Tuberculosis Flashcards
Describe the process of primary tuberculosis infection and dissemination including the causative organism.
Primary Infection: (usually asymptomatic but may cough, which spreads large quamtities of mycobacterium)
A mycobaterium tuberculosis/bovis/africanum is inhaled in droplets.
Host macrophages engulf the mycobaterium and carry it to hilar lymph nodes in attempt to control the infection.
Some mycobacterium disseminate around the body via the lymphatics and bloodstream.
Granulomas (tubercules) form around the disseminated organisms in an attempt to control the infection. (type IV immune response)
Outcomes:
80% of people heal spontaneously, the body fights off and clears the infection.
20% of people the granulomas are contain the infection but it is not cleared it is dormant (not infectious and causing no harm)
A small proportion of those with dormant Tb will develop active Tb infection.
Discuss the presentations of post primary infection of Tb from reactivation?
Miliary Tb
If the infection is not properly capsulated it can disseminate into the bloodstream. Severe infection; can affect virtually anywhere in the body.
Secondary Tb
Reactivation of previously dormant Tb. Usually affects the apices of the lung causing pulmonary Tb which may spread locally or distally.
Presents with: Persistent productive cough with purulent sputum. Haemoptysis SOB and pleuritic pain. Fever Night sweats Weight loss
Can also cause: lobar collapse, and pleural effusions.
Outline the common predisposing factors?
Being from or travel to an area with endemic TB
Immunocompromised (HIV)
Alcoholism
Non-Caucasian
Social deprivation/overcrowded living conditions
Outline the investigations you would do for someone you suspect may have Tb?
Bloods: FBC U/e's LFTs CRP Blood culture (ZN stain)
CXR
Other: Heaf test (tuberculin)
Describe the presentation of non pulmonary Tb?
Lympathendopathy
CNS: Tb meningitis
Pericardium: Pericarditis and pericardial effusion
Adrenals: Adrenal destruction mimicking addisons
GI: Ileocaecal obstruction or crohns like symptoms, abcess formation (psoas)
GU: Insidious renal symptoms: polyuria, nocturia and dysuria.
Skeletal: Peripheral joint pain and spine pain (potts disease)
Millary Tb will present with night sweats, pyrexia and wt loss.
Essentially it can cause any symptoms, in endemic regions or if there has been travel to endemic regions it should feature as a differential.
How are confirmed cases of TB treated?
6 months of isoniazid and rifampicin.
Supplemented in the first 2 months with pyrazinamide and ethambutol
RIPE
Rifampacin
Isoniazid
Pyrazidamine
Ethambutol
Who should receive contact tracing for Tb?
Offer Mantoux testing to diagnose Latent TB in people who are:
-either household contacts
OR
-close work or school contacts
Of all patients diagnosed with active TB
How is latent TB treated?
6 month course of isoniazid
OR
3 month course of rifampacin and isoniazid
Why is there such an issue with multi drug resistant TB?
As there is such a huge bacterial load bacterial courses are very long.
There can be issues with compliance due to this as patients start to feel better before the course is finished.
Due to this there are multi drug resistant (MDR) strains that are resistant to both Rifampicin and isoniazid.
What methods are used to try and reduce the incidence of MDR TB?
Triple/quadruple therapy.
DOT schemes (directly observed therapy) this is used in patients where it is thought compliance may be an issue such as homeless people that do not have a fixed residence)
How is MDR TB treated?
5 drugs are used for up to a period of 2 years.
During this time patients are in specialist quarantined rooms with negative air pressure to prevent spread of the infection.
Antibiotics which are trialled are:
- high-dose isoniazid, pyrazinamide, and ethambutol
- quiniolones: levofloxacin
- capreomycin, kanamycin
