Surface properties of bifidobacterial strains of human origin

Abstract

The adherence of Bifidobacterium strains isolated from infant feces and commercial fermented dairy products to enterocyte-like cells was correlated with the autoagglutination and hemagglutination properties of these organisms. These results allowed us to define two groups: (i) cell-adherent bacteria showing hemagglutination and autoagglutination and (ii) non-cell-adherent, nonhemagglutinating, nonautoagglutinating bacteria. Glass adherence was shown to be nonspecific and was discarded as a criterion for selection of adherent cells. Hydrophobicity appeared to be necessary for adhesion to enterocyte-like cells and autoagglutination. Adhesive strains were highly hydrophobic, and the degree of adherence was slightly dependent on the surface potential. Cells autoagglutinated more when the electrostatic negative charges on the cell surface were shielded by a decrease in the pH from 7 to 2. However, in some strains negative charges at the cell surface were adjuvant to adhesion, thus suggesting that specific chemical interactions occurred. The present results provide a method for preliminary selection of bacteria potentially adherent to epithelial cells by means of autoagglutination.

FIG. 1

Macroscopic and microscopic views of autoagglutinating and nonautoagglutinating Bifidobacterium cells. (A) Autoagglutinating cells gave a clear solution after the floccules precipitated. Nonagglutinating cells gave a turbid solution after more than 24 h. (B) Microscopic image of agglutinated strain CIDCA 5310 cells. Magnification, ×910. (C) Microscopic image of nonagglutinated strain CIDCA 5317 cells. Magnification, ×910.

FIG. 2

Correlation of the agglutination index (A) and glass adherence (B) with hemagglutination. For hemagglutinating (hemagg.) strains the agglutination index was 0.58 ± 0.17 (n = 27) and the percentage of adherence was 43.0 ± 21.8% (n = 33). For nonhemagglutinating (non hemagg.) strains the agglutination index was 0.37 ± 0.08 (n = 33) and the percentage of adherence was 10.4 ± 17.7% (n = 48). In all cases, significant differences were observed (P < 0.001).

FIG. 3

Agglutination index (A) and glass adherence (B) as a function of surface hydrophobicity for hemagglutinating (•) and nonhemagglutinating (○) strains. Values are the averages from at least two experiments.

FIG. 4

Correlation of agglutination index (A) and glass adherence (B) with the electrokinetic potentials of the different strains. The plots show the results for two groups of strains. Group I, strains with hydrophobic indexes greater than 80% (•) (hemagglutinating strains). Group II, strains with hydrophobic indexes less than 80% (○) (nonhemagglutinating strains).

FIG. 5

Adherence of different Bifidobacterium strains to Caco-2 cells. (A) CIDCA 531. (B) CIDCA 536. (C) CIDCA 5311.