VIRULENCE FACTORS AND O-GROUPS OF ESCHERICHIA-COLI ISOLATES FROM PATIENTS WITH ACUTE PYELONEPHRITIS, CYSTITIS AND ASYMPTOMATIC BACTERIURIA

The relationship between the presence of bacterial virulence factors a nd the severity of urinary tract infection (UTI) was analized in this study. The production of alpha-hemolysin (Hly), the expression of P-fi mbriae and the mannose-resistant hemagglutination (MRHA) type IVa (ass ociated with the presence of P-fimbriae), were all detected more frequ ently in Escherichia coli strains from acute pyelonephritis than in st rains isolated from cystitis and asymptomatic bacteriuria. In contrast , the production of cytotoxic necrotizing factor type 1 (CNF1) and the expression of MRHA types III and IVb were distributed uniformly betwe en strains causing different clinical categories of UTI. Thus 88% of t he E. coli strains from acute pyelonephritis showed some of the virule nce factors investigated in this study, whereas only 60% (p < 0.01) an d 56% (p < 0.01) repectively of the strains isolated from cystitis and asymptomatic bacteriuria possessed virulence factors. There were no s ignificant differences in the prevalence of virulence properties betwe en strains isolated from patients with or without complicating factors . Only 16% (p < 0.001) of the fecal isolates from healthy individuals showed virulence factors. The virulence factors were concentrated in s trains belonging to 10 (O1, O2, O4, O6, O7, O14, O18, O22, O75 and O83 ) of the 12 serogroups most frequently detected in uropathogenic E. co li strains. The majority of uropathogenic O4, O6, O14, O22, O75 and O8 3 E. coli strains were Hly(+)CNF1(+) and expressed P-fimbriae or MRHA type III, whereas the strains of serogroup O18 were Hly(+)CNF1(-) and P-fimbriated. Among O1 and O7 strains we found Hly(-)CNF1(-) strains t hat expressed P-fimbriae. Among O2 strains we found Hly(+)CNF1(+) stra ins that expressed P-fimbriae or MRHA type III and other Hly(-)CNF1(-) strains that possessed P-fimbriae. We conclude that E. coli strains i solated from pyelonephritis show virulence factors more frequently tha n those from cystitis and asymptomatic bacteriuria, and that strains t hat cause urinary tract infections in Spain belong to the same serogro ups as uropathogenic E. coli isolated in other areas of the world. Our results support the special pathogenicity theory and suggest that man y cases of serious urogenital disease may be caused by a limited numbe r of P-fimbriated E. coli strains that usually produce alpha-hemolysin .