My understanding is that you are advised to wear gloves when treating bumblefoot because you may have cuts on your hands or touch your face after touching the infection. Touching a bumble with unbroken skin and then washing your hands before touching anything else is not likely to give you a staph infection.
If another chicken were to mess with the bumble directly they might potentially get it from that bird, but as it is on the footpad that is unlikely. Bumblefoot could spread more easily if the infection is oozing and another hen steps on the ooze with a foot that also has an open injury. However, because they walk through their own poop and dirt all day, they will likely pick up a staph infection from their environment regardless if they have a foot wound. That's exactly how they get bumblefoot in the first place.
According to my avian vet, the best way to prevent bumblefoot is to make sure the roost isn't too high off the ground (which you've already done), and to ensure their roost perch is smooth, rounded, and not too big or too small. Rough, sharp-edged, or poorly sized roosting perches will lead to splinters or dry, cracked feet that then become prone to infection. 30-40mm in diameter is generally a good size perch for most laying hens. If you use natural wood, it is recommended to remove all bark and sand down all sides of the wood to minimize splinters or uneven knots that can cause sores.
