Affiliation:
1. Department of Medical Microbiology and Immunology, University of Wisconsin—Madison, Madison, Wisconsin 53706
Abstract
The
Escherichia coli
hemolysin, earlier referred to as the hemolysin, is the best-characterized repeats in toxin (RTX) secreted by a type I exoprotein secretion system. The
E. coli
hemolysin is a significant virulence factor in murine models of peritonitis and ascending urinary tract infection, which suggests it is likely to be an important cytotoxin in human, extraintestinal
E. coli
diseases. Among
E. coli
or
Salmonella
strains there are no known examples of strict RTX leukotoxins in which lytic activity is limited to white blood cells. The general gene organization of the
Vibrio cholerae
RTX locus is similar to that seen with either of the
E. coli hly
and
ehx
loci with C, B, and D RTX homologs, clearly indicating it is a member of the RTX family. The hemolysin occurs less frequently in cystitis strains and only rarely among normal fecal strains. Among the extraintestinal
E. coli
isolates, the
hlyCABDgenes
were among the first virulence factors localized to unique, tRNA-associated segments of
E. coli
chromosomes. The hemolysin genes were eventually linked to P-type pilin and cytotoxic necrotizing factor-1 genes. Recent progress with its study has slowed down because of the difficulty in deriving the physical structure of the hemolysin protein or other RTX toxins and establishing its precise cytotoxic mechanism and role in pathogenesis of extraintestinal
E. coli
disease. Genomic sequencing has revealed that there are additional RTX-like genes found among many different pathogens; perhaps new efforts to discover their functions will aid progress in the RTX toxin field.
Publisher
American Society for Microbiology
Cited by
6 articles.
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