In that article, they are just trying to come up with answers to figure out a link to use to find a cure, it is just a small study. Here's a quote from it:
The immune system is a complex thing. Person A might get sick from something that person B doesn't have a problem with. This is always a case. The bottom line is, Leprosy is caused by a bacteria, strep is also a bacteria, and so is E-coli. Now strep and E-coli, are two bacterias that we come in contact with every day, the thing is though, most of us have an immune system that can handle the daily dose with ease. It's only when we get big doses of either, or have a compromised immune system, that we get sick from it (or a combo of both). Now... Leprosy is something that isn't all that normal, if you come around it... who knows what your immune system will do.Many of the associations, have only been found in a small series of patients, or in a single population