The pathogenesis of urinary tract infections associated with Escherichia coli, Staphylococcus saprophyticus and S. epidermidis

Abstract

Summary.A model was developed in mice to study the pathogenesis of urinary tract infections caused by Staphylococcus saprophyticus strains LM-1 and LM-2, Escherichia coli SP444 and S. epidermidis EOO1. Murine urinary bladders were inoculated with lo8 bacteria via a temporary urinary catheter and samples of urine and bladder were removed at days 1, 3, 5 and 10 after inoculation. They were examined both bacteriologically and by electronmicroscopy. Severe disruption of the urothelium was present immediately and the urothelium had become oedematous and ulcerated with increased urothelial exfoliation. Disruption of the urothelium was similar with all the four pathogens studied. The three strains of coagulase-negative staphylococci preferentially attached to the urothelial cell tight junctions and were not associated with polymorphonuclear leucocytes. In comparison, E. coli SP444 was randomly attached over the entire urothelium and was often in association with macrophages. Phagocytosis of E. coli by superficial urothelial cells also occurred.

Development of a PCR Assay for Identification of Staphylococci at Genus and Species Levels

“…For its part, S. epidermidis is widely recognized as an etiologic agent of bacteremia, prosthetic and natural valvular endocarditis, osteomyelitis, UTI, and peritonitis caused by ambulatory dialysis, with a frequent association with the colonization of intravascular catheters and orthopedic devices (5,32). S. saprophyticus is the second most frequently encountered organism after coliform bacilli (Escherichia coli) in acute UTI (13,28). S. saprophyticus is often isolated from sexually active young females presenting symptoms of acute UTI (33).…”

Characteristics of the Phagocytic Cup Induced by Uropathogenic Escherichia coli

“…The mice were killed 24 hr later (McTaggart et al 1990), and their urinary bladders were removed for further processing (see below). A total of eight mouse bladders were used for our experiments.…”

“…We carried out experimental UTIs using the wellestablished mouse model of UPEC invasion (McTaggart et al 1990;Mulvey et al 1998). Mouse urothelium not only expresses uroplakins that are almost identical to the human proteins (Wu et al 1994), but also, like the human urothelium, its UP Ia harbors the high mannose moiety that can serve as the receptor of UPEC adhesin FimH Xie et al 2006).…”

“…The width of this gap, estimated from the analysis of .200 phagocytic cups, is z50-150 nm. Re-examination of the thin-section images in early literature on experimental UTI showed this gap to be a common feature of the urothelial phagocytic cup (Fukushi et al 1979;McTaggart et al 1990). This gap was unlikely an artifact of the dehydration-fixation process, because it was also present in images taken by the quick-freeze/ deep-etch method (Mulvey et al 1998), which did not involve dehydration-fixation in sample preparation (Heuser 1989).…”

Dynamic interactions between host and pathogen during acute urinary tract infections

“…One arm of these induced defenses is the exfoliation of superficial bladder epithelial cells into the urine, carrying with them associated bacteria. 3,7,8 The process of exfoliation is activated in response to type 1-piliferous K12 and uropathogenic E. coli strains, but not nonpiliferous isogenic mutants, demonstrating that type 1 pili are a critical urovirulence factor involved in triggering this response. 3 However, at the present time the precise role of type 1 pili in this response is unclear.…”