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Projects
Urinary tract infections (UTI), including
cystitis and pyelonephritis, are most commonly caused by
uropathogenic strains of Escherichia coli (UPEC). Recent work has
unveiled new paradigms regarding the pathogenesis of UTI. Long
thought to be a strictly extracellular pathogen, UPEC has been
shown to invade the epithelial cells lining the bladder and to
establish large collections, termed intracellular bacterial
communities (IBCs), within the superficial epithelial cells. From
there, UPEC proceeds to form a reservoir within bladder tissue
that is quiescent and invisible to host immune defenses. This
reservoir can then serve as a seed for recurrent infection, a
finding that challenges current dogma that recurrent UTI
represents re-inoculation of the urinary tract from a
gastrointestinal E. coli population. Our studies have identified
an anti-inflammatory phenotype unique to uropathogenic strains of
E. coli that may facilitate the initial steps of the IBC pathway
and support the ability of UPEC to persist in the bladder tissue
undetected by host immune mechanisms. Our current goals are to
delineate the steps of host cell inflammatory signaling that are
interrupted by UPEC, and to identify the genetic determinants of
this virulence attribute in our prototypic cystitis strain, UTI89.
UPEC and other Gram-negative pathogens have
evolved a number of systems to sense and deal with stress in the
periplasm, which may result from environmental conditions
(temperature, pH, osmolarity, etc.) or from internal conditions
(e.g., misfolded protein in the periplasmic space). A unique
periplasmic chaperone called SurA facilitates the maturation of
integral outer membrane proteins. We have recently demonstrated
that in UPEC, SurA is required for the expression of type 1 pili,
adhesive organelles that are critical for attachment to bladder
epithelial cells and establishment of cystitis. In the UTI89 surA
mutant, type 1 pili assembly is interrupted because SurA is
required for the maturation of the type 1 outer membrane usher
protein FimD. Our data further suggest additional roles for SurA
in the IBC pathway that are type 1 independent. Current projects
aim to determine the spectrum of virulence-related outer membrane
proteins acted upon by SurA, and to detail the interaction of SurA
with its substrates. Our hope is to develop compounds to inhibit
this chaperone (which is conserved across many Gram-negative
pathogens), which may prevent or treat various Gram-negative
infectious diseases.
Neutrophils arriving in the bladder in response
to chemokines interact directly with E. coli bacteria and with
IBC-containing superficial bladder epithelial cells to control
initial infection in the murine cystitis model. Despite the
arrival of neutrophils, UPEC can multiply to high titers in the
mouse bladder by 48 hours after infection. We hypothesize that
UPEC, relative to K12 E. coli, employs strategies to resist
phagocytosis, survive within phagocytes, and/or affect the
generation of reactive oxygen species within neutrophils. Current
projects aim to determine the ability of neutrophils to ingest and
kill UPEC relative to K12 E. coli and to quantify the generation
of reactive oxygen species within neutrophils exposed to these
strains. In addition, we are detailing host-pathogen crosstalk by
profiling bacterial and eukaryotic gene expression during
phagocytosis of UPEC by human neutrophils.
This project represents an innovative synergy
between our laboratory and those of Dr. Karen Wooley, polymer
chemist and McDonnell Distinguished Professor of Arts and Sciences
at Washington University, and Dr. Wiley Youngs, organometallic
chemist at the University of Akron. Bacterial adhesins are being
engineered for coupling to the surfaces of polymer nanoparticles
loaded with silver-based antimicrobials.
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SCHOOL OF MEDICINE
