Pneumococcal meningitis is promoted by single cocci expressing pilus adhesin RrgA

• Published in: The Journal of clinical investigation 2016-08, Vol.126 (8), p.2821-2826
• Main Authors: Iovino, Federico, Hammarlöf, Disa L, Garriss, Genevieve, Brovall, Sarah, Nannapaneni, Priyanka, Henriques-Normark, Birgitta
• Format: Article
• Language: English
• Subjects: Adhesins, Bacterial; Animals; Bacteria; Bacterial Adhesion; Biomedical research; Blood-Brain Barrier; Brain - microbiology; Brain research; Brief Report; Cell division; Cell Wall; Development and progression; Disease Models, Animal; Endothelium; Experiments; Fimbriae Proteins - metabolism; Fimbriae, Bacterial - metabolism; Gene expression; Genetic aspects; Health aspects; Male; Medicin och hälsovetenskap; Meningitis; Meningitis, Pneumococcal - microbiology; Mice; Mice, Inbred C57BL; Physiological aspects; Proteins; Streptococcus infections; Streptococcus pneumoniae; Studies; Virulence (Microbiology); Virulence Factors - metabolism
• ISSN: 0021-9738; 1558-8238; 1558-8238
• DOI: 10.1172/jci84705

Streptococcus pneumoniae (pneumococcus) is the primary cause of bacterial meningitis. Pneumococcal bacteria penetrates the blood-brain barrier (BBB), but the bacterial factors that enable this process are not known. Here, we determined that expression of pneumococcal pilus-1, which includes the pilus adhesin RrgA, promotes bacterial penetration through the BBB in a mouse model. S. pneumoniae that colonized the respiratory epithelium and grew in the bloodstream were chains of variable lengths; however, the pneumococci that entered the brain were division-competent, spherical, single cocci that expressed adhesive RrgA-containing pili. The cell division protein DivIVA, which is required for an ovoid shape, was localized at the poles and septum of pneumococcal chains of ovoid, nonseparated bacteria, but was absent in spherical, single cocci. In the bloodstream, a small percentage of pneumococci appeared as piliated, RrgA-expressing, DivIVA-negative single cocci, suggesting that only a minority of S. pneumoniae are poised to cross the BBB. Together, our data indicate that small bacterial cell size, which is signified by the absence of DivIVA, and the presence of an adhesive RrgA-containing pilus-1 mediate pneumococcal passage from the bloodstream through the BBB into the brain to cause lethal meningitis.