I’m an expert in neither antibiotics nor cheese, but I don’t think the white part is penicillin per se - it’s probably a strain of the penicillium mold, which makes penicillin. There’s a whole family of them, some of which make way, way more penicillin than others. I doubt the one used in making Brie is one of the few that make any large amount of penicillin, so you’d probably have to be extraordinarily sensitive to the drug to have any bad reaction to the cheese.