8. Tuberculosis
The genus mycobacterium contains over 50 species withseveral human pathogens of concern.
Mycobacteria are distinguishable from other types of bacteria bythe presence of wax layers and
high molecular weight fatty acids (mycolic acids). This complex,external structure offers
protection from acids, drying and some germicides. In fact,mycobacteria are also referred to as
acid-fast bacilli because acid treatments will not result indecolorization during staining.
One of the mycobacteria species of medical interest isMycobacterium tuberculosis, the
causative agent of tuberculosis (TB). TB is a disease thataffects millions of people worldwide.
In fact, the Center for Disease Control (CDC) estimates that onethird of the total world
population is infected with TB.
M. tuberculosis normally attacks the lungs, but caninfrequently infect other areas of the body.
An infection with M. tuberculosis can result in latentTB infection or TB disease. Latent TB
infections occur when M. tuberculosis is present butnot active. People with latent TB infections
do not exhibit any symptoms, do not feel sick, and are notinfectious. If the M. tuberculosis
becomes active and multiplies, the person will develop TBdisease.
People with TB disease are infectious. TB is spread primarily byM. tuberculosis becoming
airborne in droplets of respiratory mucus when a person with TBdisease coughs, sneezes,
sings or speaks. By breathing in the airborne bacteria, the newperson is inoculated. Symptoms
of TB disease include pain in the chest, coughing up blood orsputum, or a bad cough that lasts
three weeks or longer. TB is tested for by either a TB skin test(TST) or by a TB blood test.
Direct identification of acid-fast bacilli in sputum is alsoused to detect M. tuberculosis. Current
treatments for TB include long term use (6 to 24 months) of acombination of medications.
Questions:
1. What are some of the other symptoms of TB disease notmentioned above?
2. In the U.S., Certain populations have a disproportionate rateof TB. Which populations
are these?
3. How have antibiotic resistant strains of M.tuberculosis hindered treatment?
4. Why are many health care workers required to get tested forTB?
5. A chest x-ray is used occasionally to detect lung damage inTB patients. What is the
radiologist looking for in the x-ray?
6. How are giant African rats being used to detect TB?
7. What other sites in the body can be infected by M.tuberculosis?
8. What is the primary habitat for M.tuberculosis?
