Differential binding to and biofilm formation on, HEp-2 cells by Salmonella enterica Serovar Typhimurium is dependent upon allelic variation in the fimH gene of the fim gene cluster

Type 1 fimbria-mediated adherence to HEp-2 cells by two strainsof Salmonella enterica serovar Typhimurium was found to bedifferent. Although both strains exhibited a strong mannose-sensitivehaemagglutination reaction with guinea pig erythrocytes, characteristicof the expression of type 1 fimbriae, only one of the strains adheredin large numbers to HEp-2 cells. Characterization of the fimH genes,encoding the fimbrial adhesins, indicated two allelic variants.Using fimH mutants of the two strains it was possible to demonstratethat binding to HEp-2 cells was associated with the presence ofone of the alleles regardless of the host strain. Therefore, thisdifferential binding was not a function of the type I fimbrial shaftor the presence of other types of fimbriae produced by one strainbut not the other. These observations may explain the differencesin HEp-2 binding by type 1 fimbriate strains of Salmonella previouslyreported by several groups. Also, our studies demonstrate that theFimH adhesin can influence the efficiency of biofilm formationon HEp-2 cells using once-flow-through continuous culture conditions.The formation of biofilms on eukaryotic cells using this procedure ismore likely to represent those conditions found in the intestinaltract than conditions using batch culture techniques to investigateadherence and biofilm formation. Indeed, the increased efficiencyof biofilm formation in the murine intestinal tract confirmed the roleof one of the fimH alleles in this process.