How do staph infections affect leg ulcers?

Complicates them. It makes them worse.
Loss of protection. When an ulcer develops you lose the protection of the skin, therefore you become prone to bacterial infections.

Related Questions

Does staph cause leg ulcers?

Yes, but... If skin dries/cracks, then staph or strep may infect the soft tissue as the dermal opening creates a portal of entry... Mrsa is is quite prevalent... Be careful. Read more...