Equal adhesion to pneumocytes by pneumococci inducing bacteraemia and pneumonia

Streptococcus pneumoniae (S. pneumoniae) is a leading agent worldwide, which could cause community-acquired pneumonia, bacteraemia, and meningitis. However, the pathogeneses remain unclear. This study was conducted to investigate gene pneumococcal surface antigen A (psaA) expression and the adhesion differences of various S. pneumoniae strains. A total of 24 (N) S. pneumoniae strains were collected: 11 from blood (bd-SP), 12 from sputum (sd-SP) and one was ATCC49619. One millilitre of A549 pneumocytes (3.3×108/L) and 100 µl of each S. pneumoniae strain at 1.0 McFarland were mixed and incubated under 37oC and 5% CO2 for three hours. The cells were centrifuged and extracted for psaA mRNA analysis. The former experiment was redone. After culture, the adherent cells were collected and cultured on blood agar plates. The △CT values of psaA were 18.9, 29.9±2.5, 29.6±2.0 and 16.0, 17.0±3.3, 18.6±3.8 for ATCC49619, bd-SP and sd-SP before and after stimulation respectively, with the colony units of 23, 68.4±6.7 and 59.1±7.7, which showed equal adhesion between bd-SP and sd-SP. Moderate psaA expression and adhesion of S. pneumoniae might facilitate its pathogenesis, excess of which induces faster S. pneumoniae clearance.