Evidence for pili-mediated adherence of Klebsiella pneumoniae to rat bladder epithelial cells in vitro

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Abstract
The possible role of pili in the pathogenesis of urinary tract infections caused by Klebsiella pneumoniae was studied in an in vitro mixture of a phosphate-buffered saline suspension of rat bladder epithelial cells and phosphate-buffered saline-washed K. pneumoniae. Nonpiliated and piliated populations derived from a single K. pneumoniae strain were obtained by controlling the total time of growth in broth medium. The piliated phase demonstrated a significant increase in adherence when compared to the nonpiliated phase. Incubation of the bacteria and epithelial cell mixture at 4 and 37 degrees C resulted in no differences in adherence; optimal adherence occurred at pH 5. Pretreatment of the bacteria with enzymes to destroy the pili resulted in a decrease in adherence, as did killing the bacteria by various means before adherence testing. Pretreatment of the epithelial cells with certain saccharides inhibited bacterial adherence. Finally, a 96% decrease in adherence was observed after coincubation of bacteria and epithelial cells with papain-treated antipili antibodies. Thus, it appears that pili on the surface of K. pneumoniae mediate attachment of the bacteria to rat bladder epithelial cells.