Penacillin was also resisted and decried by the world's medical profession back in the 1930's as it took away the very lucrative income most GPs made "treating" and "managing" Syphilis, Gonoera, Terbeculosis, Pneumonia, etc.
Penacillin was the "Magic Bullet" to all of these and years of medical exploitation of the inflicted could be solved by a taking a course of tablets over a week or two.