Use of a Density Gradient Technique for Studying Adhesion of Lactobacillus Strains to Squamous Epithelial Cells

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Abstract
A new in vitro method was developed in order to characterise the adhesion pattern of three lactobacillus strains to pig squamous epithelial cells. After radioactively labelled bacteria were incubated together with the epithelial cell suspension, the non-adhering bacterial cells were removed in a density gradient. The results were compared to those obtained by two conventional methods, direct microscopic counts of bacteria adhering to epithelial cells and adhesion of radioactively labelled bacteria to tissue pieces. The evaluation indicates that the most suitable method is dependent on morphological characteristics of the bacterial strain. The gradient separation method was useful in showing that Lactobacillus murinus strain C39b, which was obtained by sequential subculturing of L. murinus (C39a), was significantly less adhesive than the parent strain. The general adhesion pattern of the strains was persistent for all methods, however, statistical differences (t-test) occurred most frequently for the three strains when the gradient method was used.