Shinya Oue

Association of gastric fluid microbes at birth with severe bronchopulmonary dysplasia.

Objective: Gastric fluid microbes were examined in preterm infants at birth to assess their influence on the postnatal outcome. Study design: Prospective cohort study. Setting: Level III neonatal intensive care unit. Patients: A total of 103 premature neonates with a gestational age of less than 32 weeks. Main outcome measure: Gastric fluid microbes were identified by analysis of bacterial 16S ribosomal RNA gene. Additionally, the urease gene of Ureaplasma species was detected by polymerase chain reaction of gastric fluid obtained at birth and/or tracheal aspirate from ventilated preterm infants. The association between detection of microbes and bronchopulmonary dysplasia was investigated through assessment from clinical features and by a lung injury marker (KL-6). Results: Forty-two of 103 gastric fluid specimens were positive for microbes. Ureaplasma species were detected in 23 of the 42 (55%) gastric fluid specimens. All infants with Ureaplasma species in tracheal aspirate fluid also had positive gastric fluid specimens. Compared to infants negative for gastric fluid microbes, infants positive for microbes had higher rates of maternal chorioamnionitis (18% vs 78%), premature rupture of membranes (11% vs 55%), severe bronchopulmonary dysplasia (1.6% vs 14%) and showed higher plasma KL-6 levels during the initial 4 weeks of life. Conclusion: Detection of gastric fluid microbes was correlated well with antenatal infection and severe bronchopulmonary dysplasia. Detection of Ureaplasma species in gastric fluid was associated with subsequent respiratory colonisation. These results suggest that antenatal exposure of the immature fetus to microbes may cause lung injury and promote the onset of bronchopulmonary dysplasia.

Severe Vitamin E deficiency exacerbates acute hyperoxic lung injury associated with increased oxidative stress and inflammation

Hyperoxia causes acute lung injury along with an increase of oxidative stress and inflammation. It was hypothesized that vitamin E deficiency might exacerbate acute hyperoxic lung injury. This study used α-tocopherol transfer protein knockout (α-TTP KO) mice fed a vitamin E-deficient diet (KO E(-) mice) as a model of severe vitamin E deficiency. Compared with wild-type (WT) mice, KO E(-) mice showed a significantly lower survival rate during hyperoxia. After 72 h of hyperoxia, KO E(-) mice had more severe histologic lung damage and higher values of the total cell count and the protein content of bronchoalveolar lavage fluid (BALF) than WT mice. IL-6 mRNA expression in lung tissue and the levels of 8-iso-prostaglandin F2α (8-iso-PGF2α) in both lungs and BALF were higher in KO E(-) mice than in WT mice. It was concluded that severe vitamin E deficiency exacerbates acute hyperoxic lung injury associated with increased oxidative stress or inflammation.

Plasma KL-6 Predicts the Development and Outcome of Bronchopulmonary Dysplasia

Circulating KL-6 is a specific indicator of pulmonary injury affecting the alveolar epithelium and interstitium. Our preliminary study suggested the usefulness of plasma KL-6 as a marker of bronchopulmonary dysplasia (BPD). To confirm the diagnostic value of KL-6 for BPD as well as to determine the reference range, we conducted a larger prospective study in 135 preterm infants <32 wk GA. Among the infants without oxygen dependence at a postconceptional age of 36 wk, the plasma KL-6 level showed no significant association with GA at any time. Among 42 infants <28 wk GA, plasma KL-6 levels were significantly higher in those with moderate/severe BPD compared with those with no/mild BPD. A plasma level of 199 U/mL at 1 wk or 232 U/mL at 2 wk was an excellent predictor of moderate/severe BPD <28 wk GA (positive predictive value of 83% and 80%, respectively). Unlike nonspecific markers of inflammation or fibrosis, KL-6 objectively reflects the severity of pulmonary injury irrespective of the treatment or the radiographic changes. Therefore, not only as a good marker, measurement of KL-6 may also help to provide new insights into the pathogenesis of BPD.

Antenatal exposure to Ureaplasma species exacerbates bronchopulmonary dysplasia synergistically with subsequent prolonged mechanical ventilation in preterm infants

Introduction:The presence of microorganisms in gastric fluid in neonates at birth is postulated to reflect antenatal infection and also to be associated with the development of bronchopulmonary dysplasia (BPD).Results:A logistic regression analysis, after controlling for other risk factors, indicated that Ureaplasma–positive infants were not at increased risk for moderate/severe BPD (adjusted odds ratio (OR): 2.58, 95% confidence interval (CI): 0.57–6.89, P = 0.12). However, the association between the presence of Ureaplasma species and the risk for moderate/severe BPD increased significantly in infants on mechanical ventilation (MV) ≥2 wk (adjusted OR: 4.17, 95% CI: 1.62–44.1, P = 0.009). An analysis using a lung injury marker indicated that Ureaplasma–positive infants with MV ≥2 wk, but not other infants, showed higher serum KL-6 levels in samples taken from cord blood, and that KL-6 levels increased time-dependently up to 4 wk of age.Discussion:Antenatal exposure to Ureaplasma species induces lung injury prior to birth and synergistically contributes to the development of BPD in infants requiring prolonged MV (≥2 wk).Methods:We recovered gastric fluid specimens from 122 infants with gestational age (GA) <29 wk or birth weight <1,000 g to investigate whether these microorganisms influence respiratory outcome of BPD. A PCR analysis was used to detect urease and 16S ribosomal RNA (rRNA) genes to classify neonates into Ureaplasma–positive or Ureaplasma–negative infants.

Meconium Aspiration Delays Normal Decline of Pulmonary Vascular Resistance Shortly after Birth through Lung Parenchymal Injury

Background: Persistent pulmonary hypertension of the newborn is often associated with meconium aspiration syndrome (MAS) or perinatal asphyxia. Objective: To determine the effect of meconium or asphyxia on pulmonary arterial pressure and circulating levels of vasoactive substances, we conducted a prospective study of 54 term infants, including infants with meconium-stained amniotic fluid with normal (MSAF) or abnormal (MAS) chest X-ray findings, infants with perinatal asphyxia, and controls. The purpose of this study was to determine the group most likely to have elevated pulmonary arterial pressure and a disturbed balance between vasoactive substances. Methods: To estimate the pulmonary arterial pressure by echocardiography, we used the ratio of the right to left systolic ventricular pressure (RVP/LVP ratio). We measured the plasma concentrations of endothelin-1 (ET-1), cyclic guanosine monophosphate (cGMP) as an indicator of nitric oxide (NO) production, and 6-keto-prostaglandin F1α (6-keto-PGF1α) for the estimation of prostacyclin concentration. We also measured KL-6 as a marker of lung injury. Results:The RVP/LVP ratio was significantly higher in the MAS group than the other groups on day 0. Although ET-1 and 6-keto-PGF1α levels were comparable among all groups, the cGMP level on days 3–5 and the KL-6 level throughout the first postnatal week were significantly higher in the MAS group. Conclusions: It is possible that meconium aspiration delays normal decline of pulmonary vascular resistance shortly after birth through lung parenchymal injury. The subsequent increase of cGMP in MAS may be an adaptive response to prevent further elevation of pulmonary arterial pressure by inducing NO.

Contents Vol. 99, 2011

S. Andersson, Helsinki E. Bancalari, Miami, Fla. J. Bhatia, Augusta, Ga. G. Buonocore, Siena W. Carlo, Birmingham, Ala. I. Choonara, Derby T. Curstedt, Stockholm C. Dani, Florence B. Darlow, Christchurch M. Fujimura, Osaka M. Hallman, Oulu W.W. Hay, Jr., Aurora, Colo. S.E. Juul, Seattle, Wash. M. Kaplan, Jerusalem B. Kramer, Maastricht R.J. Martin, Cleveland, Ohio C.J. Morley, Cambridge J. Neu, Gainesville, Fla. P.C. Ng, Hong Kong M.W. Obladen, Berlin A.G.S. Philip, Sebastopol, Calif. M. Post, Toronto E. Saliba, Tours O.D. Saugstad, Oslo M.S. Schimmel, Jerusalem B. Schmidt, Philadelphia, Pa. M.P. Sherman, Columbia, Mo. E.S. Shinwell, Rehovot K. Simmer, Perth, W.A. J. Smith, Tygerberg B. Sun, Shanghai N. Vain, Buenos Aires F. van Bel, Utrecht J.N. van den Anker, Washington, D.C. M. Vento Torres, Valencia M. Weindling, Liverpool J.A. Widness, Iowa City, Iowa Fetal and Neonatal Research