Adhesion ability of Lactobacillus to vaginal epithelial cells: study by microbiological methods

Adhesion of lactobacilli to the epithelium has been described as the first step in the formation of a barrier to prevent undesirable microbial colonization; consequently, it has been defined as a characteristic of interest for selecting probiotic strains. Several methods have been described to predict the adhesion ability of Lactobacillus. Early studies were phenomenological: it was useful to determine whether a particular bacterium could hemagglutinate, or bind to coated particles. Later, studies based on the adhesion of bacteria to epithelial cells in vitro were developed. These last assays were based on the numbers of bacteria attached to epithelial cells, which were determined by counting stained microorganisms under light microscopy or by measuring the radioactivity of previously radiolabeled bacteria. Because the microscope technique, had some disadvantages, a modification was developed in our laboratory. The technique described in this chapter is a modification of the Mardh and Weströn method. The method allows the study of the adhesion ability of bacteria, even if they are aggregating or if they are high-adherent bacteria covering a large area of the epithelial cell surface. Determination of the number of adherent bacteria by counting colonies grown in a selective media avoids the time-consuming, tedious, and hazardous counting under the light microscope and the use of radioactive methods.