A fluorescence-based method for the detection of adhesive properties of lactic acid bacteria to Caco-2 cells

M.A. BIANCHI, D. DEL RIO, N. PELLEGRINI, G. SANSEBASTIANO, E. NEVIANI AND F. BRIGHENTI. 2004. Aims: The ability of probiotic micro-organisms to adhere to the intestinal surface is regarded as a substantial advantage in terms of bacteria persistence in the gastrointestinal tract. The aim of the present study was the development of a method based on fluorescent staining of bacteria and subsequent spectrofluorimetric detection to quantify the adhesion of several strains of Lactobacillus and Bifidobacterium to Caco-2 cells. Methods and Results: Lactic acid bacteria strains were subjected to fluorescent staining using the viable probe carboxyfluorescein diacetate and subsequently incubated on Caco-2 monolayers. The adhesion of the microorganisms was determined by spectrofluorimetry following the lysis of the attached bacterial cells and expressed as adhesion percentage. The values obtained for the micro-organisms tested ranged from 4% for Bifidobacterium infantis Bi1 to 10% for a Bifidobacterium mixture containing three different strains. Conclusions: In the present study we successfully applied fluorescent labelling and fluorimetric detection to investigate the adhesive properties of some Lactobacillus and Bifidobacterium strains and a Bifidobacterium mixture to Caco-2 cells. Significance and Impact of the Study: The results proved that fluorescent labelling is suitable for adhesion studies and provides a reliable and safer alternative to radioactive labelling.