Restriction fragment length polymorphism and multiple copies of DNA sequences homologous with probes for P-fimbriae and hemolysin genes among uropathogenic Escherichia coli

Abstract

Hemolysin and P-fimbriae are two virulence traits frequently found together in uropathogenic Escherichia coli. Previous studies have discovered evidence both for linkage between the genes for these traits and for their duplication in the chromosomes of a limited number of strains. To test whether these observations are characteristic of uropathogenic Escherichia coli, the method of DNA hybridization to DNA restriction fragments separated by electrophoresis and transferred to nylon was used to determine copy number of genes for P-fimbriae (pap) among 51 E. coli strains isolated from symptomatic urinary tract infections. Twenty percent of the strains had more than one copy of pap homologous sequences. Fifteen strains, each representing a unique clone, were examined for the presence of sequences homologous with cloned hemolysin genes (hly). Samples of DNA from 14 of the 15 strains hybridized with hly probes. In eight strains the number of copies of pap equalled the number of copies of hly, including one strain with two apparent copies of each. Five strains appeared to have one more copy of pap than of hly, and one strain had an extra copy of hly.