Early human milk feeding: Relationship to intestinal barrier maturation and postnatal growth.

OBJECTIVES: Early exposure to mother's own milk (MOM) promotes intestinal barrier maturation in preterm infants. We hypothesized (1) donor human milk (DHM) supplementation reduces intestinal permeability (IP) similar to exclusive MOM and (2) early HM exposure and low IP at 7-10 days postnatal age (PNA) are associated with improved growth outcomes. METHODS: IP was measured by the standard sugar absorption test (SAT) in infants <33 weeks gestation between 7-10 days PNA. Nutritional and anthropometric data were recorded. Postnatal growth failure (PNGF) was defined as a decrease in weight z-score >1 from birth to discharge to home. RESULTS: Of 158 preterm infants, the mean (SD) gestational age was 29.9(2.3) weeks and birthweight 1388(424) g. Diet prior to SAT was exclusive MOM [N = 55(35%)], DHM ± MOM [N = 52(33%)], or preterm formula±MOM [N = 51(32%)]. The mean Lactulose(La)/Rhamnose(Rh) ratio was lower in the exclusive MOM [0.06(0.07)] and DBM ± MOM [0.05(0.07)] groups compared to the preterm formula±MOM group [0.11(0.11)], p < 0.01). Cumulative intake >150 ml/kg MOM ± DHM, but not preterm formula within 7-10 days PNA was associated with early intestinal barrier maturation. Low IP was not associated with lower risk of PNGF at discharge. CONCLUSIONS: Low IP is associated with cumulative intake of MOM alone or supplemented with DHM > 150 ml/kg within 7-10 days PNA. CLINICAL TRIAL REGISTRATION: Clinicaltrials.gov NCT01756040 ; web link to study on registry: https://clinicaltrials.gov/study/NCT01756040 . IMPACT: Key message Early intestinal barrier maturation is associated with cumulative intake of exclusive MOM alone or supplemented with DHM > 150 ml/kg within 7-10 days after birth, but is not associated with lower risk of PNGF at time of discharge. What it adds to existing literature? This observational study is the first study to demonstrate that supplemental DHM promotes intestinal barrier maturation similar to MOM alone. What is the impact? The findings underscore the importance of early introduction of human milk feeds as MOM or MOM supplemented with DHM in sufficient volume to promote early intestinal barrier maturation.

Mice Expressing Cosegregating Single Nucleotide Polymorphisms (D298G and N397I) in TLR4 Have Enhanced Responses to House Dust Mite Allergen.

Asthma is a common and ubiquitous chronic respiratory disease that is associated with airway inflammation and hyperreactivity resulting in airway obstruction. It is now accepted that asthma is controlled by a combination of host genetics and environment in a rather complex fashion; however, the link between sensing of the environment and development and exacerbation of allergic lung inflammation is unclear. Human populations expressing cosegregating D299G and T399I polymorphisms in the TLR4 gene are associated with a decreased risk for asthma in adults along with hyporesponsiveness to inhaled LPS, the TLR4 ligand. However, these data do not account for other human genetic or environmental factors. Using a novel mouse strain that expresses homologous human TLR4 polymorphisms (TLR4-single nucleotide polymorphism [SNP]), we directly tested the effect of these TLR4 polymorphisms on in vivo responses to allergens using two models of induction. We report that intact TLR4 is required for allergic inflammation when using the OVA and LPS model of induction, as cellular and pathological benchmarks were diminished in both TLR4-SNP and TLR4-deficent mice. However, in the more clinically relevant model using house dust mite extract for induction, responses were enhanced in the TLR4-SNP mice, as evidenced by greater levels of eosinophilic inflammation, Th2 cytokine production, and house dust mite-specific IgG1 production compared with wild-type mice; however, mucus production and airway hyperreactivity were not affected. These results suggest that the TLR4 polymorphic variants (genes) interact differently with the allergic stimulation (environment).

Secretory-IgA binding to intestinal microbiota attenuates inflammatory reactions as the intestinal barrier of preterm infants matures.

Previous work has shown that Secretory-IgA (SIgA) binding to the intestinal microbiota is variable and may regulate host inflammatory bowel responses. Nevertheless, the impact of the SIgA functional binding to the microbiota remains largely unknown in preterm infants whose immature epithelial barriers make them particularly susceptible to inflammation. Here, we investigated SIgA binding to intestinal microbiota isolated from stools of preterm infants <33 weeks gestation with various levels of intestinal permeability. We found that SIgA binding to intestinal microbiota attenuates inflammatory reactions in preterm infants. We also observed a significant correlation between SIgA affinity to the microbiota and the infant's intestinal barrier maturation. Still, SIgA affinity was not associated with developing host defenses, such as the production of mucus and inflammatory calprotectin protein, but it depended on the microbiota shifts as the intestinal barrier matures. In conclusion, we reported an association between the SIgA functional binding to the microbiota and the maturity of the preterm infant's intestinal barrier, indicating that the pattern of SIgA coating is altered as the intestinal barrier matures.

Renal versus cerebral saturation trajectories: the perinatal transition in preterm neonates.

BACKGROUND: The aim of this study was to develop reference renal saturation (rSrO2) curves in premature infants, depict how they differ from cerebral saturation (rScO2) curves, and evaluate the effect of blood pressure on these values using near-infrared spectroscopy (NIRS). METHODS: This is a prospective cohort study of 57 inborn infants <12 h and <30 weeks gestation. rScO2, rSrO2, fractional tissue oxygen extraction (FTOE), and mean arterial blood pressure (MAP) were continuously monitored every 30 s for 96 h. Quantile regression was used to establish nomograms, and mean saturation values were evaluated for different MAP ranges. RESULTS: Median rSrO2 at the start of monitoring was ~10% higher than rScO2. rSrO2 showed a significant decline over time while rScO2 peaked at 26 h. FTOE demonstrated a similar but inverse trend to their saturation counterparts. rScO2 declined as MAP increased, while rSrO2 showed a peak and decline as MAP increased. CONCLUSIONS: We provide rSrO2 reference curves for the first 4 days of life, which differ in their trajectory from rScO2 and from what has previously been reported for rSrO2 in the full-term population. In addition, we observed a peak and decline in renal saturation with increasing MAP, suggesting a renovascular response to blood pressure changes. IMPACT: This article depicts reference renal saturation curves during the perinatal transition in preterm infants. We show how renal saturation compares to cerebral saturation trends over time. We describe a peak and decline in renal saturation with increasing MAP, suggesting a renovascular response to blood pressure changes.

Randomized trial of azithromycin to eradicate Ureaplasma respiratory colonization in preterm infants: 2-year outcomes.

BACKGROUND: To assess the potential impact of azithromycin treatment in the first week following birth on 2-year outcomes in preterm infants with and without Ureaplasma respiratory colonization who participated in a double-blind, placebo-controlled randomized controlled trial. METHODS: Respiratory morbidity was assessed at NICU discharge and at 6, 12, and 22-26 months corrected age using pulmonary questionnaires. Comprehensive neurodevelopmental assessments were completed between 22 and 26 months corrected age. The primary and secondary composite outcomes were death or severe respiratory morbidity and death or moderate-severe neurodevelopmental impairment, respectively, at 22-26 months corrected age. RESULTS: One hundred and twenty-one randomized participants (azithromycin, N = 60; placebo, N = 61) were included in the intent-to-treat analysis. There were no significant differences in death or serious respiratory morbidity (34.8 vs 30.4%, p = 0.67) or death or moderate-severe neurodevelopmental impairment (47 vs 33%, p = 0.11) between the azithromycin and placebo groups. Among all trial participants, tracheal aspirate Ureaplasma-positive infants experienced a higher frequency of death or serious respiratory morbidity at 22-26 months corrected age (58%) than tracheal aspirate Ureaplasma-negative infants (34%) or non-intubated infants (21%) (p = 0.028). CONCLUSIONS: We did not observe strong evidence of a difference in long-term pulmonary and neurodevelopment outcomes in preterm infants treated with azithromycin in the first week of life compared to placebo. IMPACT: No strong evidence of a difference in long-term pulmonary and neurodevelopment outcomes was identified at 22-26 months corrected age in infants treated with azithromycin in the first week of life compared to placebo. The RCT is the first study of 2-year pulmonary and neurodevelopmental outcomes of azithromycin treatment in ELGANs. Provides evidence that ELGANs with lower respiratory tract Ureaplasma have the most frequent serious respiratory morbidity in the first 2 years of life, suggesting that a Phase III trial of azithromycin to prevent BPD targeting this population is warranted.

Assessment of Neonatal Intensive Care Unit Sound Exposure Using a Smartphone Application.

OBJECTIVE: This study aimed to determine the impact of neonatal intensive care unit (NICU) design and environmental factors on neonatal sound exposures. We hypothesized that monitoring with a smartphone application would identify modifiable environmental factors in different NICU design formats. STUDY DESIGN: Minimum, maximum, and peak decibel (dB) recordings were obtained using the Decibel X phone app, and the presence of noise sources was recorded in each patient space at three NICUs over a 6-month period (December 2017 to May 2018). Data were analyzed by Student's t-test and ANOVA with Bonferroni correction. Data were collected at the University of Maryland Medical Center single family room (SFR) level IV and St. Agnes Healthcare hybrid pod/single family room level III NICU, Baltimore, MD and at Prince George's Hospital Center open-pod design Level III NICU, Cheverly, MD. RESULTS: All recordings in the three NICUs exceeded the American Academy of Pediatrics (AAP) recommended <45 dB level. The maximum and peak dB were highest in the open pod format level III NICU. Conversations/music alone and combined with other factors contributed to increased sound exposure. Sound exposure varied by day/night shift, with higher day exposures at the level III hybrid and open pod NICUs and higher night exposures at the level IV SFR NICU. CONCLUSION: Although sound exposure varied by NICU design, all recordings exceeded the AAP recommendation due, in part, to potentially modifiable environmental factors. A smartphone application may be useful for auditing NICU sound exposure in quality improvements efforts to minimize environmental sound exposure. KEY POINTS: · Smartphone application was used to assess NICU sound exposure.. · All cases of sound exposure exceed recommendations.. · A smartphone application was used to identify modifiable factors..

Intestinal Barrier Maturation in Very Low Birthweight Infants: Relationship to Feeding and Antibiotic Exposure.

OBJECTIVE: To test the hypothesis that feeding and antibiotic exposures affect intestinal barrier maturation in preterm infants, we serially measured intestinal permeability (IP) biomarkers in infants <33 weeks gestation (gestational age [GA]) during the first 2 weeks of life. STUDY DESIGN: Eligible infants <33 weeks GA were enrolled within 4 days of birth in a prospective study of IP biomarkers (NCT01756040). Study participants received the nonmetabolized sugars lactulose/rhamnose enterally on study days 1, 8, and 15 and lactulose/rhamnose were measured in urine by high-performance liquid chromatography. Serum zonulin and fecal alpha-1-anti-trypsin, 2 other IP markers, were measured by semiquantitative Western blot and ELISA, respectively. RESULTS: In a cohort of 43 subjects, the lactulose/rhamnose ratio was increased on day 1 and decreased over 2 weeks, but remained higher in infants born at ≤28 weeks of gestation compared with IP in infants born at >28 weeks of gestation. Exclusive breastmilk feeding was associated with more rapid maturation in intestinal barrier function. A cluster analysis of 35 subjects who had urine samples from all time points revealed 3 IP patterns (cluster 1, normal maturation: n = 20 [57%]); cluster 2, decreased IP during the first week and subsequent substantial increase: n = 5 [14%]); and cluster 3, delayed maturation: n = 10 [29%]). There were trends toward more prolonged antibiotic exposure (P = .092) and delayed initiation of feeding ≥4 days (P = .064) in infants with abnormal IP patterns. CONCLUSIONS: Intestinal barrier maturation in preterm infants is GA and postnatal age dependent, and is influenced by feeding with a maturational effect of breastmilk feeding and possibly by antibiotic exposures. TRIAL REGISTRATION: ClinicalTrials.gov: NCT01756040.

Pharmacokinetics, microbial response, and pulmonary outcomes of multidose intravenous azithromycin in preterm infants at risk for Ureaplasma respiratory colonization.

The study objectives were to refine the population pharmacokinetics (PK) model, determine microbial clearance, and assess short-term pulmonary outcomes of multiple-dose azithromycin treatment in preterm infants at risk for Ureaplasma respiratory colonization. Fifteen subjects (7 of whom were Ureaplasma positive) received intravenous azithromycin at 20 mg/kg of body weight every 24 h for 3 doses. Azithromycin concentrations were determined in plasma samples obtained up to 168 h post-first dose by using a validated liquid chromatography-tandem mass spectrometry method. Respiratory samples were obtained predose and at three time points post-last dose for Ureaplasma culture, PCR, antibiotic susceptibility testing, and cytokine concentration determinations. Pharmacokinetic data from these 15 subjects as well as 25 additional subjects (who received either a single 10-mg/kg dose [n = 12] or a single 20-mg/kg dose [n = 13]) were analyzed by using a nonlinear mixed-effect population modeling (NONMEM) approach. Pulmonary outcomes were assessed at 36 weeks post-menstrual age and 6 months adjusted age. A 2-compartment model with all PK parameters allometrically scaled on body weight best described the azithromycin pharmacokinetics in preterm neonates. The population pharmacokinetics parameter estimates for clearance, central volume of distribution, intercompartmental clearance, and peripheral volume of distribution were 0.15 liters/h · kg(0.75), 1.88 liters · kg, 1.79 liters/h · kg(0.75), and 13 liters · kg, respectively. The estimated area under the concentration-time curve over 24 h (AUC24)/MIC90 value was ∼ 4 h. All posttreatment cultures were negative, and there were no drug-related adverse events. One Ureaplasma-positive infant died at 4 months of age, but no survivors were hospitalized for respiratory etiologies during the first 6 months (adjusted age). Thus, a 3-day course of 20 mg/kg/day intravenous azithromycin shows preliminary efficacy in eradicating Ureaplasma spp. from the preterm respiratory tract.

Azithromycin to prevent bronchopulmonary dysplasia in ureaplasma-infected preterm infants: pharmacokinetics, safety, microbial response, and clinical outcomes with a 20-milligram-per-kilogram single intravenous dose.

Ureaplasma respiratory tract colonization is associated with bronchopulmonary dysplasia (BPD) in preterm infants. Previously, we demonstrated that a single intravenous (i.v.) dose of azithromycin (10 mg/kg of body weight) is safe but inadequate to eradicate Ureaplasma spp. in preterm infants. We performed a nonrandomized, single-arm open-label study of the pharmacokinetics (PK) and safety of intravenous 20-mg/kg single-dose azithromycin in 13 mechanically ventilated neonates with a gestational age between 24 weeks 0 days and 28 weeks 6 days. Pharmacokinetic data from 25 neonates (12 dosed with 10 mg/kg i.v. and 13 dosed with 20 mg/kg i.v.) were analyzed using a population modeling approach. Using a two-compartment model with allometric scaling of parameters on body weight (WT), the population PK parameter estimates were as follows: clearance, 0.21 liter/h × WT(kg)(0.75) [WT(kg)(0.75) indicates that clearance was allometrically scaled on body weight (in kilograms) with a fixed exponent of 0.75]; intercompartmental clearance, 2.1 liters/h × WT(kg)(0.75); central volume of distribution (V), 1.97 liters × WT (kg); and peripheral V, 17.9 liters × WT (kg). There was no evidence of departure from dose proportionality in azithromycin exposure over the tested dose range. The calculated area under the concentration-time curve over 24 h in the steady state divided by the MIC90 (AUC24/MIC90) for the single dose of azithromycin (20 mg/kg) was 7.5 h. Simulations suggest that 20 mg/kg for 3 days will maintain azithromycin concentrations of >MIC50 of 1 µg/ml for this group of Ureaplasma isolates for ≥ 96 h after the first dose. Azithromycin was well tolerated with no drug-related adverse events. One of seven (14%) Ureaplasma-positive subjects and three of six (50%) Ureaplasma-negative subjects developed physiologic BPD. Ureaplasma was eradicated in all treated Ureaplasma-positive subjects. Simulations suggest that a multiple-dose regimen may be efficacious for microbial clearance, but the effect on BPD remains to be determined.

IL-18R1 and IL-18RAP SNPs may be associated with bronchopulmonary dysplasia in African-American infants.

INTRODUCTION: The genetic contribution to the development of bronchopulmonary dysplasia (BPD) in prematurely born infants is substantial, but information related to the specific genes involved is lacking. RESULTS: Genotype analysis revealed, after multiple comparisons correction, two significant single-nucleotide polymorphism (SNPs), rs3771150 (IL-18RAP) and rs3771171 (IL-18R1), in African Americans (AAs) with BPD (vs. AAs without BPD; q < 0.05). No associations with Caucasian (CA) BPD, AA or CA respiratory distress syndrome (RDS), or prematurity in either AAs or CAs were identified with these SNPs. Respective frequencies were 0.098 and 0.093 in infants without BPD and 0.38 for each SNP in infants with BPD. In the replication set (82 cases; 102 controls), the P values were 0.012 for rs3771150 and 0.07 for rs3771171. Combining P values using Fisher's method, overall P values were 8.31 × 10(-7) for rs3771150 and 6.33 × 10(-6) for rs3771171. DISCUSSION: We conclude that IL-18RAP and IL-18R1 SNPs identify AA infants at risk for BPD. These genes may contribute to AA BPD pathogenesis via inflammatory-mediated processes and require further study. METHODS: We conducted a case-control SNP association study of candidate genes (n = 601) or 6,324 SNPs in 1,091 prematurely born infants with gestational age <35 weeks, with or without neonatal lung disease including BPD. BPD was defined as a need for oxygen at 28 days.

Altered Gut Microbiome and Fecal Immune Phenotype in Early Preterm Infants With Leaky Gut.

Intestinal barrier immaturity, or "leaky gut", is the proximate cause of susceptibility to necrotizing enterocolitis in preterm neonates. Exacerbated intestinal immune responses, gut microbiota dysbiosis, and heightened barrier injury are considered primary triggers of aberrant intestinal maturation in early life. Inordinate host immunity contributes to this process, but the precise elements remain largely uncharacterized, leaving a significant knowledge gap in the biological underpinnings of gut maturation. In this study, we investigated the fecal cytokine profile and gut microbiota in a cohort of 40 early preterm infants <33-weeks-gestation to identify immune markers of intestinal barrier maturation. Three distinct microbiota types were demonstrated to be differentially associated with intestinal permeability (IP), maternal breast milk feeding, and immunological profiles. The Staphylococcus epidermidis- and Enterobacteriaceae-predominant microbiota types were associated with an elevated IP, reduced breast milk feeding, and less defined fecal cytokine profile. On the other hand, a lower IP was associated with increased levels of fecal IL-1α/ß and a microbiota type that included a wide array of anaerobes with expanded fermentative capacity. Our study demonstrated the critical role of both immunological and microbiological factors in the early development of intestinal barrier that collectively shape the intestinal microenvironment influencing gut homeostasis and postnatal intestinal maturation in early preterm newborns.

Highly Specialized Carbohydrate Metabolism Capability in Bifidobacterium Strains Associated with Intestinal Barrier Maturation in Early Preterm Infants.

"Leaky gut," or high intestinal barrier permeability, is common in preterm newborns. The role of the microbiota in this process remains largely uncharacterized. We employed both short- and long-read sequencing of the 16S rRNA gene and metagenomes to characterize the intestinal microbiome of a longitudinal cohort of 113 preterm infants born between 240/7 and 326/7 weeks of gestation. Enabled by enhanced taxonomic resolution, we found that a significantly increased abundance of Bifidobacterium breve and a diet rich in mother's breastmilk were associated with intestinal barrier maturation during the first week of life. We combined these factors using genome-resolved metagenomics and identified a highly specialized genetic capability of the Bifidobacterium strains to assimilate human milk oligosaccharides and host-derived glycoproteins. Our study proposes mechanistic roles of breastmilk feeding and intestinal microbial colonization in postnatal intestinal barrier maturation; these observations are critical toward advancing therapeutics to prevent and treat hyperpermeable gut-associated conditions, including necrotizing enterocolitis (NEC). IMPORTANCE Despite improvements in neonatal intensive care, necrotizing enterocolitis (NEC) remains a leading cause of morbidity and mortality. "Leaky gut," or intestinal barrier immaturity with elevated intestinal permeability, is the proximate cause of susceptibility to NEC. Early detection and intervention to prevent leaky gut in "at-risk" preterm neonates are critical for decreasing the risk of potentially life-threatening complications like NEC. However, the complex interactions between the developing gut microbial community, nutrition, and intestinal barrier function remain largely uncharacterized. In this study, we reveal the critical role of a sufficient breastmilk feeding volume and the specialized carbohydrate metabolism capability of Bifidobacterium in the coordinated postnatal improvement of the intestinal barrier. Determining the clinical and microbial biomarkers that drive the intestinal developmental disparity will inform early detection and novel therapeutic strategies to promote appropriate intestinal barrier maturation and prevent NEC and other adverse health conditions in preterm infants.

NICU admission hypothermia, chorioamnionitis, and cytokines.

OBJECTIVE: To determine whether neonatal intensive care unit (NICU) admission hypothermia is associated with an intrauterine inflammatory response. METHODS: We analyzed a cohort of 309 very low birthweight infants to determine relationships between admission hypothermia, chorioamnionitis, and serum and cerebrospinal fluid (CSF) interleukin (IL)-1ß, IL-6, and tumor necrosis factor-α. RESULTS: Admission hypothermia <36°C occurred in 72% of patients <26 weeks and 44% of patients ≥26 weeks gestational age. NICU admission hypothermia was not associated with histologic chorioamnionitis or with elevated serum cytokine concentrations. CSF IL-6 concentrations ≥6.3 pg/mL were associated with admission hypothermia in infants <26 weeks' gestation. Clinical chorioamnionitis was associated with a lower risk of admission hypothermia, while cesarean section delivery was associated with increased risk. CONCLUSIONS: NICU admission hypothermia is common among preterm infants and is not associated with the fetal inflammatory response syndrome. Hypothermia is less common in the setting of clinical chorioamnionitis and more common in cesarean section deliveries, identifying two groups in whom extra attention to appropriate thermoregulation is warranted.

Point-of-Care Ultrasound to Confirm Umbilical Line Placement: Impact of a Simulation Enhanced Curriculum on Neonatal Intensive Care Unit Provider Competency.

INTRODUCTION: Neonatal intensive care unit (NICU) provider point-of-care ultrasound (POCUS) procedural competency for umbilical line placement confirmation has not been defined, and the necessary training to achieve competency has not been previously studied. This study's objective was to test the hypothesis that a simulation-enhanced curriculum will improve NICU providers' POCUS competency to confirm umbilical line placement. METHODS: Neonatal intensive care unit providers without prior ultrasound experience were randomized to a curriculum with or without simulation-based training. Competency for catheter detection, tip localization, and scan interpretation on patients was determined using learning curve-cumulative summation, a specific statistical tool designed to indicate when a predefined level of performance is reached. Differences in success rates were analyzed by χ2 test. RESULTS: Two thirds (22/33) of participants completed 10 scans. Three (simulation) and 1 (control) attained catheter detection competency (P = 0.28). The simulation group was more successful for catheter detection (81% vs. 69%, P = 0.04) and scan interpretation (61% vs. 48%, P = 0.04). Success did not differ by umbilical vessel location, provider role, or duration of NICU experience. CONCLUSIONS: A simulation-enhanced POCUS curriculum improved catheter detection rate and scan interpretation, but there was no difference in procedural competency between groups on ultrasound scans performed on patients with umbilical catheters. We speculate that more than 10 scans may be needed for NICU providers to obtain POCUS competency.

Surfactant protein-A limits Ureaplasma-mediated lung inflammation in a murine pneumonia model.

Ureaplasma respiratory tract colonization stimulates prolonged, dysregulated inflammation in the lungs of preterm infants, contributing to bronchopulmonary dysplasia (BPD) pathogenesis. Surfactant protein-A (SP-A), a lung collectin critical for bacterial clearance and regulating inflammation, is deficient in the preterm lung. To analyze the role of SP-A in modulating Ureaplasma-mediated lung inflammation, SP-A deficient (SP-A-/-) and WT mice were inoculated intratracheally with a mouse-adapted U. parvum isolate and indices of inflammation were sequentially assessed up to 28 d postinoculation. Compared with infected WT and noninfected controls, Ureaplasma-infected SP-A-/- mice exhibited an exaggerated inflammatory response evidenced by rapid influx of neutrophils and macrophages into the lung, and higher bronchoalveolar lavage TNF-alpha, mouse analogue of human growth-related protein alpha (KC), and monocyte chemotactic factor (MCP-1) concentrations. However, nitrite generation in response to Ureaplasma infection was blunted at 24 h and Ureaplasma clearance was delayed in SP-A-/- mice compared with WT mice. Coadministration of human SP-A with the Ureaplasma inoculum to SP-A-/- mice reduced the inflammatory response, but did not improve the bacterial clearance rate. SP-A deficiency may contribute to the prolonged inflammatory response in the Ureaplasma-infected preterm lung, but other factors may contribute to the impaired Ureaplasma clearance.

Cerebral autoregulation in premature infants during the first 96 hours of life and relationship to adverse outcomes.

OBJECTIVE: To test the hypothesis that impaired cerebral autoregulation (ICA) increases the susceptibility of premature infants to adverse outcomes, we determined the relationship of ICA and cerebral reactivity (CR) measured in the first 96 hours of life to the outcome of grade 3 or 4 intraventricular haemorrhage (IVH) and/or death within 1 month. SETTING: Single-centre level IV neonatal intensive care unit. PATIENTS: Neonates 24-29 weeks' gestation less than 12 hours old with invasive blood pressure monitoring. DESIGN: Cerebral saturations and mean arterial blood pressure were recorded every 30 s for 96 hours. For each 10 min epoch, the correlation coefficient (r) was calculated for mean arterial blood pressure versus cerebral saturations. The epoch was considered to have ICA if r>0.5 and CR if r<0. RESULTS: Sixty-one subjects were included. During the first 96 hours, ICA occurred 17.6% and CR occurred 41% of recorded time. In those without adverse outcomes, ICA decreased and CR increased by postnatal day (p<0.05). Adjusted for birth weight and gestational age, those with IVH and those who died spent more time with ICA and less time with CR (p<0.05) over the entire recording period. Those with IVH had 1.5-fold increase in time with ICA on day 2 (p=0.021), and decrease in time with CR on day 3 (p=0.036). Compared with survivors, non-survivors spent more time with ICA on days 3 and 4 (p<0.005), and less with CR on day 3 (p=0.032). CONCLUSION: ICA and CR vary by postnatal day and these patterns are associated with adverse outcomes.

Microbial Biomarkers of Intestinal Barrier Maturation in Preterm Infants.

Intestinal barrier immaturity, or "leaky gut," is the proximate cause of susceptibility to necrotizing enterocolitis in preterm neonates. However, the impact of intestinal microbiota development on intestinal mucosal barrier maturation has not been evaluated in this population. In this study, we investigated a longitudinally sampled cohort of 38 preterm infants < 33 weeks gestation monitored for intestinal permeability (IP) and fecal microbiota during the first 2 weeks of life. Rapid decrease in IP indicating intestinal barrier function maturation correlated with significant increase in community diversity. In particular, members of the Clostridiales and Bifidobacterium were highly transcriptionally active, and progressively increasing abundance in Clostridiales was significantly associated with decreased intestinal permeability. Further, neonatal factors previously identified to promote intestinal barrier maturation, including early exclusive breastmilk feeding and shorter duration antibiotic exposure, associate with the early colonization of the intestinal microbiota by members of the Clostridiales, which altogether are associated with improved intestinal barrier function in preterm infants.

The Objective Use of Pulse Oximetry to Predict Respiratory Support Transition in Preterm Infants: An Observational Pilot Study.

BACKGROUND: Preterm infants often require some form of respiratory support with supplemental oxygen and are monitored by continuous pulse oximetry (SpO2 ). The study objective was to determine whether the histogram distribution of SpO2 over a 24-h period will predict readiness for weaning respiratory support in preterm infants. We hypothesize that infants with ≥15% of time spent with SpO2 <86% before transitioning from CPAP or high-flow nasal cannula (HFNC) to low-flow nasal cannula, oxyhood, or room air are more likely to fail transitioning. METHODS: The SpO2 histograms were downloaded daily for 31 infants, 24-32 weeks gestational age, before transition from CPAP or HFNC to low-flow nasal cannula, oxyhood, or room air. The SpO2 histogram downloads were continued for each infant for 1 week after transition or when the infant reached 36 weeks postmenstrual age or when SpO2 monitoring was discontinued. Failure was defined as an increase in respiratory support within 72 h of transitioning. We compared the percentage of time for each SpO2 quintile for the 24-h periods before and immediately following CPAP/HFNC transitioning between groups. RESULTS: Twenty-four subjects transitioned successfully, but 7 subjects failed. Two of 7 subjects (28.6%) who failed transition experienced SpO2 <86% ≥15% of the time pretransition compared with none in the success group (P = .045). The failure group experienced SpO2 <86% 10.7 ± 11.9% of time pre-wean compared with 3.3 ± 4.7% of time in the success group (P = .02). In contrast, infants who were successfully weaned tended to experience a greater percentage of time with SpO2 >95% compared with the failure group, both pre-wean (54.3 ± 36.1% vs. 33 ± 27.7%, P = .16) and post-wean (52 ± 35.4% vs. 27.4 ± 27.7%, P = .10). CONCLUSIONS: These data suggest that pulse oximetry histograms may be useful in assessing CPAP/HFNC support transition readiness.

Enhanced allergic responsiveness after early childhood infection with respiratory viruses: Are long-lived alternatively activated macrophages the missing link?

Early childhood infection with respiratory viruses, including human rhinovirus, respiratory syncytial virus (RSV) and influenza, is associated with an increased risk of allergic asthma and severe exacerbation of ongoing disease. Despite the long recognition of this relationship, the mechanism linking viral infection and later susceptibility to allergic lung inflammation is still poorly understood. We discuss the literature and provide new evidence demonstrating that these viruses induce the alternative activation of macrophages. Alternatively activated macrophages (AAM) induced by RSV or influenza infection persisted in the lungs of mice up to 90 days after initial viral infection. Several studies suggest that AAM contribute to allergic inflammatory responses, although their mechanism of action is unclear. In this commentary, we propose that virus-induced AAM provide a link between viral infection and enhanced responses to inhaled allergens.