title: Fimbrial phase variation and systemic E. coli infection studied in the mouse peritonitis model.
abstract: Mouse peritonitis induced by intraperitoneal injection of a virulent (LD50 4 x 10(5) E. coli 018:K1:H7 strain isolated from neonatal meningitis was studied. These bacteria are capable of producing both type 1 and S fimbriae, binding to mannose or sialic acid containing glycoconjugates, respectively; the production of both fimbrial types is subject to phase variation. A broth culture of the bacteria was fractionated into subpopulations containing either type 1 or S fimbriae or neither (nonfimbriated cells), and each fraction, grown in broth to logarithmic growth phase, was used to infect groups of mice. The type 1 fraction was associated with decreased virulence as the fraction was eliminated rapidly without causing a progressive infection even at 10(6) bacteria/mouse, whereas both S and nonfimbriated cells started rapid multiplication in the peritoneal cavity and spread to the blood. In nonfibriated cells, however, S fimbriae production was induced at the same time so that at 1 h after injection, 60-70% of the bacteria in the peritoneal cavity and in the blood of the mice had S fimbriae. The injected S-fimbriated fraction remained completely S-fimbriated. Rapid induction of S fimbriae also took place in vitro when the nonfimbriated bacteria were grown in mouse serum or peritoneal fluid. Anti-S serum protected the mice from a lethal dose of S-fimbriated bacteria.
authors.affiliation: Department of General Microbiology, University of Helsinki, Finland.
authors.forename: B
authors.initials: B
authors.lastname: Nowicki
authors.forename: J
authors.initials: J
authors.lastname: Vuopio-Varkila
authors.forename: P
authors.initials: P
authors.lastname: Viljanen
authors.forename: T K
authors.initials: TK
authors.lastname: Korhonen
authors.forename: P H
authors.initials: PH
authors.lastname: Mäkelä
mesh_terms: D000818:Animals; D001422:Bacterial Adhesion; D004926:Escherichia coli / Q000472:pathogenicity; D004927:Escherichia coli Infections / Q000209:etiology*; D010861:Fimbriae, Bacterial / Q000502:physiology; D051379:Mice; D010538:Peritonitis / Q000209:etiology*; D010586:Phagocytes / Q000382:microbiology