Doping tests in third world countries are ridiculously easy to circumvent. It is no coincidence that some of the best marathon runners are from Eritrea or Ethiopia. All professional athletes can dope at given stages during the year.
Bolt has a good physical stature which facilitates running the speeds he does, but the advantage is not that great. It all media gibberish, the same was often said about Armstrong, talent, hard-working etc., who was never found guilty of doping during his career either.
Look at the times he and others ran, all but him have been found guilty of being doped out of their eye-balls yet couldn't even come within a 1/10th of a second of his times. Plus, at stages in his career he's been beaten by dopers, only to thrash them in the following years.
The guy was on the juice like all others.