Epidemiology and Infection



The role of fimbriae and flagella in the colonization, invasion and persistence of Escherichia coli O78[ratio]K80 in the day-old-chick model


R. M. LA RAGIONE a1, A. R. SAYERS a1 and M. J. WOODWARD a1c1
a1 Bacteriology Department, Veterinary Laboratories Agency, Woodham Lane, New Haw, Addlestone, Surrey KT15 3NB, UK

Abstract

To understand the role of flagella and fimbriae of Escherichia coli O78[ratio]K80 in avian colibacillosis, day-old chicks were dosed orally with defined afimbriate and or aflagellate mutants and colonization, invasion and persistence compared with that of the wild-type. In an invasion model, chicks were dosed with 1 × 105 c.f.u. of a single strain and mutants defective for type 1 fimbriae, curli fimbriae or flagella colonized livers by 24 h although the numbers of bacteria present were significantly less than the wild-type. Mutants colonized between 50 and 75% of spleens whereas the wild-type colonized 100% of spleens. Additionally, the numbers of mutant bacteria in colonized spleens were significantly less than the wild-type. Surprisingly, mutants defective for the elaboration of more than one appendage were no more attenuated than single mutants. In a persistence model, chicks were dosed with 1 × 102 c.f.u. of a single strain and mutants defective for type 1 or curli or flagella or any combination thereof persisted as assessed by cloacal swabbing for 5 weeks of the experiment less well than the wild-type. In an additional persistence model, chicks were dosed with 5 × 102 c.f.u. of each of wild-type and one mutant together. All mutants were significantly less persistent than the wild-type (P < 0·001) and one mutant which lacked type 1, curli and flagella, was eliminated within 2 weeks. Analysis of the trends of elimination indicated that flagella contributed to persistence more than curli, which contributed more than type 1 fimbriae. Here was evidence for a major role in colonization, invasion and persistence played by type 1, curli and flagella.

(Accepted December 13 1999)


Correspondence:
c1 Author for correspondence.


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