title: In vitro expression of Streptococcus pneumoniae ply gene in human monocytes and pneumocytes.
abstract: BACKGROUND
  Streptococcus pneumoniae is one major cause of pneumonia in human and contains various virulence factors that contribute to pathogenesis of pneumococcal disease. This study investigated the role of pneumolysin, Ply, in facilitating S. pneumoniae invasion into the host blood stream.
  
  
  METHODS
  S. pneumoniae strains were isolated from clinical blood and sputum samples and confirmed by PCR. Expression of ply gene was assessed by infecting human monocytes and pneumocytes.
  
  
  RESULTS
  A total of 23 strains of S. pneumoniae isolated from blood (n = 11) and sputum (n = 12) along with S. pneumoniae ATCC49619 were used to infect human monocyte (THP-1) and Type II pneumocyte (A549) cell lines. All clinical strains of S. pneumoniae showed higher expression of ply mRNA than the American Type Culture Collection (ATCC) strain. Among the clinical strains, blood isolates showed higher expression of ply genes than sputum isolates, i.e., 2(1.5)- to 2(1.6)-folds in THP-1 and 2(0.4)- to 2(4.9)-folds in A549 cell lines.
  
  
  CONCLUSIONS
  The data from the current study demonstrated that ply gene of blood- and sputum-derived S. pneumoniae is differentially expressed in two different cell lines. Under survival pressure, ply is highly expressed in these two cell lines for blood-derived S. pneumoniae, indicating that ply gene may facilitate S. pneumoniae invasion into the host blood system.
authors.affiliation: Department of Laboratory Medicine, Taizhou Municipal Hospital, 381# Zhongshan East Road, Taizhou, 318000, China. romanticshu@aliyun.com.
authors.forename: Da-Kang
authors.initials: DK
authors.lastname: Hu
authors.affiliation: Department of Laboratory Medicine, The First Affiliated Hospital of Nanchang University, 17# Yong Wai Zheng Street, Nanchang, 330006, China. ly13767160474@sina.com.
authors.forename: Yang
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Department of Laboratory Medicine, The Second Affiliated Hospital of Wenzhou Medical University, 109# College West Road, Wenzhou, 325027, China. 89434436@qq.com.
authors.forename: Xiang-Yang
authors.initials: XY
authors.lastname: Li
authors.affiliation: Department of Laboratory Medicine, Taizhou Municipal Hospital, 381# Zhongshan East Road, Taizhou, 318000, China. 1011575993@qq.com.
authors.forename: Ying
authors.initials: Y
authors.lastname: Qu
mesh_terms: D056809:Alveolar Epithelial Cells / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics; D002460:Cell Line; D005798:Genes, Bacterial; D006801:Humans; D066298:In Vitro Techniques; D009000:Monocytes / Q000378:metabolism*; D013296:Streptococcus pneumoniae / Q000235:genetics* / Q000472:pathogenicity; D013301:Streptolysins / Q000235:genetics*; D014774:Virulence / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D013301:Streptolysins; C032290:plY protein, Streptococcus pneumoniae