Colonisation of the chicken caecum by afimbriate and aflagellate derivatives of Salmonella enterica serotype Enteritidis

A semi-quantitative cloacal-swab method was used as an indirect measure of caecal colonisation of one-day old and five-day old chicks after oral dosin g with wild-type Salmonella enterica serovar Enteritidis PT4 and,geneticall y defined isogenic derivatives lacking the ability to elaborate flagella or fimbriae. Birds of both ages were readily and persistently colonised by al l strains although there war a decline in shedding by the older birds after about 21 days. There were no significant differences in shedding of wild-t ype or mutants in single-dose experiments. In competition experiments, in w hich five-day old birds were dosed orally with wild-type and mutants togeth er, shedding of non-motile derivatives was significantly lower than wild-ty pe, At 35 days post infection, birds were sacrificed and direct counts of m utants and wild-type from each caecum were determined. Whilst there appeare d to be poor correlation between direct counts and the indirect swab method , the overall trends shown by these methods of assessment indicated that fl agella and not fimbriae were important in caecal colonisation in these mode ls. Crown Copyright (C) 1999 Published by Elsevier Science B.V.