Surgery for tuberculosis
Tuberculosis (TB) facts
- TB is an infectious disease that’s transmitted from person to person.
- Consumption: an old and once common term for wasting away of the body, particularly from pulmonary tuberculosis (TB) at certain times in the past used interchangeably with TB
- There are many different types of TB.
- A bacterium, Mycobacterium tuberculosis, causes the disease.
- There are many risk factors for TB. Clinical symptoms and signs of pulmonary TB include fever, night sweats, cough, hemoptysis (coughing up blood-stained sputum), weight loss, fatigue, and chest pain.
- TB is contagious; the incubation and contagious periods may vary.
- Physicians definitively diagnose TB by culturing mycobacteria from sputum or biopsy specimens, but health-care professionals presumptively diagnose TB by history, physical exam, skin testing, and chest X-rays.
- Treatment of TB infection is related to the type of TB infection and often requires extended treatments (months) with one or more anti-TB drugs.
- Complications of TB range from none to chronic problems and death and include lung, kidney, and liver problems that can be severe.
- The prognosis for appropriately treated TB infection is good. The prognosis declines in people who develop complications or who have had previous TB treatments.
- Prevention of TB involves both early treatment to reduce transmission and isolation of the infected person until they are no longer contagious. There is a vaccine against TB, but it is not used routinely in the U.S. because of efficacy issues and other problems.
What is tuberculosis?
Tuberculosis (TB) is a multisystemic infectious disease caused by Mycobacterium tuberculosis (or TB, TB germs), a rod-shaped bacterium. TB (TB may stand for the disease or the bacteria that cause the disease) is the most common cause of infectious disease-related mortality worldwide (about 10 million people worldwide were sick with TB in 2017, and about 1.3 million people died from TB worldwide in 2017 according to the World Health Organization [WHO] and the CDC). HIV-associated TB infections are a leading cause of death in HIV patients. TB symptoms can span such a wide range that TB is termed the “great imitator” by many who study infectious diseases because TB symptoms can mimic many other diseases. Additional terms describe TB. The terms include consumption, Pott’s disease, active, latent, pulmonary, cutaneous, and others (see the following section), and they appear in both medical and nonmedical publications. In most instances, the different terms refer to a specific type of TB with some unique symptoms or findings. The most common site (about 85%) for TB to develop is in the pulmonary tract although it may infect other parts of the body. Humans are the only known hosts for Mycobacterium tuberculosis (although it can infect animals). The bacteria may stain weakly both gram-negative and gram-positive due to its cell surface so medical professionals use acid-fast stains to visualize the cells with a microscope.
TB has likely been infecting humans for many centuries; evidence of TB infections has been found in cadavers that date back to about 8000 BC. The Greeks termed it as a wasting away disease (phthisis). For many European countries, TB caused death in about 25% of adults and was the leading cause of death in the U.S. until the early 1900s. Robert Koch discovered TB’s cause, Mycobacterium tuberculosis, in 1882. With increased understanding of TB, public health initiatives, treatment methods like isolation of patients (quarantine), and the development of drugs to treat TB, the incidence of the disease, especially in developed countries, has been markedly reduced. However, the CDC estimates one-third of the world’s population is infected with TB with about 1.8 million deaths per year. About 60% of all TB-infected people are located in India, Indonesia, China, Nigeria, Pakistan, and South Africa.
There is a vast amount of detailed information available in the medical literature on all aspects of this potentially debilitating and lethal disease. The goal of this article is to introduce the reader to TB and help them to obtain a general knowledge about TB’s cause, transmission, diagnostic tests, treatments, and prevention methods against tuberculosis infection.
Are there different types of tuberculosis (TB)?
There are many types of tuberculosis, but the main two types are termed either active or latent tuberculosis infection. Active TB is when the disease is actively producing symptoms and can be transmitted to other people; latent disease is when the person is infected with Mycobacterium tuberculosis bacteria, but the bacteria are not producing symptoms (usually due to the body’s immune system suppressing the bacterial growth and spread) and have no TB bacteria in the sputum. People with latent TB usually cannot transfer Mycobacterium tuberculosis bacteria to others unless the immune system fails; the failure causes reactivation (bacterial growth is no longer suppressed) that results in active TB so the person becomes contagious. Latent TB resembles chickenpox infection that goes dormant and may reactivate years later.
Many other types of TB exist in either the active or latent form. These types are named for the signs and for the body systems Mycobacterium tuberculosis preferentially infect, and these infection types vary from person to person. Consequently, pulmonary tuberculosis mainly infects the pulmonary system (lungs), cutaneous TB has skin symptoms, while miliary TB describes widespread small infected sites (lesions or granulomas about 1 mm-5 mm) found throughout body organs. It is not uncommon for some people to develop more than one type of active TB. More types will be listed in the symptoms and signs section below.
What causes tuberculosis?
The cause of TB is infection of human tissue(s) by the bacterium Mycobacterium tuberculosis (mycobacteria or TB). 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 fuchsin (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?
Although TB is not easily spread, it is usually spread between people who are in close contact (working together or living together).
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
- Diabetics
- Kidney disease patients
- People undergoing immunosuppressive therapy
- Silicosis