P-fimbriae of pyelonephritogenic Escherichia coli: detection in clinical material by a rapid receptor-specific agglutination test

A slide agglutination test to detect P-fimbriated Escherichia coli was developed by attaching glycosides containing the relevant receptor structure (alpha-D-Galp-(1-4)-beta-D-Galp) to particles. A suspension of these particles agglutinates within ten seconds when mixed with P-fimbriated bacteria. The test is named the P-specific particle agglutination test (PPA test). The PPA test is more sensitive than the haemagglutination assays previously used. The exclusive specificity of the PPA test also allows the detection of P-fimbriae on strains which additionally possess other fimbriae (e.g. X-fimbriae). Using this test, the frequency of P-fimbriated E. coli in children with acute non-obstructive pyelonephritis was shown to exceed 95%. In lower urinary tract infections the frequency of P-fimbriated E. coli was approximately 20%. Moreover, children with acute pyelonephritis were also found to be heavily colonized in both the periurethral area and the intestine with the identical P-fimbriated E. coli strain.

P-fimbriae of pyelonephritogenic Escherichia coli: identification and chemical characterization of receptors

Pyelonephritogenic Escherichia coli isolates were found to be equal in their ability to adhere to uroepithelial cells and to cause agglutination specific for human erythrocytes. This adhesive capacity was not affected by D-mannose and was found to be mediated by a new class of E. coli fimbriae named P-fimbriae. Using human erythrocytes of different blood groups, we found the receptor molecules for P-fimbriae to be associated with the P blood group antigens, i. e. glycosphingolipids corresponding to the P blood group antigens P, P1 and Pk. By agglutination studies of erythrocytes with various set-ups of these antigens as well as by inhibition studies using synthetic saccharide derivatives and by coating non-agglutinable erythrocytes with a synthetic glycolipid, the minimal receptor structure was identified as the alpha-D-Galp-(1-4)-beta-D-Galp moiety of the carbohydrate portion of these glycosphingolipids. Similar experiments on isolated uroepithelial cells proved that these glycosphingolipids also constitute the receptors in the urinary tract.

P-antigen-recognizing fimbriae from human uropathogenic Escherichia coli strains

P-antigen-recognizing fimbriae (P fimbriae) from four pyelonephritogenic Escherichia coli strains and type 1 fimbriae from an E. coli strain and a Salmonella typhimurium strain were purified. The P fimbriae were morphologically similar to type 1 fimbriae. The purified P fimbriae agglutinated neuraminidase-treated human P1 and P2k erythrocytes but not p erythrocytes, which lack all P-blood group-specific glycosphingolipids. However, coating of neuraminidase-treated p erythrocytes with globoside rendered such erythrocytes agglutinable by the P fimbriae. The hemagglutinations were in all instances fully inhibited by the synthetic alpha-D-Galp-(1-4)-beta-D-Galp-1-O-Me glycoside. The binding specificity of the P fimbriae could also be demonstrated by using fimbriae coated onto latex particles and nontreated erythrocytes. It was thus concluded that the P fimbriae recognize and bind to the alpha-D-Galp-(1-4)-beta-D-Galp carbohydrate sequence occurring in the series of P-blood group antigen-specific glycosphingolipids. In contrast to both type 1 fimbriae, all four P fimbriae preparations showed multiple bands in sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Antisera were raised in rabbits against the various E. coli fimbriae. In enzyme-linked immunosorbent assays each one of the antisera to the P fimbriae reacted to titers of log 4 to 7 with both the homologous and the heterologous P fimbriae, but not with the type 1 fimbriae of E. coli. In a reciprocal fashion, the antiserum to the type 1 fimbriae of one E. coli strain reacted only with the homologous type 1 but not with any of the P fimbriae preparations.

Effects of sublethal concentrations of antimicrobial agents on the hemagglutination, adhesion, and ultrastructure of pyelonephritogenic Escherichia coli strains

The effects of trimethoprim, sulfadiazine, sulfamethoxazole, and sulfathiazole on the hemagglutination and adhesion by three Escherichia coli strains were studied. The strains were isolated from the urine of patients with acute pyelonephritis and carried P antigen-recognizing fimbriae (P fimbriae). At antimicrobial concentrations of 12.5 to 50% of the minimal inhibitory concentration, the ability of the bacteria to agglutinate human erythrocytes and to adhere to human buccal cells was markedly reduced. This reduction corresponded to a decrease in the number of P fimbriae per cell, suggesting that the antimicrobial agents decreased adhesion and hemagglutination by interfering with the formation of fimbriae. No major changes were observed in the outer membrane protein pattern of trimethoprim-treated cells, whereas freeze-fracture electron micrographs showed deorganization of both the cytoplasmic and outer membranes in bacteria opposed to sublethal concentrations of trimethoprim.

Binding specificity of piliated strains of Escherichia coli and Salmonella typhimurium to epithelial cells, saccharomyces cerevisiae cells, and erythrocytes

The binding to mammalian cells of piliated enteric bacteria and the inhibition of the binding by antibodies to purified pili were studied. The target cells were epithelial cells from human bucca and human and rat urinary tracts, erythrocytes from various species, and Saccharomyces cerevisiae cells. The strains were selected to represent the two main agglutination patterns of enteric bacteria: mannose-resistant agglutination of human and other erythrocytes and mannose-sensitive agglutination of guinea pig and other erythrocytes. Escherichia coli 3669 caused only mannose-resistant agglutination, E. coli 6013 caused only mannose-sensitive agglutination, and E. coli 3048 caused both types of agglutination simultaneously. Salmonella typhimurium SH6749 exhibited only mannose-sensitive hemagglutination and was included to allow comparison of its pili with those of E. coli strains. The range of epithelial cells to which the bacteria adhered was related to their agglutination patterns. All four strains attached to human buccal cells. Only E. coli strains 3669 and 3048, which caused mannose-resistant agglutination, adhered to human urinary tract epithelial cells, and only those strains that caused mannose-sensitive agglutination adhered to rat urinary tract epithelial cells. The binding of S. typhimurium SH6749, but not of the other strains with mannose-sensitive agglutination, was significantly inhibited by d-mannose. Globotetraosylceramide, a glycolipid present in the human urinary tract epithelium, inhibited attachment to human uroepithelial cells of the two strains with mannose-resistant hemagglutination. As tested by the enzyme-linked immunosorbent assay, cross-reactions between type 1 pili of the E. coli strains were strong, but those between S. typhimurium and E. coli mannose-sensitive pili were weak. The two pili that induced mannose-resistant hemagglutination on E. coli did not cross-react. Significant inhibition of adhesion of all four strains was obtained with the homologous anti-pilus antiserum. The binding of bacteria to mammalian cells may thus be mediated by several types of bacterial pili reacting with different receptors on mammalian cells.

Adhesion, hemagglutination, and virulence of Escherichia coli causing urinary tract infections

The capacity of 453 Escherichia coli strains to agglutinate erythrocytes and yeast cells and to attach to human urinary tract epithelial cells was tested. The strains were isolated from the urine of patients with acute pyelonephritis, acute cystitis, or asymptomatic bacteriuria and from the stools of healthy school children. Three main patterns of hemagglutination were found: (i) mannose-resistant agglutination of human erythrocytes alone or simultaneously with mannose-sensitive agglutination of guinea pig erythrocytes; (ii) only mannose-sensitive agglutination of guinea pig and other erythrocytes; and (iii) no agglutination. Strains with mannose-resistant agglutination of human erythrocytes alone or in combination with mannose-sensitive hemagglutination attached in high numbers to human urinary tract epithelial cells. Bacteria inducing only mannose-sensitive hemagglutination attached in low numbers, and non-agglutinating strains did not bind to the urinary tract epithelial cells. The bacterial surface antigen(s) mediating mannose-resistant hemagglutination of human erythrocytes and attachment to human urinary tract epithelial cells may be one factor selecting for E. coli from among the fecal flora which infect the urinary tract. The highest proportion of strains with this property was found among acute pyelonephritis isolates (77%), and the lowest proportion of strains with this property was found among normal fecal E. coli (16%).

Characterization of type 1 pili of Salmonella typhimurium LT2

Type 1 pili from Salmonella typhimurium LT2 were purified and characterized. The pilus filaments were 6 nm in diameter and over 1 microns long. Estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the molecular weight of the pilin was 21,000. The isoelectric point of the filament was 4.1. Hydrophobic amino acids comprised 40.3% of the total amino acids of the pilin, which contained more proline, serine, and lysine than reported for the type 1 pilin of Escherichia coli. Purified pili agglutinated both horse and chicken erythrocytes and yeast cells but not bovine, sheep, or human erythrocytes. Horse erythrocyte agglutination was inhibited at lower concentrations by alpha-methyl-D-mannoside than by yeast mannane and D-fructose. Agglutination was not affected by D-galactose or sucrose. Results of the present study confirm the role of type 1 pili as Salmonella hemagglutinins and show chemical differences between the type 1 pili of S. typhimurium and E. coli.

New Method for isolation of immunologically pure pili from Escherichia coli

A new technique for purification of bacterial pili was developed and applied to Escherichia coli strains isolated from the urine of patients with symptomatic urinary tract infections. After mechanical detachment from the bacterial cells, the pili were concentrated by precipitation with ammonium sulfate, dialyzed, and solubilized in buffer containing deoxycholate. The fraction containing the pili was purufied further by ultracentrifugation in a sucrose gradient and by elution through a Sepharose 4B column in 6 M urea buffer. The pilus filaments were not dissociated by concentrated urea and were eluted in the void volume of the column. The purified pili had a molecular weight of 17,000. The isoelectric point of the pili from one of the strains was 4.9, and about 43% of the amino acids were hydrophobic. Hyperimmunesera raised in rabbits against the purified pili did not contain detectable antibodies to the lipopolysaccharide O antigen or to the capsular polysaccharide K antigen of the homologous strain. The pili obtained by this purification procedure are free from other detectable bacterial surface antigens, and the purified pilus filaments are of relatively homogeneous size. This procedure enables purification of the pili also from flagellated strains.