Pathogenic significance of P-fimbriated Escherichia coli in urinary tract infections

The over-all aim of this study was to determine the pathogenic significance, and bacteriological and serological characteristics of P-fimbriated organisms isolated from a general population of patients with bacteriuria. A P-receptor specific particle agglutination test was used to identify P-fimbriated bacteria among 2,010 isolates from male and female patients with bacteriuria (age range infancy to 91 years). Of the 2,010 isolates 206 (10.2 per cent) were positive for P-fimbriae by the P-receptor specific particle agglutination test. Only Escherichia coli was found to be P-fimbriated, with an incidence of 21.5 per cent among 956 Escherichia coli isolates. The critical characteristic of pyelonephritic strains of Escherichia coli was P-fimbriation. In cases of nonobstructive acute pyelonephritis 100 per cent of the infecting bacteria were P-fimbriated. The data indicated clearly that the serotype, biotype, presence of type 1 fimbriae (mannose sensitive), undefined mannose-resistant adhesions, hemolysin production and motility of P-fimbriated Escherichia coli were clinically unimportant differential strain characteristics and not indicative of the virulence of P-fimbriated Escherichia coli within clinical syndromes. Isogenic P-fimbriated Escherichia coli strains were isolated from noncompromised patients in all clinical categories, that is pyelonephritis, asymptomatic bacteriuria and cystitis. A variety of bacterial strains appears to be capable of causing acute pyelonephritis in the presence of obstructive uropathic conditions, regardless of P-fimbriation. Therefore, P-fimbriation becomes a noncritical factor in compromised patients. The P-receptor specific particle agglutination test is a simple and rapid method to determine whether bacteria are P-fimbriated and may be an important screening method to identify those bacteria isolated from individuals at risk for nonobstructive acute pyelonephritis.