BINDING TO AND KILLING OF HUMAN RENAL EPITHELIAL-CELLS BY HEMOLYTIC P-FIMBRIATED ESCHERICHIA-COLI

Acute pyelonephritis is a common invasive infection frequently caused by E. coli that possess P-fimbriae and secrete hemolysin. We have exam ined the role of P fimbriae and hemolysin in the killing of putative t arget cells of acute pyelonephritis, that is, human renal epithelial c ells (HRPTEC). Cultures of HRPTEC were overlaid with (1) a prototypic pyelonephritogenic E. coli (CFT073) which expresses both P fimbriae an d hemolysin; (2) its hemolysin-negative isogenic mutant (CFT073hlyD:: TnphoA); or (3) a prototypic nonpyelonephritogenic fecal E. coli (FN41 4) which is negative for both P fimbriae and hemolysin. CFT073 and CFT 073hlyD::TnphoA but not FN414 adhered to HRPTEC, as demonstrated by el ectron microscopy and direct counting. Adherence was diminished by ant isera directed against P fimbriae and by a monoclonal antibody recogni zing the epithelial receptor for P fimbriae. CFT073 was significantly more cytolethal for HRPTEC than its hemolysin-negative mutant. The bac teria-free filtrate of CFT073 was both hemolytic and cytolethal wherea s that of CFT073hyD::TnphoA was not hemolytic and was significantly le ss cytolethal. Finally, we demonstrated that CFT073 passed through mon olayers of HRPTEC at a higher rate than CFT073hlyD::TnphoA, indicating that hemolysin damages HRPTEC, facilitating passage of bacteria throu gh the epithelial barrier. With HRPTEC and a pyelonephritogenic strain of E. coli we have reproduced in vitro bacterial attachment and toxin delivery by P fimbriae and hemolysin, factors epidemiologically assoc iated with acute pyelonephritis in patients.