Hi,
I agree with Rina, look at the other supervisor's publications and speak to the group members, if they also don't have much of an idea about health microbiology I'd be very wary about accepting an offer.
I applied to an institute dealing with a very different kind of chemistry than what I do. My supervisor was interested in going into the field but hadn't really thought the whole thing through. In the end I became a sort of guinea pig for a project that didn't really yield anything, and any help I got from my supervisor was confusing or wrong, now I'm a few months before the end of my experimental time with very little to show for it. You need advice, regardless of where it comes from.
I would ask them, it's not rude, and often these guys get a kick out of justifying their work.
Hope it works out for you!