Distribution of drb genes coding for Dr binding adhesins among uropathogenic and fecal Escherichia coli isolates and identification of new subtypes

Abstract

The Dr family of related adherence structures, some fimbriated and others afimbriated, bind to decay-accelerating factor molecules on human cells. Dr is associated with recurring urinary tract infection (UTI), but the distribution of Dr subtypes among uropathogenic Escherichia coli causing UTI among otherwise healthy women has yet to be described. A total of 787 UTI and fecal E. coli isolates from college women were screened for the presence of Dr sequences (drb). Fifteen percent of UTI strains were drb positive, compared to 5% of fecal strains. The adhesin (E gene) subtype of each drb- positive strain was determined by type-specific PCR followed by restriction enzyme analysis. Among 78 drb-positive strains, we found 14 (18%) afaE1, 1 (1.3%) afaE2, 1 (1.3%) afaE3, 9 (12%) draE, 9 (12%) draE-afaE3 hybrid, 1 (1.3%) daaE, 32 (41%) afaE5, 4 (5.1%) F131 E gene-like, and 7 untypeable strains. All untypeable E genes were cloned and sequenced, revealing four additional new classes of E genes, including two similar to the previously identified nonfimbrial E series. While a great range of diversity exists among the E genes, restriction fragment length polymorphism analysis demonstrated that all of these drb operons share a highly conserved gene structure. The most common subtype, afaE5, occurred three times as often among UTI than fecal strains. Over half of the drb-positive strains and 80% of those positive for afaE5 have the same virulence signature (positive for aer, kpsMT, ompT, and fim), suggesting an association of this profile with UTI pathogenesis.