Virulence factors and O groups of Escherichia coli isolates from patients with acute pyelonephritis, cystitis and asymptomatic bacteriuria

Abstract

The relationship between the presence of bacterial virulence factors and the severity of urinary tract infection (UTI) was analized in this study. The production of alpha-hemolysin (Hly), the expression of P-fimbriae and the mannose-resistant hemagglutination (MRHA) type IVa (associated with the presence of P-fimbriae), were all detected more frequently in Escherichia coli strains from acute pyelonephritis than in strains 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 between strains causing different clinical categories of UTI. Thus 88% of the E. coli strains from acute pyelonephritis showed some of the virulence factors investigated in this study, whereas only 60% (p < 0.01) and 56% (p < 0.01) repectively of the strains isolated from cystitis and asymptomatic bacteriuria possessed virulence factors. There were no significant differences in the prevalence of virulence properties between 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 strains belonging to 10 (O1, O2, O4, O6, O7, O14, O18, O22, O75 and O83) of the 12 serogroups most frequently detected in uropathogenic E. coli strains. The majority of uropathogenic O4, O6, O14, O22, O75 and O83 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 that expressed P-fimbriae. Among O2 strains we found Hly+CNF1+ strains that expressed P-fimbriae or MRHA type III and other Hly-CNF1-strains that possessed P-fimbriae. We conclude that E.coli strains isolated from pyelonephritis show virulence factors more frequently than those from cystitis and asymptomatic bacteriuria, and that strains that cause urinary tract infections in Spain belong to the same serogroups as uropathogenic E.coli isolated in other areas of the world. Our results support the special pathogenicity theory and suggest that many cases of serious urogenital disease may be caused by a limited number of P-fimbriated E.coli strains that usually produce alpha-hemolysin.

Constitutive activation of Rho proteins by CNF-1 influences tight junction structure and epithelial barrier function

“…While the role of CNF-1 as a virulence factor is controversial, it is possible that, by decreasing epithelial barrier function, the toxin facilitates access of luminal bacteria and proven virulence factors (such as hemolysin) to the sub-epithelial compartment. This could account for clinical correlations between the detection of CNF-1 and other virulence factors in diverse diseases (Andreu et al, 1997;Blanco et al, 1995;Caprioli et al, 1987;Elliott et al, 1998;Yuri et al, 1998). Furthermore, our study clearly supports a role of Rho GTPases in not only the maintenance of established TJs and paracellular permeability, but also the assembly of intercellular associations and recovery of barrier function.…”

“…Cytotoxic necrotizing factor (CNF-1), a toxin derived from necrotizing Escherichia coli, has been implicated in the pathogenesis of prostatitis (Andreu et al, 1997), urinary tract infections (Blanco et al, 1995) and others (Sears and Kaper, 1996). Its mechanism of action involves deamidation of Gln63 of Rho or Gln61 of Rac/Cdc42, resulting in constitutive activation of GTPase signaling via inhibition of GTP hydrolysis Lerm et al, 1999a;Schmidt et al, 1997).…”

Similarity and Divergence among Adherent-Invasive Escherichia coli and Extraintestinal Pathogenic E. coli Strains

“…The present study involved a collection of 86 E. coli strains, some of which were the same as those reported in previously published studies (5,7,8,17,34,39,40,42) (Table 1). Sixty-three (73.3%) were obtained from human extraintestinal infections (28 from urinary tract infections [UTIs], 21 from sepsis, 12 from meningitis, 1 from intra-abdominal pus, and 1 from a wound infection), and 23 were obtained from the intestinal mucosae of patients with CD (16 strains) or ulcerative colitis (1 strain) and the intestinal mucosae of control subjects (without inflammatory bowel disease [non-IBD]) (6 strains).…”

The p21 Rho-activating Toxin Cytotoxic Necrotizing Factor 1 Is Endocytosed by a Clathrin-independent Mechanism and Enters the Cytosol by an Acidic-dependent Membrane Translocation Step

“…Such a high affinity might be required to firmly bind toxins to the epithelial surface, because in a liquid milieu the toxin would be effectively washed from the cell surface. Because CNF1 is almost exclusively produced by uropathogenic strains of E. coli (Blanco et al 1996), this toxin might also be washed from the epithelial surface, and in this case a high receptor affinity might be necessary to compensate for the urine flow. The high affinity of CNF1 for its receptor may also be reflected in its action at very low concentration.…”

“…This toxin is most often produced by uropathogenic E. coli strains (Blanco et al, 1996). CNF1 (relative molecular mass, 113 kDa) is a single-chain toxin molecule (Falbo et al, 1993), which has been shown to induce ruffling of eukaryotic cell membranes, actin stress fiber formation, and spreading and multinucleation through the permanent activation of the small GTPase Rho (Fiorentini et al, 1995;Flatau et al, 1997;Schmidt et al, 1997).…”