Tuberculosis Flashcards
Primary/secondary infection
TB is spread through respiratory droplets. When the bacteria enter the lungs, they find and infect macrophages. This is called primary infection. If the bacteria are kept in check by the immune system, they will likely remain latent (true for 90% of infected people).
If someone has latent TB and it becomes active, it’s referred to as reactivation, which is a type of secondary TB infection. If someone is reinfected after being cured, it is also considered secondary TB.
Granuloma
Infected macrophages prompt an immune response, which cause immune cells to surround the area, promotes inflammation and subsequently dead cells accumulate. Combined, these cells form nodules called granulomas.
Gohn focus/complex
Further diagnosis is made if the patient has a Gohn focus, which is a granuloma large enough to be seen on an X-ray. If there is a Gohn focus and a regional lymph node is enlarged, it is referred to as a Gohn complex.
Disseminated disease
The disease can also be disseminated (Spread through an organ) to organs other than the lungs, such as the liver
Miliary TB
Miliary TB is a type of disseminated disease where there are many small areas of local disease progression throughout an organ.
Reactivation
If someone has latent TB and it becomes active, it’s referred to as reactivation, which is a type of secondary TB infection.
MDR/XDR/TDR TB
TB that is resistant to more than one antibiotic is called MDR-TB (multi-drug resistant). MDR-TB is present in all countries.
If the strain is resistant to most antibiotics it is called extremely resistant (XDR-TB).
If it is resistant to all strains, as you may have guessed, it is called totally resistant (TDR-TB). Cases are rare in the US. There were only 63 cases of XDR-TB from 1993-2011, for example. However, it is increasingly common in other countries (about 480,000 cases of MDR-TB worldwide), and surveillance is weak. It is estimated that only 18% of MDR-TB cases are reported
TB symptoms
Symptoms of TB include fever, cough, bloody sputum, weakness, and chest pain.
TB treatment (don’t need to memorize drug names, but know it’s a cocktail given for months)
About 66% of patients with active TB die if untreated. Thankfully, the death rate has been dropping in recent years.
The treatment plan includes 2 initial months of chemotherapy (antibiotics), followed by varying amounts of continuing treatment. Patients may be asked to take a complex regimen of drugs including: isoniazid (an anti-metabolite), rifampin (inhibits RNA polymerase), ethambutol (EMB) (inhibits cell wall formation) and pyrazinamide (converts to an acid and accumulates, killing the cell).
Who is more susceptible to secondary TB infection
Patients are far more likely to get secondary TB if they smoke, use intravenous drugs, are malnourished, or are HIV positive. TB is the most common cause of death in AIDS patients. Almost 400,000 HIV+ people die from TB each year. However, only about half of TB patients know if they are HIV positive, and only 70% of those who are HIV+ are on ARV treatment.
TB prevention strategies
There is a vaccine for TB which is used in other countries to prevent disease in young children. However it is not frequently used in the United States. The efficacy (effectiveness in studies) of the vaccine is around 18-30%. In some countries they use the antibiotic isoniazid prophylactically, though only about 21% of countries does so.
The most effective TB prevention program by far is called Directly Observed Treatment, Short-Course, or DOTS. It is estimated to have saved millions of lives (though how many millions depends on who you ask). It was originally organized by Dr. Karel Styblo in Tanzania in the 1970’s, but later adopted by the World Bank and WHO. DOTS has 5 basic elements:
All of the components of the DOTS program
The most effective TB prevention program by far is called Directly Observed Treatment, Short-Course, or DOTS. It is estimated to have saved millions of lives (though how many millions depends on who you ask). It was originally organized by Dr. Karel Styblo in Tanzania in the 1970’s, but later adopted by the World Bank and WHO. DOTS has 5 basic elements:
Political commitment/financing
Case detection through quality-assured bacteriology
Standardized treatment, with supervision and patient support
An effective drug supply and management system
Monitoring and evaluation system, and impact measurement
Each element of the program is vitally important, however the heart of its success is the third bullet point involving supervision and patient support. As described, patients have to take a complex daily regimen of drugs that often have serious side effects. If they are in the DOTS program, a trained doctor, nurse, or health worker will ensure that they take the correct pills every single day, and provide mental and emotional support.
DOTS-Plus
There is an extension of the DOTS program that includes MDR-TB called “DOTS-Plus”
