Capsule impedes adhesion to and invasion of epithelial cells by Klebsiellapneumoniae

The adhesion of K21a, K26, K36, and K50 capsulated Klebsiella strains to il eocecal (HCT-8) and bladder (T24) epithelial cell lines was significantly l ower than that of their corresponding spontaneous noncapsulated variants K2 1a/3, K26/1, K36/3, and K50/3, respectively. Internalization of the bacteri a by both epithelial cell lines was also significantly reduced. Similarly, a capsule-switched derivative, K2(K36), that exhibited a morphologically la rger K36 capsule and formed more capsular material invaded the ileocecal ep ithelial cell line poorly compared to the corresponding K2 parent strain. N one of the capsulated strains exhibited significant mannose-sensitive type 1 fimbriae, whereas two of the noncapsulated variants K21a/3 and K50/3 exhi bited potent mannose-sensitive hemagglutinating activity. Although hemagglu tinating activity that could be attributed to mannose-resistant Klebsiella type 3 fimbriae was weak in all strains, in several cases the encapsulated parent strains exhibited lower liters than their corresponding noncapsulate d variants. Although the level of adhesion to the ileocecal cells is not di fferent from adhesion to bladder cells, bacterial internalization by bladde r cells was significantly lower than internalization by ileocecal cells, su ggesting that bladder cells lack components required for the internalizatio n of Klebsiella.