What is the pathogenesis of tuberculosis?
Introduction TB is an airborne disease caused by the bacterium Mycobacterium tuberculosis (M. tuberculosis) (Figure 2.1). M. tuberculosis and seven very closely related mycobacterial species (M. bovis,
Can classical microbiological techniques improve the diagnosis of tuberculosis (TB)?
The suboptimal and often delayed results from classical microbiological techniques traditionally used in the diagnosis of TBM underscore the need for a more rapid and accurate diagnostic method to facilitate early treatment.
What are the secondary lessons of tuberculosis (TB)?
The secondary lessons caused by milliaryTB can occur at almost any anatomical location but usually involve the genitouninary system, bones, joints, lymph nodes and peritoneum. **Note: Growing tubercle- although many activated macrophages can be found surrounding, the tubercles many other macrophages present remain unactivated or poorly activated.
How is tuberculosis (TB) diagnosed in chronic meningitis?
Assessment of antibody responses to antigens of Mycobacterium tuberculosis and Cysticercus cellulosae in cerebrospinal fluid of chronic meningitis patients for definitive diagnosis as TBM/NCC by passive hemagglutination and immunoblot assays. FEMS Immunol. Med. Microbiol.33:57-61.
What is the pathogenesis of clinical tuberculosis?
Infection occurs when a person inhales droplet nuclei containing tubercle bacilli that reach the alveoli of the lungs. These tubercle bacilli are ingested by alveolar macrophages; the majority of these bacilli are destroyed or inhibited.
What are the three steps in the diagnosis of tuberculosis?
There are 3 stages of TB: exposure, latent, and active disease. A TB skin test or a TB blood test can often diagnose the infection. But other testing is also often needed. Treatment exactly as recommended is needed to cure the disease and prevent its spread to other people.
What are the phases of tuberculosis patients treatment?
Regimens for treating TB disease have an intensive phase of 2 months, followed by a continuation phase of either 4 or 7 months. The continuation phase should be extended to 28 weeks for patients who have cavitation on the intensive chest film and positive sputum cultures after 2 months of treatment.
How is clinical diagnosis of tuberculosis done?
There are two kinds of tests used to detect TB bacteria in the body: the TB skin test (TST) and TB blood tests. A positive TB skin test or TB blood test only tells that a person has been infected with TB bacteria. It does not tell whether the person has latent TB infection (LTBI) or has progressed to TB disease.
What are the 4 stages of TB?
TB infection happens in 4 stages: the initial macrophage response, the growth stage, the immune control stage, and the lung cavitation stage. These four stages happen over roughly one month.
What is the gold standard for TB diagnosis?
Nucleic Acid Amplification (NAA) Test Culture remains the gold standard for laboratory confirmation of TB disease, and growing bacteria are required to perform drug-susceptibility testing and genotyping.
WHO TB treatment guidelines?
For treatment of new cases of pulmonary or extrapulmonary TB, WHO recommends a standardized regimen consisting of two phases. The initial (intensive) phase uses four drugs (rifampicin, isoniazid, pyrazinamide and ethambutol) administered for two months.
When does TB treatment start?
Treatment of latent TB infection should start after excluding the possibility of TB disease. Groups Who Should be Given High Priority for Latent TB Infection Treatment include: People with a positive TB blood test (interferon-gamma release assay or IGRA).
WHO TB treatment categories?
WHAT IS THE TREATMENT FOR TUBERCULOSIS? Tuberculosis can be cured. Directly Observed Treatment, Short- course (DOTS) is the most effective way to ensure cure. There are three categories of treatment: Categories I, II and III and each has an Intensive Phase and Continuation Phase.
What is the most diagnostic test for TB?
The TB skin test, also known as the Mantoux tuberculin skin test, is the most common way doctors diagnose tuberculosis. They'll inject a tiny amount of fluid called tuberculin just below the skin in your forearm. It contains some inactive TB protein. You should feel a small prick from the needle.
What is the duration of TB treatment?
RIPE regimens for treating TB disease have an intensive phase of 2 months, followed by a continuation phase of either 4 or 7 months (total of 6 to 9 months for treatment). This is the preferred regimen for patients with newly diagnosed pulmonary TB.
Which test is most accurate for the diagnosis of pulmonary TB?
AFB smear microscopy and culture. For pulmonary TB, sputum is the most critical sample for laboratory testing. Direct sputum smear microscopy is the most widely used method for diagnosing pulmonary TB and is available in most primary health-care laboratories at the health-center level3,12.
What is the test for TB?
Sputum tests. If your chest X-ray shows signs of tuberculosis, your doctor might take samples of your sputum — the mucus that comes up when you cough. The samples are tested for TB bacteria. Sputum samples can also be used to test for drug-resistant strains of TB.
What test is used to test for tuberculosis?
The most commonly used diagnostic tool for tuberculosis is a skin test, though blood tests are becoming more commonplace. A small amount of a substance called tuberculin is injected just ...
How long do you have to take antibiotics for tuberculosis?
For active tuberculosis, you must take antibiotics for at least six to nine months. The exact drugs and length of treatment depend on your age, overall health, possible drug resistance and where the infection is in your body.
Can a TB test be wrong?
Results can be wrong. The TB skin test isn't perfect. Sometimes, it suggests that people have TB when they don't. It can also indicate that people don't have TB when they do. You can have a false-positive result if you've been vaccinated recently with the bacille Calmette-Guerin (BCG) vaccine.
Can TB drugs cause liver damage?
Serious side effects of TB drugs aren't common but can be dangerous when they do occur. All tuberculosis medications can be toxic to your liver. When taking these medications, call your doctor immediately if you have any of the following:
What is the classification system for TB?
The current clinical classification system for TB used in the United States is based on the pathogenesis of the disease (Table 2.8). It is intended mainly as an operational framework for public health programs. This classification system provides clinicians the opportunity to track the development of TB in their patients. Health-care providers should comply with state and local laws and regulations requiring the reporting of TB disease. All persons with Class 3 (clinically active) or Class 5 (TB suspected) TB should be reported promptly to the local or state health department. A patient should not have a Class 5 classification for more than 3 months.
What is TB in the brain?
When TB occurs in the tissue surrounding the brain or spinal cord, it is called tuberculous meningitis. Tuberculous meningitis is often seen at the base of the brain on imaging studies. Symptoms include headache, decreased level of consciousness, and neck stiffness. The duration of illness before diagnosis is variable and relates in part to the presence or absence of other sites of involvement. In many cases, patients with meningitis have abnormalities on a chest radiograph consistent with old or current TB, and often have miliary TB.
How many people with TB will develop TB?
Without treatment, approximately 5% of persons who have been infected with M. tuberculosis will develop disease in the first year or 2 after infection, and another 5% will develop disease sometime later in life. Thus, without treatment, approximately 10% of persons with normal immune systems who are infected with M. tuberculosis will develop TB disease at some point in their lives.
How does TB spread?
A small number may multiply intracellularly and are released when the macrophages die. If alive, these bacilli may spread by way of lymphatic channels or through the bloodstream to more distant tissues and organs (including areas of the body in which TB disease is most likely to develop: regional lymph nodes, apex of the lung, kidneys, brain, and bone). This process of dissemination primes the immune system for a systemic response. Further details about pathogenesis of latent tuberculosis infection (LTBI) and TB disease are described in Figure 2.3.
How is M. tuberculosis transmitted?
Infectious droplet nuclei are generated when persons who have pulmonary or laryngeal TB disease cough, sneeze, shout, or sing. Depending on the environment, these tiny particles can remain suspended in the air for several hours. M. tuberculosis is transmitted through the air , not by surface contact. Transmission occurs when a person inhales droplet nuclei containing M. tuberculosis, and the droplet nuclei traverse the mouth or nasal passages, upper respiratory tract, and bronchi to reach the alveoli of the lungs (Figure 2.2).
Where does extrapulmonary TB occur?
Extrapulmonary TB disease occurs in places other than the lungs, including the larynx, the lymph nodes, the pleura, the brain, the kidneys, or the bones and joints. In HIV-infected persons, extrapulmonary TB disease is often accompanied by pulmonary TB. Persons with extrapulmonary TB disease usually are not infectious unless they have 1) pulmonary disease in addition to extrapulmonary disease; 2) extrapulmonary disease located in the oral cavity or the larynx; or 3) extrapulmonary disease that includes an open abscess or lesion in which the concentration of organisms is high, especially if drainage from the abscess or lesion is extensive, or if drainage fluid is aerosolized. Persons with TB pleural effusions may have underlying pulmonary TB that is masked on chest radiograph because the effusion fluid compresses the lung. These patients should be considered infectious until pulmonary TB disease is excluded.
Where do tuberculosis bacilli spread?
A small number of tubercle bacilli enter the bloodstream and spread throughout the body. The tubercle bacilli may reach any part of the body,including areas where TB disease is more likely to develop (such as the brain, larynx, lymph node, lung, spine, bone, or kidney).
Which mycobacterial species are capable of causing tuberculosis?
The mycobacterial species that occurs in human and belong to M. tuberculosis complex include M. tuberculosis, M. bovis, M. bovis BCG and M. africanum: all species are capable of causing tuberculosis.
What is a Mycobacterium tuberculosis complex?
The term complex is frequently used in the clinical microbiology laboratory to describe two or more species whose distinction is complicated and of little or no medical importance.
Why is mycobacterium called mycobacterium?
Resistant to decolorization by weak mineral acids because they have an unusual cell wall that contains mycolic acid acid instead of NAM and has a very thick high lipid content (60-70%).
What are the three major groups of mycobacteria?
These are: M. tuberculosis complex. Non tuberculosis mycobacteria (NTM) Lepra bacilli.
What are the complications of PTB?
Complications of PTB includes: Dry pleurisy or pleural effusion, lung collapse, acute miliary TB and occasisonally tuberculosis meningitis.
How is antibacterial resistance acquired?
Antibacterial resistance to antibiotics is acquired mostly by mutation. The main pathology in the infected tissue caused by mycobacterial infection is primarily due to responses of the host to M. tuberculosis infection rather than any virulence factor produced by it.
How do humans get TB?
Mode of transmission of TB: Humans acquire M. tuberculosis infections aerosolized dropletes. Persons with pulmonary tuberculosis (PTB) when they cough, sneeze or speak, dropletes containing bacteria are released and people nearby who get infected. A single cough can produce 3000-5000 tiny droplet nuclei.
Extrapulmonary Tuberculosis
Previous studies have shown that extrapulmonary TB is likely a marker of underlying immune compromise. Further study of the immune response of persons with previous extrapulmonary TB provides clues to the immune factors that predispose a person to progress from latent M.
Regional Prospective Observational Research for TB- Brazil
Investigations focused on understanding the pathogenesis of progression from M. tuberculosis infection to TB disease are urgently needed. Such investigations require biological specimens collected from well-characterized latent and active TB patients.