Medicine didn’t turn out this way, though. After a century of incredible discovery, most diseases have proved to be far more particular and difficult to treat. This is true even for the infections doctors once treated with penicillin: not all bacterial strains were susceptible and those that were soon developed resistance. Infections today require highly individualized treatment, sometimes with multiple therapies, based on a given strain’s pattern of anti-biotic susceptibility, the condition of the patient, and which organ systems are affected.