The Microbiology 101 version: Bacterial infections are broadly categorized into two classifications based on their cell wall, Gram Positive and Gram Negative.

The Microbiology 101 version: Bacterial infections are broadly categorized into two classifications based on their cell wall, Gram Positive and Gram Negative. Very generally, if you know what type of infection you're treating (Gram+ or Gram-), you can prescribe a class of antibiotics that works on that type of bacteria. In this broad classification, Staph and TB can be treated with similar drugs. More specifically the drug in question, Rifampin, targets a specific RNA binding site that both Staph and TB use to replicate themselves. By inhibiting this binding site, the bacteria stop reproducing and your immune system can fight off the infection.