Compare the number of organisms present in cavitary pulmonary TB and TB infection without the disease. Explain how this affects treatment.
- - Cavitary pulmonary TB: 10^7 - 10^8 organisms
- - TB infection w/o disease: <10^5
Because mutations occur in ~1/10^6 to 1/10^8 organisms, multiple drugs must be used to treat cavitary pulmonary TB in order to prevent emergence of resistant strains. TB infection w/o the disease, however, has few enough organisms that mutation is unlikely and can, therefore, be treated with a single drug.