Mats Lindahl

Enhanced virulence of Staphylococcus aureus from bovine mastitis induced by growth in milk whey

The virulence towards mice of Staphylococcus aureus strains from bovine mastitis was enhanced upon growth in milk whey compared to homologous organisms grown in tryptic soy broth (TSB). In the mouse mastitis model, S. aureus grown in milk whey caused more severe lesions than homologous strains grown in TSB. Staphylococcus aureus strain F1440 grown in milk whey induced 75% mortality and local necrotic reaction in subcutaneously inoculated mice, whereas the homologous strain grown in TSB caused only 5% mortality and slight skin reaction. Extracellular capsule on milk whey-grown, S. aureus could not be demonstrated. However, diffuse type colony morphology could be correlated with an increased virulence of S. aureus towards mice.

High surface hydrophobicity of hemagglutinatingVibrio cholerae and other vibrios

Surface hydrophobicity of hemagglutinatingVibrio cholerae, Vibrio parahaemolyticus, and NAG vibrios has been investigated. Most strains caused mannose-sensitive hemagglutination of monkey, guinea pig, chicken, and mannose-resistant hemagglutination of human erythrocytes with different degrees of hemagglutinating activity. Hemagglutinating strains adsorbed to a hydrophobic gel (Octyl Sepharose), whereas nonhemagglutinating strains failed to adsorb.Vibrio cholerae and other vibrios investigated seem to have pronounced surface hydrophobicity as estimated by Octyl Sepharose and they correspondingly autoaggregated into visible cell clumps in ammonium sulfate solution at low molarity (0.2–0.4 M). Nonhemagglutinating strains did not aggregate even at high (2 M) ammonium sulfate concentration. The presence of surface hemagglutinins of vibrios is growth-media-dependent. Strains, grown in four different liquid media, produced hemagglutinins and expressed pronounced surface hydrophobicity. Studies with electron microscopy revealed the presence of fimbriae on the vibrio cells. The number of fimbriae on the cells varied from strain to strain. Some strains possessed more than 300 fimbriae/cell whereas others had less than 10 fimbriae/cell. Vibrio hemagglutinins are easily detached from the cell surface by heating or sonication, and their cell surface hydrophobicity decreased simultaneously.

Adhesive proteins of haemagglutinating Staphylococcus aureus isolated from bovine mastitis.

Two proteins derived from the cell wall of Staphylococcus aureus, exhibiting apparent molecular masses of 116 kDa and 145 kDa, were found to bind to human buccal and bovine lactiferous sinus epithelial cells. By using antibodies specific for fibronectin-binding protein of S. aureus of human origin, the 116 kDa protein, but not the 145 kDa protein, was identified as a fibronectin-binding protein. The 145 kDa protein bound to bovine fat globule membranes, human buccal epithelial cells, bovine lactiferous sinus epithelial cells and sheep erythrocytes. The properties of the 145 kDa protein suggest that it is an adhesin with a possible role in the early stages of the development of bovine mastitis.

Carbohydrate receptor specificity of K99 fimbriae of enterotoxigenicEscherichia coli

K99 Fimbriae from enterotoxigenicEscherichia coli (ETEC) were found to bind specifically to sialic acid, as measured in a haemagglutination inhibition assay using the intact bacteria and human erythrocytes. The affinity forN-glycolylneuraminic acid was about twice that ofN-acetylneuraminic acid (NeuAc), and other monosaccharides were found to be at least ten-fold less effective as inhibitors. The specificity was found to depend on electrostatic interaction where the carboxyl group and its orientation plays an important role. 2-α-Benzyl-NeuAc was a better inhibitor than 2-α-methyl-NeuAc suggesting a hydrophobic patch near the binding site on the protein. Axially oriented hydroxyl groups as in 4-epi-NeuAc and 3-hydroxy-NeuAc seemed to participate in binding since these derivatives were better inhibitors thanN-acetylneuraminic acid. K99 was found to have a higher affinity for 4-O-acetyl-NeuAc and lower affinity forN-acetylneuraminic acid withO-substituents at C7-C9 as compared toN-acetylneuraminic acid. Hence, the degree ofO-acetylation of sialic acid in the mucosa of the small intestine may influence colonization and determine susceptibility to infection.

Binding of F41 and K99 fimbriae of enterotoxigenic Escherichia coli to glycoproteins from bovine and porcine colostrum

F41 and K99 fimbriae of enterotoxigenic Escherichia coli were found to bind to periodate‐sensitive oligosaccharides of glycoproteins from bovine and porcine colostrum. Only a minor component of casein fractions (κ‐casein) possessed receptors for one type of fimbriae (K99). Both whey and fat globule membranes were rich in glycoproteins with receptor structures. Porcine colostrum seemed to contain a higher quantity of receptors than bovine colostrum.

Binding of fibronectin and type II collagen to Staphylococcus aureus from bovine mastitis: reduction of binding after growth in milk whey☆

The binding of fibronectin and type II collagen to Staphylococcus aureus strains isolated from bovine mastitis was found to be 20-80% lower for organisms grown in milk whey compared to those grown in tryptic soy broth (TSB). The reduced binding was accompanied by reduced surface hydrophobicity. The observed changes, after growth in milk whey, were not due to a mere adsorption of milk whey components. The binding of fibronectin and the degree of surface hydrophobicity of milk whey-grown bacteria became similar to that of TSB-grown bacteria after periodate treatment, whereas trypsin or papain treatments had no effect.

A periodate-sensitive anti-phagocytic surface structure, induced by growth in milk whey, on Staphylococcus aureus isolated from bovine mastitis

The phagocytic and chemiluminescent activity of purified bovine neutrophils in response to two Staphylococcus aureus strains isolated from mastitic bovine milk and grown in milk whey was studied. The activity was significantly reduced compared with the response elicited by the same strains grown in tryptic soy broth (TSB). A mild periodate treatment of the milk whey-grown strains resulted in a significant increase of both chemiluminescence and phagocytosis, whereas trypsin, subtilisin or papain treatment had no effect. The decreased binding of complement factor C3 to milk-whey-grown bacteria was restored to the level of TSB-grown homologous organisms by periodate treatment. Moreover, this treatment, but not treatment with trypsin, increased the surface hydrophobicity of milk-whey-grown bacteria. The chemiluminescent activity was as high towards heat-killed as towards live bacteria. Also, incubation of heat-killed TSB-grown bacteria in milk whey did not alter the chemiluminescent response, indicating that the reduced neutrophil activity towards milk-whey-grown bacteria was not due to binding of milk components to the microorganisms. These results strongly suggest that bovine mastitis S. aureus strains grown in milk whey produce an anti-phagocytic surface structure. This structure is heat- and protease-resistant and renders the bacterial surface hydrophilic. The anti-phagocytic material is altered or, more likely, released from the bacterial surface on periodate treatment and is probably of carbohydrate nature.

Sialic Acid and N-Acetylgalactosamine Specific Bacterial Lectins of Enterotoxigenic Escherichia Coli (ETEC)

Many pathogenic and nonpathogenic bacteria have the ability to produce proteins that mediate adhesion to surfaces. These “adhesions” are usually seen in the electron microscope as filaments, protruding from the cell surface. The filaments are called fimbriae (or pili) and in general they have the ability to bind to carbohydrates and cause hemagglutination. Their ability to mediate adhesion to cells has been correlated with the pathogenicity of bacteria.

Hemagglutination of bovine erythrocytes by enterotoxigenic E. coli (ETEC) of O 6 serogroup: Evidence for glycoconjugate receptor heterogeneity

Five strains of enterotoxigenic E. coli (ETEC) producing fimbrial antigens which cause mannose-resistant haemagglutination of bovine erythrocytes (MRHA+bov) were selected among a collection of ETEC strains of the O 6 serogroup with CFA/II-like fimbrial haemagglutinins for this study. Our findings indicate that the MRHA reaction of bovine erythrocytes with these five strains reacted differently in a reproducible manner with erythrocytes from different bovine individuals. However, the complex heterogeneity of bovine erythrocyte antigens has not made it possible to relate specific blood group antigen(s) with the MRHA reaction with these different MRHA+bov ETEC strains. We conclude that bovine erythrocytes from individual animals must be tested with a battery of ETEC strains causing MRHA+bov before use in screening for CFA/II-like haemagglutinins.