Microcalorimetric evaluation of a multi-strain probiotic: Interspecies inhibition between probiotic strains

Lactobacillus plantarum, Lactobacillus rhamnosus, Lactobacillus acidophilus and Enterococcus faecium, which are the component species of a commercially available probiotic mixture (Symprove®, P1), were grown in co-culture to determine whether they would inhibit each other in vitro using an isothermal microcalorimeter (IMC). The growth profiles in the IMC were characteristic and unique to each species while the growth profile of P1 was most similar to that of L. plantarum, suggesting this is the dominant organism in mixed-culture. Bacterial growth in the cell free supernatants (CFS) of the probiotic species were also evaluated by IMC and viable counts determined. L. plantarum was found to be the most effective species at inhibiting L. rhamnosus. Conversely, L. rhamnosus was the most effective at limiting the growth of L. plantarum. Both L. plantarum and L. rhamnosus were inhibitory toward L. acidophilus and E. faecium. E. faecium was the least inhibitory towards all the other species.