title: Role of type 1 and S fimbriae in the pathogenesis of Escherichia coli O18:K1 bacteremia and meningitis in the infant rat.
abstract: The role of fimbriae in the pathogenesis of Escherichia coli infection was studied in the infant rat model. Rat pups were challenged intraperitoneally at the age of 5 days with E. coli K1 (strain IH3080, O18:K1:H7) and three different subpopulations (type 1, type S, or nonfimbriated) of it. All bacterial subpopulations were able to produce peritonitis, bacteremia, and meningitis. However, the type 1 fraction was the least virulent and the type S fraction was the most virulent, as judged by the bacterial counts in body fluids and by the mortality rates of the pups. Fimbrial phase variation to mainly the type-S-fimbriated forms was observed in all body fluids. An initially type-S-fimbriated inoculum remained predominantly type S fimbriated in the peritoneal fluid and blood. In the cerebrospinal fluid, however, about 50% of the bacteria were type S fimbriated and 50% were nonfimbriated 1 h after challenge with the type-S-fimbriated subpopulation; at later times the share of type-S-fimbriated bacteria also increased in the cerebrospinal fluid.
mesh_terms: D000818:Animals; D000831:Animals, Newborn / Q000382:microbiology; D004926:Escherichia coli / Q000472:pathogenicity*; D004927:Escherichia coli Infections / Q000382:microbiology*; D010861:Fimbriae, Bacterial / Q000502:physiology*; D008581:Meningitis / Q000382:microbiology*; D010538:Peritonitis / Q000382:microbiology; D018805:Sepsis / Q000382:microbiology*; D013997:Time Factors