Electrophysiologic monitoring of the effects of soluble virulence factors produced by Escherichia coli infection in urine.
OBJECTIVE
The presence of soluble virulence factors in urine infected by Escherichia coli has been postulated by recent studies in a rabbit bladder model. These substances may enhance bacterial adherence by damaging the glycosaminoglycan (GAG) layer that normally blocks both bacterial adherence and diffusion of solutes to the level of the epithelial membrane. We evaluated the effects of E. coli-infected urine on New Zealand white rabbit bladder mucosal permeability by measuring conductance (g) and current (I) and then calculating resistance (R) using the formula R = I divided by g.


METHODS
Forty-five rabbit bladders were prepared and mounted in Ussing chambers. The group was divided equally into three smaller cohorts (n = 15). The first cohort (NL) was exposed to uninfected sterile-filtered urine, the second cohort (PS) was a positive control exposed to uninfected sterile-filtered urine containing protamine sulfate, and the final cohort (INFX) was exposed to supernatants of E. coli-infected (more than 10(7) colony-forming units) sterile-filtered urine. The average time of exposure was 160 minutes, and the previously mentioned electrophysiologic parameters were measured and recorded.


RESULTS
The results of the PS group showed statistically significant differences in conductance, current, and resistance compared with the NL group. The decline in resistance accompanied by elevation in both current and conductance was an indirect indication that the GAG layer was functionally disturbed with a secondary increase in mucosal permeability. In a similar fashion, the INFX group also showed a statistically significant rise in conductance as well as a decline in resistance.


CONCLUSIONS
These data support the concept that E. coli-infected urine contains soluble factors that can damage the GAG layer. Although these substances appear to be less potent than quaternary or polyamines such as protamine sulfate, their mechanism of action appears similar and may enhance bacterial virulence.
Tay
H
H
Division of Urology, University of California, San Diego Medical Center, USA.
Parsons
C L
CL
Stein
P C
PC
D000818:Animals; D001685:Biological Factors / Q000502:physiology* / Q000652:urine*; D004553:Electric Conductivity; D004594:Electrophysiology; D004926:Escherichia coli / Q000472:pathogenicity*; D004927:Escherichia coli Infections / Q000652:urine*; D005260:Female; D011817:Rabbits; D012995:Solubility; D014774:Virulence
D001685:Biological Factors