what bug causes impetigo
Cause. Impetigo is usually caused by staphylococcus (staph) bacteria, but it also can be caused by group A streptococcus bacteria. Skin infections are usually caused by different types (strains) of strep bacteria than those that cause strep throat.mpetigo. Impetigo is an infection of the top layers of the skin and is most common among children ages 2 to 6 years. It usually starts when bacteria get into a cut, scratch, or insect bite.