What is difference between step a and strep b? my son tested positive for b, could he have a too?

A is a disease: Strep b does not cause disease except in newborns.

Location/issues: Group b strep is commonly found as a benign germ in the intestine or near the genitals. It can produce severe invasive disease in newborns & uti's in females. It is not a common problem for males past the newborn period. Group a strep is best known for causing throat infections but can infect many other tissues. Infection by more than one germ happens occasionally.