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Suppression of pulmonary group B streptococcal proliferation and translocation by surfactants in ventilated near-term newborn rabbits

Abstract

Background

The pathogenesis of neonatal group B Streptococcus (GBS) lung infection may be associated with surfactant dysfunction or deficiency. This study aimed to investigate the efficacy of surfactants on early postnatal GBS infection in ventilated newborn rabbit lungs.

Methods

A near-term newborn rabbit model was established by intratracheal GBS instillation immediately at birth, followed by mechanical ventilation. At postnatal 1 h, a porcine surfactant was given intratracheally at 100 or 200 mg/kg. After 6 h, animals were euthanized, and lung and blood samples were collected for bacterial counting. Lung histopathology and messenger RNA (mRNA) expression of inflammatory mediators, surfactant proteins, and growth factors in lung tissue were assessed.

Results

The surfactants significantly suppressed (by >50%) pulmonary bacterial proliferation and systemic translocation, alleviated lung inflammatory injury, and improved alveolar expansion by morphometry, in favor of high-dose surfactants. Though the survival rate and lung mechanics were not improved, the surfactants significantly suppressed mRNA expression of proinflammatory mediators, while that for surfactant proteins and growth factors was differentially expressed, compared to the control and GBS infection groups.

Conclusion

Exogenous surfactants may provide a therapeutic alternative for neonatal lung infection by suppressing pulmonary GBS proliferation and translocation into systemic circulation, alleviating inflammatory injury and regulating growth factor expression.

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Acknowledgements

We thank Dr. Yi Liu for measurement with transmission electron microscopy, Dr. Dongmei Ding and Prof. Lian Chen for measurement of lung histology and morphometry. This study was supported by a grant from the National Natural Science Foundation (No. 81501288 to Y.D.).

Author information

Y.X. performed experiments, analyzed data, and drafted manuscript; Y.D. conceptualized and supervised the whole study plan and experiment protocol, reviewed, and modified manuscript; X.G. was responsible for measurement of lung mechanics and lung tissue processing. B.S. conceptualized the study plan, designed the experiment, interpreted the data, edited, and finalized the manuscript.

Competing interests

The authors declare no competing interests.

Correspondence to Bo Sun.

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