Bacterial adherence

The role of induced virulence factors produced by Pasteurella haemolytica in the pathogenesis of bovine pneumonic pasteurellosis: review and hypotheses

In the pathogenesis of pneumonic pasteurellosis, there is an abrupt commensal to pathogen shift from a predominance of P. haemolytica serotype 2 (ST2) to serotype 1 (ST1) in the bovine upper respiratory tract (URT) microfloral population. This occurs following periods of stress associated with development of this disease. Data are reviewed from recent publications supporting the contention that surface-expressed ST1-specific factor(s) could be critical in mediating URT adhesion and colonization. Such factors may promote an increase in the number of ST1 organisms deposited through infective droplets into the lungs, beyond that efficiently cleared by normal lung defences. The seeding of these organisms into the lungs may provide numerous foci of infection that eventually progress into characteristic pneumonic lesions seen in the disease.

Isolation and characterization of monoclonal antibodies directed against different epitopes of type-1-like fimbriae from a multifimbriated E. coli strain

Monoclonal antibodies (MAbs) were raised against purified fimbriae isolated from the uropathogenic E. coli strain WF96 (O7:K1:H6:F11rel,F10). This strain expresses at least four different types of fimbriae. 11 MAbs were selected for further characterization. They are directed against epitopes of a fimbrial type which is composed of 19.5 kDa subunits. It resembles type 1 fimbriae with regard to its high resistance to disruption by SDS. The MAbs were tested for crossreactivity to type 1 fimbriae and other fimbriae with known F-serotypes by ELISA. Two of these MAbs, Pili III 2F7 and Pili III 68C5, were directed against an epitope which was also found on MS fimbriae (type 1). Thus type 1 like fimbriae of E. coli WF96 share at least one epitope with MS fimbriae. Nevertheless, the antigenic properties of these two fimbrial types were found not to be completely identical, since all the other 9 MAbs were not crossreactive. The MAbs were not able to inhibit haemagglutination of erythrocytes of different species and thus not directed against adhesive sites of the fimbriae. All the epitopes detected by MAbs were accessible on native fimbriae; some of them were also detectable on denatured fimbrial subunits. Electron micrographs revealed that these epitopes were evenly distributed on the fimbrial organelle.

Type 1 fimbriate strains of Escherichia coli initiate renal parenchymal scarring

The renal scarring which characterizes chronic pyelonephritis is initiated by bacterial infection and is independent on the activation of an inflammatory response. Although the presence of polymorphonuclear leukocytes (PMN) is essential for initiating the scarring process, the bacterial structures responsible for their activation have not been investigated. In an animal model of chronic pyelonephritis the surface area of the renal scars produced by Type 1 fimbriate escherichia coli (E. coli) was significantly greater than that of those produced by P fimbriate and non-fimbriate strains (P less than 0.01). The activation of human PMN by the same Type 1 fimbriate organisms resulted in a significant release of lysosomal neutral protease activity (P less than 0.001) and activation of the respiratory burst (P less than 0.01). The neutral protease release in response to P fimbriate and non-fimbriate organisms was not significantly increased. The extent of renal scarring also correlated with the release of neutral protease activity (P less than 0.02) and with the degree of activation of the respiratory burst (P less than 0.05). These results demonstrate that the ability of E. coli strains to cause renal scars may be related to their capacity to express Type 1 fimbria, which may be a causative factor in the in vivo activation of the inflammatory response.

The assessment of relative surface hydrophobicity as a factor involved in the activation of human polymorphonuclear leukocytes by uropathogenic strains of Escherichia coli

The initiation of the respiratory burst and the degranulation of human polymorphonuclear leukocytes (PMN) in response to stimulation by uropathogenic strains of Escherichia coli is dependent on the expression of Type 1 fimbriae by those strains. These PMN responses correlate with an increasing tendency of the interacting E. coli strain to be retained on hydrophobic columns. The present work assessed the measurement of relative surface hydrophobicity in relation to PMN activation. Type 1 fimbriate organisms bound most readily to Octyl-Sepharose columns and were strongly agglutinated in the salt aggregation test. In contrast, the same organisms partitioned to the dextran-rich (hydrophilic) phase of aqueous two-polymer phase systems. Electron microscopic observation of the organisms eluted from the Octyl-Sepharose columns and of the organisms recovered from both phases of the aqueous two-phase systems demonstrated, however, that both Type 1 and P-fimbriate organisms were retained on the columns and partitioned into the dextran-rich phase as a consequence of their being fimbriate and failed to identify this as a major factor in the activation of PMN. In addition electron microscopy demonstrated that each P-fimbriate population had fewer organisms expressing fimbriae than did Type 1 fimbriate populations, confirming the importance of phase variation as a factor affecting the physicochemical characteristics of a bacterial population.

Variable expression of P fimbriae in Escherichia coli urinary tract infection

Fresh urinary isolates were examined by immunofluorescence with polyclonal rabbit antibodies against type 1 and P fimbriae. This procedure showed P-fimbriate Escherichia coli in 22 of 24 samples from patients with asymptomatic bacteriuria, 24 of 26 samples from patients with cystitis, and 6 of 6 samples from patients with pyelonephritis. Type 1 fimbriae were expressed by less than 40% of isolates in all three groups. There was no relation between the presence of symptoms or the site of infection and fimbrial expression, of P or type 1, by bacteria adherent to freshly isolated uroepithelial cells.

Pigment gallstones form as a composite of bacterial microcolonies and pigment solids

Although previous studies have suggested that bacteria may contribute to pigment gallstone formation, the current experiments provide evidence that bacteria have a central role in this process. The studies included scanning electron microscopy (SEM) of gallstones, measurements of bacterial adherence to gallstones in vitro, and determination of glycocalyx elaboration by biliary bacteria. Gallstones from 85 patients were studied under SEM. Twenty-five (78%) of 32 pigment stones had evidence of bacterial microcolonies throughout the interior of the stones. Bacteria were absent from the interior of all 35 cholesterol stones studied. Composite stones (stones with separate pigment and cholesterol portions) showed evidence of bacteria within the pigment portions in 14 (78%) of 18 cases. Biliary bacteria adhered to the surface of pigment gallstones in vitro in 35 (90%) of 39 cases, compared with three (8%) of 39 cholesterol stones. Glycocalyx was elaborated by bacteria isolated from nine (82%) of 11 patients with either pigment or composite gallstones. One (33%) of three bacterial species from patients with cholesterol gallstone disease produced glycocalyx. These studies indicate that most pigment gallstones obtained from patients in Western cultures form as a composite of bacteria, bacterial glycocalyx, and pigment solids. Bacteria were found in the majority of black as well as brown pigment stones. These findings serve as the basis of a new theory of pigment stone formation in which bacteria and glycocalyx are postulated to be responsible for the precipitation and subsequent agglomeration of bilirubin pigment. These results also suggest that sepsis is more common in pigment gallstone disease because the stones can serve as a sanctuary for bacteria.

Serological response to the P fimbriae of uropathogenic Escherichia coli in pyelonephritis

Uropathogenic Escherichia coli strains isolated from four patients with pyelonephritis were characterized by their O:K serotype, hemolysin production, mannose-resistant hemagglutination, and the serotype of the P fimbriae. These P fimbriae were serotyped with specific monoclonal antibodies. Serum samples from the patients were analyzed for the presence of specific antibodies to the P fimbriae. In all cases antifimbrial antibodies were found, strongly suggesting that these P fimbriae are expressed in vivo. However, the antibodies in the patient sera were not able to inhibit the mannose-resistant hemagglutination. This finding suggests that these antibodies react with the fimbrial components and not with the minor components which are responsible for adhesion.