Fig. 5

S. pneumoniae-induced empyema is characterized by persistent pleural fibrosis, rind formation and lung restriction at 14 days. Antibiotic treatment was begun 18 h after S. pneumoniae was intrapleurally administered. a Lung tissue sections from saline and S. pneumoniae-treated mice were Trichrome stained to assess collagen deposition (blue) and determine pleural thickness. 14 days S. pneumoniae-infected mice exhibited significantly increased pleural thickening compared to saline controls. Solid arrows indicate the pleural surface and the basement membrane of the thickened visceral pleura. Broken arrows indicate areas of pneumonitis underlying the thickened pleura. Collagen deposition was detected within the pleural mesothelium of S. pneumoniae infected mice. Images were collected at 20× and are representative of 30 fields/slide and 6–8 mice/group. b Lung tissue sections from saline and S. pneumoniae treated mice were stained with picrosirius to confirm tissue collagen deposition (red–orange birefringence). S. pneumoniae infected mice demonstrated increased collagen deposition at the pleural and subpleural space when compared to saline-treated mice at 14 days. Solid arrows indicate areas of collagen deposition within the mesothelium of the visceral pleura of saline and S. pneumoniae infected mice. Images were taken at 20× and are representative of 30 fields/slide and 6–8 mice/group