Expression of type 1 fimbriae (SEF 21) of Salmonella enterica serotype Enteritidis in the early colonisation of the rat intestine

The involvement of type 1 fimbriae in colonisation of the rat gastrointesti nal tract in vivo was investigated with Salmonella enterica serotype Enteri tidis LA5 and a mutant of LA5 denoted EAV3 unable to elaborate type 1 fimbr iae (SEF 21), Rats were given a single dose of LA5 or EAV3 or a 1:1 mixture of both, LA5 was found in higher numbers in the stomach and small intestin e than EAV3 at 6 h after infection with a single strain, but not after 6 da ys, LA5 did not out-compete EAV3 when the strains were administered togethe r. Indeed, after 6 and 21 days, EAV3 was found in the distal small intestin e and large intestine in far higher numbers than LA5. These findings sugges t that SEF 21 have an important role(s) in the early stages of infection in vivo, However, SEF 21 expression may disadvantage the pathogen in the long er term as indicated by EAV3 out-competing LA5 in the gut at 21 days.