TB Flashcards
who identiried the infectious nature of TB?
robert Koch- Kochs postulates
what bacteria causes TB? what are its traits?
- Mycobacterium tuberculosis.
- Aerobic, gram positive, acid-fast bacilli.
- Highly unusual cell surface made up of
lipids and mycolic acid. - Intracellular - Able to survive inside
macrophages.
how is TB transmitted?
- Transmitted by aerosolised droplet from an
infected patient - Inhaled into the alveoli of a new host
what are the outcomes of being infected with TB?
– Primary Tuberculosis (first infection)
– Complete clearance
– Post-primary Tuberculosis (re-infection)
– Active Tuberculosis
– Latent Tuberculosis
how does primary TB occur?
Mostly affects lungs – Pulmonary
Tuberculosis
* Results in an area of granulomatous
inflammation– Seen as a shadow on an x-ray, in TB it is called a Ghon focus
what is the result of 90% of primary TB?
90% of people will never develop active
disease due to a competent immune
response.
what is latent TB?
the bacillus may continue to reside trapped inside the granuloma.
how do you detect latent TB?
- A skin prick test - the tuberculin
test. Is able to detect this hypersensitivity
what can trigger reactivation to latent TB?
abnormalities in cell mediated immunity
what is used to eradiacte latent TB?
- Extended antibiotic regimes used to
eradicate latent TB
what is active or post-primary active TB?
- Small percentage develop at first acquisition.
- More commonly reactivation of latent TB infection.
- May be induced if patient becomes immunocompromised
– E.g. HIV, chemotherapy, high dose corticosteroids. - Results in an aggressive immune reaction which leads to large granulomas with a “cheesy” contents called caseation.
what does active TB look like on x-ray?
- In the lungs this material is coughed up which leads to large cavitating
lesions (observed on x-ray)
what is the 2-year mortality rate of untreated active TB ?
50%
where does extrapulmonary TB cause disease?
at almost ant site in the body
what usually causes extrapulmonary TB?
Usually caused by reactivation of latent infection
what are the most common sites of extrapulmonary tb?
– Lymph nodes; pleura; gastrointestinal tract; bone and CNS
what is disseminated disease?
(Miliary tuberculosis)
– Bacilli transported in blood or lymphatic system
– May develop as a primary infection or post primary reactivation.
– Can affect many organs and may cause diagnostic delay,
particularly if the lungs are not infected.
– More often presents in children and immunocompromised
what is the clinical presentation of active TB?
– cough, weight loss, fever, night sweats, fatigue, dyspnoea, chest pain, haemoptysis.
how do you diagnose active TB?
- Respiratory
– Chest X ray
– Acid fast bacilli test and (multiple) sputum cultures.
– Rapid diagnostic nucleic acid amplification tests (NAAT) often
this is a PCR test (polymerase chain reaction) - Non respiratory
– Biopsy / needle aspiration (culture)
– Culture any surgical / radiological sample
– MRI /CT / Ultrasound as appropriate
– Chest X ray ( to confirm/exclude respiratory disease)
how do you initially manage pulmonary TB in hospital?
- In hospital management – infection control measures required
– Patient must be isolated (single room) if possible
– Personal protective equipment (PPE), staff and visitors.
– Negative pressure room if high risk of multi–drug resistant TB (MDR-TB)
how do you initially manage pulmonary TB in community?
– Advise patient the disease is highly contagious (When active)
– Avoid work / school / crowded places
– Wear face mask in public during first 2 weeks of treatment
what are the two phases of treatment of pulmonary TB?
– Intensive (Initial) phase treatment- normally lasting two months with 4 drugs
– Continuation phase- usually 4-7 months, with 2 drugs
what is the standard treatment for pulmonary TB?
– Initial - rifampicin, isoniazid (with pyridoxine), pyrazinamide and ethambutol for 2 months
– Continuation - rifampicin, isoniazid (with pyridoxine) for a further 4 months.
what is rifampicin? how does it work?
- Bactericidal, blocks RNA polymerase and therefore prevents protein formation.
- Important member of the initial phase treatment
- Kills slowly replicating bacteria throughout the whole course.
- More active than isoniazid in the anaerobic environment of the caseous lesion
