In Sweden, the physician Jürgen Lehmann became intrigued by a paper indicating that exposing tuberculosis to aspirin caused M. tuberculosis to take in more oxygen; he hypothesized that a different acid compound might inhibit the bacterium’s growth by slowing its metabolism. This turned out to be true, with the compound para-aminosalicylic acid (commonly known as PAS) proving the most effective at inhibiting the bacteria’s growth.
