Final answer:
Erysipelas is most commonly caused by a bacterial infection, specifically by the bacterium Streptococcus pyogenes, and is treated with antibiotics like penicillin.
Step-by-step explanation:
The most common type or cause of Erysipelas is a bacterial infection. Erysipelas is often caused by the bacterium Streptococcus pyogenes (Group A streptococcus), which can enter the skin through a cut or abrasion. Treatment typically includes antibiotics such as penicillin, as resistance to this medication is not widespread among streptococci currently.