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Teacher Answer Sheet to Debi's Story:
Explaining What Happened
1. Debi contracted tuberculosis (TB) from a student in one of her classes who had an active misdiagnosed case of TB. Debi did not know this studen
The symptoms Debi had were fatigue, weight loss, and a severe, persistent cough.
2. Treatment to cure TB is a combination of several antibiotics. Debi named standard drugs used for TB such as isoniazid and streptomycin.
3. Debi's health began improving when she started the drug therapy for TB because the bacteria that caused her tuberculosis were killed (or their growth was inhibited) by the drugs she was taking.
4. On Valentine's Day 1994, Debi learned that her tuberculosis was active again.
The drugs Debi took to cure her TB were not working because the bacteria that caused her TB had become resistant to the drugs.
5. Debi had a relapse (developed an active case of TB again), even though her health had improved and she was still taking the drugs to cure TB, because the initial treatment killed some of the
disease-causing bacteria, but hose that were resistant survived. They continued to multiply, passing their resistance on to their progeny. As a result, the disease in Debi's lungs returned. But now,
the disease-causing bacteria were all resistant to the drugs she was taking and the drugs were no longer able to cure her. Point out to students that this is an example of natural selection: the
resistance bacteria survived and passed the genes for resistance on to their progeny, whereas the susceptible bacteria did not survive. Soon all or most of the bacterial population, descendants of the resistant
organisms, was resistant.
5. Debi was finally cured of TB by taking other drugs that were still able to kill the tuberculosis bacteria and by surgical removal of the upper third of one lung that had the greatest concentration of
bacteria.
Debi's warning about TB is not to be fooled by little bacteria. In her words, they are "stubborn" and develop ways to survive. A scientist would say that bacteria rapidly evolve
resistance to the drugs we use to treat infections caused by those organisms.
ADAPTED FROM the NIH Emerging and Re-emerging Infectious Diseases(Ó 1999 by BSCS and Videodiscovery, Inc
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