PRODUCTION OF SOLUBLE VIRULENCE FACTOR BY ESCHERICHIA-COLI

Experimental evidence suggests that adherence is a prerequisite for ba cterial infection. We demonstrated that transitional cells at the surf ace of the bladder are coated with glycosaminoglycans (proteoglycans a nd mucus) whose presence efficiently decreases bacterial adherence to the mucosa. Exposure of mucus to protamine sulfate, a quaternary amine (known to form salts with glycosaminoglycans, and inactivate them) si gnificantly increases the bacterial adherence to the bladder. Investig ators have primarily focused on bacterial surface factors (that is pil l or fimbriae, glycocalix) in relation to the ability to adhere. We ex plored the hypothesis that Escherichia coli produces a soluble virulen ce factor that increases the infection rate in rabbits by promoting ba cterial adherence to the bladder mucosa. In addition, it was proposed that this factor is a quaternary amine similar to protamine. For these studies an in vivo bacterial infection assay (which we described prev iously in rabbits) was used to examine E. coli metabolic products (sol uble virulence factor) that could promote bacterial persistence in the bladder by perturbing mucus (glycosaminoglycans), and promote bacteri al adherence and virulence. E. coli was grown in human urine and a bac terial-free supernatant was collected. Rabbit bladders were then expos ed to either this supernatant or to the same human urine that was not infected with E. coli. Results show a significantly higher bacterial p ersistence (bacterial count) in bladders pretreated with urine contain ing the E. coli supernatants compared to controls pretreated with unin fected urine (p = 0.03). The molecular weight of the putative soluble virulence factor is less than 3.5 kD. (p = 0.056) based on dialysis st udies and binds to heparin agarose affinity chromatography matrix, sug gesting that it is cationic and capable of adhering to the highly anio nic bladder mucus (glycosaminoglycans).