Please do use disposable gloves when treating a suspected staph infection as staph is contagious.
I am not meaning to come off as snotty or snobbish but I saw something in your post that made me gasp.
You state that your other chickens had come up to the crate when you got them home before you noticed the bumblefoot. Quarantine has already been broken. Bummer that.
All you can do now is watch for signs of illness in your existing flock. A bird can have had an illness and survived to become a carrier of the illness.
A word of caution for you and perhaps others reading this. Please inspect any bird you are purchasing before purchasing. Look for the obvious things like ... is the bird active and alert, eyes clear and bright, feather condition, lice or mites, feet in good shape, mouth condition, sneezing, shaking head a lot, nasal discharge and the such. This will help in trying to avoid issues.
Hoping for the best outcome for your birds.