Characterization of Lactobacillus helveticus strains isolated from Bulgarian yoghurt, cheese, plants and human faecal samples by sodium dodecilsulfate polyacrylamide gel electrophoresis of cell-wall proteins, ribotyping and pulsed field gel fingerprinting

Forty-one Lactobacillus helveticus strains were isolated from Bulgarian yoghurt, cheese wheys, plants and human faecal samples. The potential of sodium dodecilsulfate polyacrylamide gel electrophoresis (SDS PAGE) of cell-wall proteins and of ribotyping to subtype the strains was tested. Both methods grouped strains with respect to their origin into four distinct clusters with satisfactory correlation. Diversity was the greatest in plant strains, followed by (in decreasing order) strains from faecal samples, cheese wheys and yoghurt. Genetic diversity of the Lb. helveticus strains was estimated by pulsed field gel electrophoresis; good distinction between strain profiles was achieved and two clusters were indicated for strains from yoghurt and cheese. Profiles obtained with strains from faecal and plant samples were clearly different from the rest, but clusters were not well differentiated.