Tuberculosis

Write about Tuberculosis here.


Worldwide: 2 billion - 3 million/yr death rate (with HIV-related TB, leading infective cause of death)

UK: 7000/yr

10% drug-resistant


Primary TB

• Most asymptomatic, healing in 4-8/52

• Bronchial spread -> progressive consolidation and cavitation of lung parenchyma -> pleural effusions may develop

• Lymphatic spread -> progressive lymph node enlargement -> (kids) compress bronchi with obstruction, distal consolidation and development of collapse and bronchiectasis

Bronchiectasis of the middle lobe is a very typical outcome of hilar node involvement in childhood

• Haematogenous spread -> early generalisation of disease which may cause miliary tuberculosis and the lethal complication:

• Tuberculous meningitis (particularly young children)

• Infection spread during this initial illness may lie dormant in any organ of the body (e.g. bone, kidneys) for many years, only to reactivate many years later


Post-Primary TB

Pattern of disease seen after the development of specific immunity

• May occur following:

• direct progression of the initial infection or 

• result from endogenous reactivation of infection or 

• from exogenous re-infection

in a patient who has had previous contact with the organism and has developed a degree of specific immunity

Reactivation particularly occurs in old age and immuno-incompetence

• Lungs most usual site of post-primary disease

• Apices of the lungs are the commonest pulmonary site


Diagnosis

CXR

• Clinical

• Sputum - Acid & Alcohol Fast Bacilli (AAFB) staining and culture, using Ziehl-Neelsen (ZN) method - red dots on a blue background.

• Take 4-7 weeks for +ve and further 3 weeks for sensitivities.


  Treatment

Triple combo therapy


• Initial Phase (8/52 on 3-4 drugs)

Rifampicin 600-900 mg (kid 15 mg/kg) PO 3x/wk

Isoniazid 15 mg/kg PO 3x/wk + Pyridoxine  10 mg/24 hr

Pyrazinamide 2.5 PO (2 g if <50 kg) 3x/wk (kid 50 mg/kg)

• If resistance possible add Ethambutol 30 mg/kg PO 3x/wk

• Or Streptomycin 0.75 - 1 g/24 hr (kid 15 mg/kg/24hr)

Monitor LFTs weekly


Continuation Phase (4/12 on 2 drugs)

Rifampicin and Isoniazide @ same doses

• (2 Rifinah 300 tablets = 600 mg Rifampicin + Isoniazide 300 mg)

• If resistance is a problem => Ethambutol 30 mg/kg 3x/wk

• Pyridoxine throughout treatment

• Steroids may be indicated in meningeal and pericardial disease


• Directly observed therapy if needed

• Pyridoxine (10 mg/day) to prevent neuropathy for those at risk (isoniazid cause)


Testing

• Heaf or Mantoux


Control

• Patients considered potentially infectious until 2/52 treatment completed

• Notifiable disease (to Public health Authorities -> screening of contacts).

• 10% of close contacts of smear-positive cases found to have active disease

Chemoprophylaxis

6/12 of Isoniazid alone

3/12 of Isoniazid and Rifampicin


BCG Vaccination


• Oppoturnistic Mycobacteria (Atypical) - low-grade pathogens, but require long-term (2 years) treatment.