Tuberculosis (TB) Facts (cont.)
Charles Patrick Davis, MD, PhD
Dr. Charles "Pat" Davis, MD, PhD, is a board certified Emergency Medicine doctor who currently practices as a consultant and staff member for hospitals. He has a PhD in Microbiology (UT at Austin), and the MD (Univ. Texas Medical Branch, Galveston). He is a Clinical Professor (retired) in the Division of Emergency Medicine, UT Health Science Center at San Antonio, and has been the Chief of Emergency Medicine at UT Medical Branch and at UTHSCSA with over 250 publications.
Jerry R. Balentine, DO, FACEP
Dr. Balentine received his undergraduate degree from McDaniel College in Westminster, Maryland. He attended medical school at the Philadelphia College of Osteopathic Medicine graduating in1983. He completed his internship at St. Joseph's Hospital in Philadelphia and his Emergency Medicine residency at Lincoln Medical and Mental Health Center in the Bronx, where he served as chief resident.
In this Article
- Tuberculosis (TB) facts
- What is tuberculosis?
- Are there different types of tuberculosis (TB)?
- What causes tuberculosis?
- What are risk factors for tuberculosis?
- What are tuberculosis symptoms and signs?
- How do physicians diagnose tuberculosis?
- What is the treatment for tuberculosis?
- What are complications of tuberculosis?
- What is the prognosis of tuberculosis?
- How can people prevent tuberculosis?
What causes tuberculosis?
The cause of TB is infection of human tissue(s) by the bacterium Mycobacterium tuberculosis (mycobacteria). These bacteria are slow growing, aerobic, and can grow within body cells (an intracellular parasitic bacterium). Its unique cell wall helps protect it from the body's defenses and gives mycobacteria the ability to retain certain dyes like fuschsin (a reddish dye) after an acid rinse that rarely happens with other bacterial, fungal, or parasitic genera.
Mycobacteria that escape destruction by body defenses may be spread by blood or lymphatic pathways to most organs, with preference to those that oxygenate well (lungs, kidneys, and bones, for example). Typical TB lesions, termed granulomas, usually consist of a central necrotic area, then a zone with macrophages, giant Langerhans cells and lymphocytes that become surrounded by immature macrophages, plasma cells, and more lymphocytes. These granulomas also contain mycobacteria. In latent infections, a fibrous capsule usually surrounds the granulomas, and in some people, the granulomas calcify, but if the immune defenses fail initially or at a later time (reactivate), the bacteria continue to spread and disrupt organ functions.
What are risk factors for tuberculosis?
There are many risk factors for developing tuberculosis. Certain groups of people have a high risk, such as people who work in hospitals and other areas where TB-infected people may reside (jails, nursing homes, group homes for HIV patients, homeless shelters). Close association with drug users, or people with known TB infections are also at higher risk. Other people at high risk include the following:
- Visitors and immigrants from areas known to have high incidence of TB
- Children and the elderly with weakened immune systems (especially those with a positive TB skin test, see below)
- Patients with HIV infection
- Drug abusers, especially IV drug abuse
- Head and neck cancer patients
- Transplant patients
- Kidney disease patients
- People undergoing immunosuppressive therapy
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