The genomes of pathogenic Escherichia coli may contain several different fimbrial operons. How bacteria regulate and coordinate the choice of fimbrial expression under different circumstances remains ...largely unanswered. In this report we have investigated the role of the sfaX(II) gene associated to the Sfa(II) fimbrial determinant in the E. coli isolate IHE3034. sfaX(II) belongs to a subfamily of genes, the 17k Da genes, located near different fimbrial operons in uropathogenic and newborn meningitis E. coli (NMEC) strains. Using the NMEC isolate IHE3034 and non-pathogenic E. coli strains we found that the sfaX(II) gene had an inhibitory effect on type 1 fimbriae expression. Down-regulation of type 1 fimbriae was exerted at transcriptional level both by inhibiting expression from the fimA promoter and by reducing the frequency of OFF-to-ON switching. The effect of sfaX(II) on expression of the recombinase FimB that catalyzes OFF-to-ON switching might explain the described reduction in percentage of ON cells. Moreover, expression of the sfaX(II) gene strongly influenced motility and flagella production of the NMEC isolate IHE3034. We propose that the sfaX(II) gene, and presumably other members in the 17 kDa gene family, may play a role in the control of virulence related gene expression in pathogenic E. coli.
Persons with selective IgA deficiency carry an increased risk of coeliac disease, inflammatory bowel disease and perhaps also gastrointestinal malignancies. Inflammatory bowel disease is associated ...with an increased carriage of adherent and haemolytic Escherichia coli in the intestinal microflora. This study was designed to investigate whether IgA-deficient individuals carry E. coli with virulence-associated properties in their gut flora. The last free-lying colony of E. coli isolates obtained from rectal flora of 25 IgA-deficient and 20 age-matched control individuals was assayed by multiplex PCR for genes for the following adhesins or virulence determinants: P, type 1 and S fimbriae, Dr haemagglutinin, haemolysin, aerobactin and the capsular types K1 and K5. E. coli strains from the intestinal microflora of IgA-deficient individuals more often had the gene for S fimbriae (36% of the strains compared with 0% in control subjects, P=0.003) as well as for haemolysin (40 vs 10% of the strains, P=0.040). IgA-deficient individuals had instead lower frequencies of E. coli carrying genes for type 1 fimbriae in their microflora (68 vs 90%, P=0.14). The results suggest that IgA-deficient individuals carry an increased frequency ofE. coli with potentially inflammatogenic properties in their microflora, which may contribute to the development of gastrointestinal disorders such as inflammatory bowel diseases.
Bacterial binding to host cell surface is considered an important initial step in the pathogenesis of many infectious diseases including meningitis. Previous studies using a laboratory
Escherichia ...coli (
E. coli) strain HB101 possessing a recombinant plasmid carrying the cloned S fimbriae gene cluster have shown that S fimbriae are the major contributor to binding to bovine brain microvascular endothelial cells (BMEC) for HB101. Our present study, however, revealed that S fimbriae did not play a major role for
E. coli K1's binding to human BMEC in vitro and crossing of the blood–brain barrier in vivo. This was shown by our demonstration that
E. coli K1 strain and its S fimbriae-operon deletion mutant exhibited similar rates of binding to human BMEC and similar rates of penetration into the central nervous system in the experimental hematogenous meningitis model. Studies are needed to identify major determinants of
E. coli K1 contributing to BMEC binding and subsequent crossing of the blood–brain barrier in vivo.
Nineteen
papC-positive cytotoxic necrotizing factor 1 (CNF1)-producing
Escherichia coli isolates from pigs with septicemia or diarrhea were tested for the presence of
pap-,
sfa-, and
afa-related ...sequences encoding P/Prs, S/F1C, and Dr/AFA adhesins respectively. Production of adhesins by isolates was tested by mannose-resistant hemagglutination (MRHA), sialidase treatment of erythrocytes and particle agglutination tests. Production of P, S, and F1C fimbriae by isolates was also examined by immunofluorescence. All isolates were
pap
+ by PCR. Eighteen isolates (95%) were MRHA for ovine and human A erythrocytes and exhibited GalNac-GalNac receptor specificity associated with class III P(Prs) adhesins. Fifteen (79%) of the 19 isolates reacted with antisera specific for one or more different P fimbrial serotypes on immunofluorescence. Three of these isolates also demonstrated Gal-Gal receptor specificity associated with class I or II P fimbrial adhesins. Fifteen (79%) of the isolates were
sfa
+ by PCR. Seven of these isolates exhibited sialidase-sensitive MRHA of bovine and human O erythrocytes and reacted with serum specific for S fimbriae on immunofluorescence. Seven of the 8
sfa
+ isolates which were MRHA-negative for bovine erythrocytes reacted with serum specific for F1C fimbriae on immunofluorescence. All isolates produced type 1 fimbriae as determined by mannose-sensitive agglutination of yeast cells. None of the isolates were
afa
+ by PCR or colony hybridization. Results suggest that most
pap
+ porcine CNF1-producing
E. coli isolates express P fimbriae bearing class III (Prs) type adhesins. In addition, most of these isolates also produce S or F1C fimbriae.
ABSTRACT
Background:
Escherichia coli (E. coli) strains, expressing S‐fimbriae, belong to the most common gram‐negative pathogens that cause sepsis and meningitis in neonates. The attachment of ...S‐fimbriae to the cell surface is mediated by membrane glycoconjugates, which often carry N‐acetylneuraminic acid.
Methods:
Binding studies were performed with glycoproteins from the whey fraction of human milk to investigate whether they exert a potential inhibitory effect on bacterial adhesion. Whey glycoproteins were separated according to their molecular weight by fast protein liquid chromatography gel filtration. After sodium dodecyl sulfate‐polyacrylamide gel electrophoresis, proteins were transferred to nitrocellulose membranes and incubated with isolated S‐fimbriae from recombinant E. coli strain HB (pANN 801‐4).
Results:
S‐fimbriae recognized four whey proteins with a molecular mass of more than 200 kDa, 170 to 150 kDa, and 80 kDa. Their glycosylation pattern was investigated using the lectins Sambucus nigra, Maackia amurensis, Galanthus nivalis, and Arachis hypogaea. Thus the presence of N‐ and O‐glycans in these proteins was confirmed. The preferential binding to N‐acetylneuraminic acid containing glycoproteins was demonstrated by a complete abolishment of these reactions by incubation with acidic lactose‐derived oligosaccharides. However, the cleavage of N‐acetylneuraminic acid from glycoproteins by mild acid hydrolysis revealed a second binding site for S‐fimbriae on milk proteins of a similar molecular weight range. Terminal galactose in human milk glycoconjugates were thought to react with S‐fimbriae as well.
Conclusion:
These data further support the opinion that glycoproteins from human milk are potential receptor analogues for certain bacteria that may prevent microbial adhesion to the epithelial cell surface.
Escherichia coliadhesins are virulence factors in intestinal and extra–intestinal infections but their role in normal intestinal colonization has not been defined. We investigated the intestinal ...adherence ofE. coliwith Dr hemagglutinin S fimbriae CFA/I or CFA/II using freshly isolated ileal or colonic enterocytes and cells from the human colonic cell line HT–29.E. coliwith S–fimbrial adhesins (Sfa I or Sfa II) P or type 1 fimbriae adhered in a non–polarized manner and in similar numbers to colonic and ileal enterocytes. S fimbriae of the variety Sfa II (originating from a meningitis isolate) mediated a stronger binding than Sfa I (of uropathogenic origin). Strains expressing Dr hemagglutinin adhered preferentially to the brush borders slightly better to colonic than ileal enterocytes. Strains expressing CFA/I or II adhered to colonic and ileal enterocytes although brush border adherence was predominantly observed with ileal cells. Binding to HT–29 cells parallelled binding to colonic enterocytes for all adhesin specificities except CFA/I. The results suggest that Dr hemagglutinin P– type 1– and S–fimbrial adhesins mediate binding to both colonic and ileal enterocytes. These specificities may contribute to the establishment ofE. coliin the intestinal microflora which precedes their spread to extra–intestinal sites.
Escherichia coli S fimbriae, which bind to sialic acid residues, are a virulence factor for extraintestinal infection, but also promote binding to intestinal epithelial cells. In this study, we ...investigated whether S fimbriae would enhance intestinal colonization by E. coli or promote translocation to extraintestinal sites. A mixture of two E. coli isogenic strains both expressing type-1 fimbriae but differing in the carriage of S fimbriae (Sfim+ and Sfim−) were given perorally to germfree neonatal, infant or adult rats. The Sfim+ bound better to rat intestinal mucus and epitheial cells. However, both strains colonized equally well in both the small and large intestine and their rate of translocation to the mesenteric lymph nodes was similar. Infant rats had higher E. coli levels in the small intestine than adult rats, but their translocation rates were lower. This was at least partly due to their milk diet, since weaned infant rats had more translocating bacteria than infant rats that continued suckling their mother. The results suggest that S fimbriae, despite binding to intestinal epithelial cells and mucus, do not contribute to either colonization or translocation in the gnotobiotic rat.
BACKGROUND:Escherichia coli (E. coli) strains, expressing S-fimbriae, belong to the most common gram-negative pathogens that cause sepsis and meningitis in neonates. The attachment of S-fimbriae to ...the cell surface is mediated by membrane glycoconjugates, which often carry N-acetylneuraminic acid.
METHODS:Binding studies were performed with glycoproteins from the whey fraction of human milk to investigate whether they exert a potential inhibitory effect on bacterial adhesion. Whey glycoproteins were separated according to their molecular weight by fast protein liquid chromatography gel filtration. After sodium dodecyl sulfate-polyacrylamide gel electrophoresis, proteins were transferred to nitrocellulose membranes and incubated with isolated S-fimbriae from recombinant E. coli strain HB (pANN 801-4).
RESULTS:S-fimbriae recognized four whey proteins with a molecular mass of more than 200 kDa, 170 to 150 kDa, and 80 kDa. Their glycosylation pattern was investigated using the lectins Sambucus nigra, Maackia amurensis, Galanthus nivalis, and Arachis hypogaea. Thus the presence of N- and O-glycans in these proteins was confirmed. The preferential binding to N-acetylneuraminic acid containing glycoproteins was demonstrated by a complete abolishment of these reactions by incubation with acidic lactose-derived oligosaccharides. However, the cleavage of N-acetylneuraminic acid from glycoproteins by mild acid hydrolysis revealed a second binding site for S-fimbriae on milk proteins of a similar molecular weight range. Terminal galactose in human milk glycoconjugates were thought to react with S-fimbriae as well.
CONCLUSION:These data further support the opinion that glycoproteins from human milk are potential receptor analogues for certain bacteria that may prevent microbial adhesion to the epithelial cell surface.
Nineteen papC-positive cytotoxic necrotizing factor 1 (CNF1)-producing Escherichia coli isolates from pigs with septicemia or diarrhea were tested for the presence of pap-, sfa-, and afa-related ...sequences encoding P/Prs, S/F1C, and Dr/AFA adhesins respectively. Production of adhesins by isolates was tested by mannose-resistant hemagglutination (MRHA), sialidase treatment of erythrocytes and particle agglutination tests. Production of P, S, and F1C fimbriae by isolates was also examined by immunofluorescence. All isolates were pap+ by PCR. Eighteen isolates (95%) were MRHA for ovine and human A erythrocytes and exhibited GalNac-GalNac receptor specificity associated with class III P(Prs) adhesins. Fifteen (79%) of the 19 isolates reacted with antisera specific for one or more different P fimbrial serotypes on immunofluorescence. Three of these isolates also demonstrated Gal-Gal receptor specificity associated with class I or II P fimbrial adhesins. Fifteen (79%) of the isolates were sfa+ by PCR. Seven of these isolates exhibited sialidase-sensitive MRHA of bovine and human O erythrocytes and reacted with serum specific for S fimbriae on immunofluorescence. Seven of the 8 sfa+ isolates which were MRHA-negative for bovine erythrocytes reacted with serum specific for F1C fimbriae on immunofluorescence. All isolates produced type 1 fimbriae as determined by mannose-sensitive agglutination of yeast cells. None of the isolates were afa+ by PCR or colony hybridization. Results suggest that most pap+ porcine CNF1-producing E. coli isolates express P fimbriae bearing class III (Prs) type adhesins. In addition, most of these isolates also produce S or F1C fimbriae.
PDF
