Why does the bacterial 'strain' matter?
When choosing a live bacteria supplement, always look out for the right strain that has been shown to be effective for your specific need (e.g. when you're on antibiotics) in human studies. If you only consider the species, it’s like choosing between a zebra and a dog - they are very different, and do very different things! The other thing to keep in mind is that more strains doesn't equate to a better product. You need to ensure each of the strains have been tested together in human studies, because just like you wouldn’t mix a chihuahua with a rottweiler without taking precautions, different strains can compete.