title: Pneumococcal meningitis is promoted by single cocci expressing pilus adhesin RrgA.
abstract: 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.
authors.forename: Federico
authors.initials: F
authors.lastname: Iovino
authors.forename: Disa L
authors.initials: DL
authors.lastname: Hammarlöf
authors.forename: Genevieve
authors.initials: G
authors.lastname: Garriss
authors.forename: Sarah
authors.initials: S
authors.lastname: Brovall
authors.forename: Priyanka
authors.initials: P
authors.lastname: Nannapaneni
authors.forename: Birgitta
authors.initials: B
authors.lastname: Henriques-Normark
mesh_terms: D018829:Adhesins, Bacterial; D000818:Animals; D001422:Bacterial Adhesion; D001812:Blood-Brain Barrier; D001921:Brain / Q000382:microbiology; D002473:Cell Wall; D004195:Disease Models, Animal; D036781:Fimbriae Proteins / Q000378:metabolism*; D010861:Fimbriae, Bacterial / Q000378:metabolism*; D008297:Male; D008586:Meningitis, Pneumococcal / Q000382:microbiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D013296:Streptococcus pneumoniae; D037521:Virulence Factors / Q000378:metabolism*
chemical_list: D018829:Adhesins, Bacterial; C579340:RrgA protein, Streptococcus pneumoniae; D037521:Virulence Factors; D036781:Fimbriae Proteins