BECN1 and pulmonary fibrosis: The present study is aimed at exploring the influence of miRNA-30a-50p on the pulmonary fibrosis in mice with Streptococcus pneumoniae infection through the regulation of autophagy by Beclin-1 using the classical pulmonary fibrosis animal model established in mice with Streptococcus pneumoniae infection, biochemical index detection, and quantitative reverse transcription-polymerase chain reaction (qRT-PCR) and Western blotting for determining the changes in autophagy genes and proteins.