Firstly, a word on those funny names, L casei immunitas etc.

Bacteria are named first by genus, then species, then strain, each word getting more specific. Thus, for the strain Lactobacillus casei shirota, Lactobacillus (or sometimes just L.) is the overall genus of bacterium, casei is the species and shirota the one specific strain.

Most yoghurt drinks on the market are low strain products packed full of sugar. One likely result of using such products daily is that probably those few strains alone will be promoted but no other good strains will. Added to which, the higher the sugar content, the more likely it is that “bad bugs” will also be helped to flourish.