individual with IPF was homozygous for p.E292V, the most common ABCA3 disease-causing variant. We did not detect an interaction between any of the mutations and the MUC5B promoter variant. CONCLUSIONS: Rare mutations in SFTPA2, SFTPC and TERT are collectively over-represented in individuals with IPF. Genetic analysis and counselling should be considered as part of the IPF evaluation

Left ventricle phenotyping utilizing tissue doppler imaging in premature infants with varying severity of bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) is characterized by alveolar-capillary simplification and is associated with pulmonary hypertension (PH) in preterm infants. The contribution of left ventricle (LV) disease towards this severe BPD-PH phenotype is not well established. We aimed to describe the longitudinal trajectory of the LV function as measured by tissue Doppler imaging (TDI) and its association with BPD-PH. We retrospectively assessed prospectively acquired clinical and echocardiographic data from 77 preterm infants born between 2011 and 2013. We characterized the LV function by measuring systolic and diastolic myocardial velocities (s\u27, e\u27, a\u27), isovolumetric relaxation time (IVRT), and myocardial performance index with TDI at three time periods from 32 and 36 weeks, postmenstrual age through one year of age. We also measured post systolic motion (PSM), a marker of myocardial dysfunction that results from asynchronous movement of the ventricular walls, and not previously described in preterm infants. Patients were stratified into groups according to BPD severity and the presence of PH and compared over time. Conventional TDI measures of the LV function were similar between groups, but the septal PSM was significantly prolonged over the first year of age in patients with BPD-PH. PSM provides a novel objective way to assess the hemodynamic impact of lung and pulmonary vascular disease severity on LV function in preterm infants with BPD and PH

Cardiac performance in the first year of age among preterm infants fed maternal breast milk

Importance: There is a beneficial association between human breast milk exposure in the neonatal period and cardiac mechanics in adults who were born preterm. It is unknown whether this benefit is apparent in infants in the first year of age. Objective: To test the hypothesis that higher consumption of mother\u27s own milk in preterm infants is associated with enhanced cardiac performance during the first year of age. Design, Setting, and Participants: This cross-sectional study of cardiac and nutritional data at an academic medical center included 80 individuals born preterm and 100 individuals in the control group born full-term. All births were between 2011 and 2013. Two-dimensional echocardiograms were performed at 32 weeks\u27 and 36 weeks\u27 postmenstrual age and at 1 year\u27s corrected age in individuals born preterm and at 1 month and 1 year of age in individuals born full-term. Statistical analysis was performed from January to May 2021. Exposures: Consumption of mother\u27s own milk. Main Outcomes and Measures: Main study outcomes included echocardiography measures of right and left ventricle longitudinal strain (function), left ventricle mass index and right ventricular areas (morphology), and pulmonary vascular resistance (pulmonary hemodynamics) at age 1 year. Results: Of 180 infants included in the study, 97 (54%) were Black infants and 89 (49%) were female infants. Among the 80 infants born in the preterm cohort, 43 (54%) were female infants and 43 (54%) were Black infants. The median gestational age at birth of the preterm infants was 27.0 weeks (interquartile range, 26.0-28.0 weeks) and the median birth weight was 960 g (interquartile range, 800-1138). For each week of exposure to mother\u27s own milk, preterm infants had greater magnitudes of right ventricular strain (eg, right longitudinal strain: β, 0.021; 95% CI, 0.002-0.041; P \u3c .001) and left ventricular strain (eg, left longitudinal strain: β, 0.065; 95% CI, 0.049-0.080; P = .01), larger right ventricle areas (eg, systolic area: β, 0.026; 95% CI, 0.011-0.042; P = .009), larger left ventricle mass index (β, 0.045; 95% CI, 0.024-0.073; P = .003), and decreased pulmonary vascular resistance (eg, pulmonary artery acceleration time: β, 0.041; 95% CI, 0.018-0.063; P \u3c .001) at 1 year\u27s corrected age, even after accounting for gestational age and common neonatal morbidities. Cardiac values approached those seen in controls born full-term with increased mother\u27s own milk exposure. There were no differences in any of the cardiac indices at 32 weeks\u27 postmenstrual age, but with each week of exposure, right ventricle function (eg, right longitudinal strain: β, 0.016; 95% CI, 0.002-0.031; P \u3c .001) was greater and pulmonary pressured (eg, pulmonary artery acceleration time: β, 0.0032; 95% CI, 0.0013-0.0062; P \u3c .001). Conclusions and Relevance: This study found that preterm infants with higher consumption of mother\u27s own milk had enhanced cardiac performance at age 1 year, suggesting that mother\u27s own milk consumption may play a dynamic modulator role on cardiac mechanics in preterm-born infants and help in normalization of the preterm cardiac phenotype

Maturational patterns of left ventricular rotational mechanics in pre-term infants through 1 year of age

BACKGROUND: Pre-mature birth impacts left ventricular development, predisposing this population to long-term cardiovascular risk. The aims of this study were to investigate maturational changes in rotational properties from the neonatal period through 1 year of age and to discern the impact of cardiopulmonary complications of pre-maturity on these measures. METHODS: Pre-term infants (\u3c29 weeks at birth, n = 117) were prospectively enrolled and followed to 1-year corrected age. Left ventricular basal and apical rotation, twist, and torsion were measured by two-dimensional speckle-tracking echocardiography and analysed at 32 and 36 weeks post-menstrual age and 1-year corrected age. A mixed random effects model with repeated measures analysis was used to compare rotational mechanics over time. Torsion was compared in infants with and without complications of cardiopulmonary diseases of pre-maturity, specifically bronchopulmonary dysplasia, pulmonary hypertension, and patent ductus arteriosus. RESULTS: Torsion decreased from 32 weeks post-menstrual age to 1-year corrected age in all pre-term infants (p \u3c 0.001). The decline from 32 to 36 weeks post-menstrual age was more pronounced in infants with cardiopulmonary complications, but was similar to healthy pre-term infants from 36 weeks post-menstrual age to 1-year corrected age. The decline was due to directional and magnitude changes in apical rotation over time (p \u3c 0.05). CONCLUSION: This study tracks maturational patterns of rotational mechanics in pre-term infants and reveals torsion declines from the neonatal period through 1 year. Cardiopulmonary diseases of pre-maturity may negatively impact rotational mechanics during the neonatal period, but the myocardium recovers by 1-year corrected age

A disorder of surfactant metabolism without identified genetic mutations

BACKGROUND: Surfactant metabolism disorders may result in diffuse lung disease in children. CASE PRESENTATION: We report a 3-years-old boy with dry cough, progressive hypoxemia, dyspnea and bilateral ground glass opacities at chest high-resolution computed tomography (HRCT) who had no variants in genes encoding surfactant proteins or transcription factors. Lung histology strongly suggested an abnormality of surfactant protein. A 7-month course of pulse intravenous high-dose methylprednisolone plus oral hydroxychloroquine and azithromycin led to gradual weaning from oxygen and oral steroids, and to improvement of cough and dyspnea. Over the follow-up period, hydroxychloroquine and azithromycin were not withdrawn as cough and dyspnea re-appeared at each attempt and disappeared at re-start. At 6 years of age chest HRCT still appeared unchanged, but clinical symptoms or signs were absent. CONCLUSIONS: In children suspected of inborn errors of pulmonary surfactant metabolism who do not have a recognized genetic mutation, lung biopsy with consistent histology may help physicians to address the definitive diagnosis