Tuberculosis Flashcards
Rifampicin mechanism of action
Inhibits bacterial DNA dependent RNA polymerase preventing transcription of DNA into mRNA
Potent liver enzyme inducer; causes hepatitis, orange secretions, and flu-like symptoms.
Isoniazid mechanism of action
Inhibits mycolic acid synthesis
Causes peripheral neuropathy; prevent with pyridoxine (Vitamin B6), hepatitis, and agranulocytosis. Liver enzyme inhibitor.
Pyrazinamide mechanism of action
Converted by pyrazinamidase into pyrazinoic acid which inhibits fatty acid synthase (FAS) I
Causes hyperuricaemia leading to gout, arthralgia, myalgia, and hepatitis.
Ethambutol mechanism of action
Inhibits the enzyme arabinosyl transferase which polymerizes arabinose into arabinan
Causes optic neuritis; check visual acuity before and during treatment. Dose needs adjusting in patients with renal impairment.
What is latent tuberculosis?
Latent tuberculosis is a condition where patients are asymptomatic and non-infectious.
How is latent tuberculosis diagnosed?
Diagnosis is typically made through a positive tuberculin skin test or Interferon-Gamma Release Assay (IGRA) combined with a normal chest x-ray.
What are the treatment options for latent tuberculosis according to NICE?
The treatment options are:
1. 3 months of isoniazid (with pyridoxine) and rifampicin, or
2. 6 months of isoniazid (with pyridoxine).
What factors influence the choice of treatment regimen for latent tuberculosis?
The choice of regimen is based on the person’s clinical circumstances, including age and risk factors for hepatotoxicity.
Who should receive 3 months of isoniazid and rifampicin?
People younger than 35 years should receive 3 months of isoniazid (with pyridoxine) and rifampicin if hepatotoxicity is a concern.
Who should receive 6 months of isoniazid?
6 months of isoniazid (with pyridoxine) is recommended if there are concerns about interactions with rifamycins, such as in people with HIV or those who have had a transplant.
Can people with latent tuberculosis spread the disease?
No, people with latent tuberculosis cannot pass the disease on to others.
What are the risk factors for developing active tuberculosis?
Risk factors include:
- silicosis
- chronic renal failure
- HIV positive
- solid organ transplantation with immunosuppression
- intravenous drug use
- haematological malignancy
- anti-TNF treatment
- previous gastrectomy.
What is the standard therapy for treating active tuberculosis during the initial phase?
The initial phase lasts for the first 2 months and includes Rifampicin, Isoniazid, Pyrazinamide, and Ethambutol.
The 2006 NICE guidelines recommend giving Ethambutol routinely.
What is the standard therapy for treating active tuberculosis during the continuation phase?
The continuation phase lasts for the next 4 months and includes Rifampicin and Isoniazid.
What is the treatment for latent tuberculosis?
The treatment options are 3 months of Isoniazid (with pyridoxine) and Rifampicin or 6 months of Isoniazid (with pyridoxine).
How are patients with meningeal tuberculosis treated?
Patients with meningeal tuberculosis are treated for a prolonged period of at least 12 months with the addition of steroids.
What is directly observed therapy in tuberculosis management?
Directly observed therapy with a three times a week dosing regimen may be indicated for homeless people with active tuberculosis, patients likely to have poor concordance, and all prisoners with active or latent tuberculosis.
What is immune reconstitution disease?
Immune reconstitution disease occurs typically 3-6 weeks after starting treatment and often presents with enlarging lymph nodes.
What are the adverse effects of Rifampicin?
Rifampicin is a potent liver enzyme inducer and can cause hepatitis, orange secretions, and flu-like symptoms.
What are the adverse effects of Isoniazid?
Isoniazid can cause peripheral neuropathy (prevent with pyridoxine), hepatitis, and agranulocytosis.
What are the adverse effects of Pyrazinamide?
Pyrazinamide can cause hyperuricaemia leading to gout, arthralgia, myalgia, and hepatitis.
What are the adverse effects of Ethambutol?
Ethambutol can cause optic neuritis; visual acuity should be checked before and during treatment.
What is the standard therapy for treating active tuberculosis during the initial phase?
The initial phase lasts for the first 2 months and includes Rifampicin, Isoniazid, Pyrazinamide, and Ethambutol.
The 2006 NICE guidelines recommend giving Ethambutol routinely.
What is the standard therapy for treating active tuberculosis during the continuation phase?
The continuation phase lasts for the next 4 months and includes Rifampicin and Isoniazid.
What is the treatment for latent tuberculosis?
The treatment options are 3 months of Isoniazid (with pyridoxine) and Rifampicin or 6 months of Isoniazid (with pyridoxine).
How are patients with meningeal tuberculosis treated?
Patients with meningeal tuberculosis are treated for a prolonged period of at least 12 months with the addition of steroids.
What is directly observed therapy in tuberculosis management?
Directly observed therapy with a three times a week dosing regimen may be indicated for homeless people with active tuberculosis, patients likely to have poor concordance, and all prisoners with active or latent tuberculosis.
What is immune reconstitution disease?
Immune reconstitution disease occurs typically 3-6 weeks after starting treatment and often presents with enlarging lymph nodes.
What are the adverse effects of Rifampicin?
Rifampicin is a potent liver enzyme inducer and can cause hepatitis, orange secretions, and flu-like symptoms.
What are the adverse effects of Isoniazid?
Isoniazid can cause peripheral neuropathy (prevent with pyridoxine), hepatitis, and agranulocytosis.
What are the adverse effects of Pyrazinamide?
Pyrazinamide can cause hyperuricaemia leading to gout, arthralgia, myalgia, and hepatitis.
What are the adverse effects of Ethambutol?
Ethambutol can cause optic neuritis; visual acuity should be checked before and during treatment.
What is the main technique used to screen for latent tuberculosis?
The Mantoux test is the main technique used to screen for latent tuberculosis.
What is the purpose of the interferon-gamma blood test?
It is used in specific situations such as when the Mantoux test is positive or equivocal, or in individuals where a tuberculin test may be falsely negative.
How is the Mantoux test administered?
0.1 ml of 1:1,000 purified protein derivative (PPD) is injected intradermally and the result is read 2-3 days later.
What does a Mantoux test result of < 6mm indicate?
Negative - no significant hypersensitivity to tuberculin protein.
Previously unvaccinated individuals may be given the BCG.
What does a Mantoux test result of 6 - 15mm indicate?
Positive - hypersensitive to tuberculin protein.
Should not be given BCG. May be due to previous TB infection or BCG.
What does a Mantoux test result of > 15mm indicate?
Strongly positive - strongly hypersensitive to tuberculin protein.
Suggests tuberculosis infection.
What are some causes of false negative Mantoux tests?
False negative tests may be caused by miliary TB, sarcoidosis, HIV, lymphoma, or very young age (e.g. < 6 months).
What was the Heaf test and its status?
The Heaf test was previously used in the UK but has been discontinued. It involved injection of PPD equivalent to 100,000 units per ml to the skin over the flexor surface of the left forearm.
What is the classical finding of reactivated tuberculosis on a chest x-ray?
Upper lobe cavitation is the classical finding of reactivated TB.
What is required for a sputum smear test?
3 specimens are needed for the sputum smear test.
What is the sensitivity of the sputum smear test?
The sensitivity is between 50-80%, which is decreased in individuals with HIV to around 20-30%.
What is the gold standard investigation for diagnosing tuberculosis?
Sputum culture is the gold standard investigation.
How long does a sputum culture take?
A sputum culture can take 1-3 weeks if using liquid media, and longer if using solid media.
What is the advantage of nucleic acid amplification tests (NAAT)?
NAAT allows rapid diagnosis within 24-48 hours.
How does the sensitivity of NAAT compare to other tests?
NAAT is more sensitive than smear but less sensitive than culture.
What is tuberculosis (TB)?
Tuberculosis (TB) is an infection caused by Mycobacterium tuberculosis that most commonly affects the lungs.
What are the two types of tuberculosis?
The two types of tuberculosis are primary tuberculosis and secondary (post-primary) tuberculosis.
What happens in primary tuberculosis?
In primary tuberculosis, a non-immune host exposed to M. tuberculosis may develop a primary infection of the lungs, resulting in a Ghon focus.
What is a Ghon focus?
A Ghon focus is a small lung lesion composed of tubercle-laden macrophages.
What is a Ghon complex?
The Ghon complex is the combination of a Ghon focus and hilar lymph nodes.
What happens to the initial lesion in immunocompetent individuals?
In immunocompetent individuals, the initial lesion usually heals by fibrosis.
What may happen to immunocompromised individuals with primary tuberculosis?
Immunocompromised individuals may develop disseminated disease, known as miliary tuberculosis.
What triggers secondary tuberculosis?
Secondary tuberculosis can occur if the host becomes immunocompromised, leading to reactivation of the initial infection.
Where does reactivation of secondary tuberculosis generally occur?
Reactivation generally occurs in the apex of the lungs and may spread locally or to more distant sites.
What are possible causes of immunocompromise leading to secondary tuberculosis?
Possible causes include immunosuppressive drugs (including steroids), HIV, and malnutrition.
What is the most common site for secondary tuberculosis?
The lungs remain the most common site for secondary tuberculosis.
What are some areas where extra-pulmonary infection may occur?
Extra-pulmonary infection may occur in the central nervous system, vertebral bodies, cervical lymph nodes, renal, and gastrointestinal tract.
What is the most serious complication of tuberculosis?
The most serious complication of tuberculosis is tuberculous meningitis.
What is Pott’s disease?
Pott’s disease refers to tuberculosis infection of the vertebral bodies.
What is scrofuloderma?
Scrofuloderma is a form of tuberculosis infection affecting the cervical lymph nodes.
