Cisco AAA/Identity/Nac :: ACS 5.2 Add A User Into Several Groups?

We are running two ACS appliances but we cannot figure out how we can add a user into 2 differents groups.Here's the context :We have a company A which is having devices, this company uses Group A.then we have a company B which is having devices, this company uses Group B.But the admin has to manage the devices for both companies A & B.We don't want to mix devices from company A with company B.Is there a way to add the user into both groups A & B.