Tuberculosis: Basics

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Tuberculosis Basics

• Rick Speare
• Anton Breinl Centre
• School of Public Health, Tropical Medicine and
  Rehabilitation Sciences
• James Cook University

16 May 2011
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Objectives

• To provide background on TB to assist
  understanding of tuberculosis and control
  strategies

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Tuberculosis

• Due to the bacterium, Mycobacterium tuberculosis
• Small due to M. bovis
• Pulmonary disease bloodstream spread to other
  organs
• Bacilli are coughed up and inhaled by others
• All ages can develop disease
• Infection can be acquired in childhood, remain
  latent and emerge as immunity wanes

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Transmission

• Droplet transmission is usual route
• Mycobacterium aerosolised into droplets
  (coughing, speaking, breathing)
• Inhaled into alveoli of new host
• Grows in alveoli (Ghon focus)
• Carried to bronchial lymph nodes (Ghon complex)
• M. bovis can also be spread in milk from infected
  bovine udders

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Histology of the normal alveolae

• http//www.anatomy.dal.ca/Human20Histology/Lab11/
  59ll4la.html

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Histopathology of TB granuloma
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Risk of Transmission

• People in close contact with TB case have highest
  risk of infection (clustered)
• Transmission can result from casual and brief
  contact in highly endemic areas
• South African studies demonstrated this (Verver
  et al 2004)
• Greater risk when number of bacteria are higher
• Risk of transmission falls rapidly with treatment

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• http//www.health.vic.gov.au/ideas/diseases/tb_com
  munity

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Pulmonary TB

• Chronic cough
• Productive
• Haemoptysis
• Weight loss
• Night sweating

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Fatal pulmonary TB Prisoner in Lilongwe, Malawi
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Very severe consolidation, caseating necrosis and
cavities
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Another Malawaian patient with pulmonary TB and
cavities
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(No Transcript)
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• Consolidation
• Cavities

TB is a very destructive disease Diagnose
treat early!
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Death from TB

• Respiratory failure
• Severe haemoptysis
• Systemic TB (miliary TB)
• Meningeal TB
• Other

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Severe haemoptysis patient often drowns in their
own blood
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Very destructive disease

• Cavities due to patient coughing up necrotic lung
• Fibrosis is common
• Damaged tissue can not be replaced
• Diagnose and treat early!

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Healed Cavity
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TB is mainly a pulmonary disease, but
extra-pulmonary disease is common

• Bacteraemia with seeding of multiple organs
  (miliary TB)
• Localised infection in any other organ
• Meningitis
• Osteomyelitis
• Arthritis
• Lymph node infection
• Other

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TB meningitis infants AIDS
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Osteomyelitis

• Arthritis

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Osteomyelitis of spine
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Diagnosis of pulmonary TB

• Detection of Mycobacterium tuberculosis in
  sputum
• Culture of sputum
• Smear of sputum
• Acid fast bacilli (stained with acid fast stain)
• PCR

Pulmonary TB can not be diagnosed from a chest
X-ray
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TB Disease control

• The focus in control of TB is only on the person
  spreading TB
• Sputum positive case only (AFB Sm)
• Other cases are of minor significance in control
  of TB

Sometimes, clinical aims and TB control aims clash
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Breaking Transmission

• Droplet transmission is usual route
• Points to break the transmission cycle
• Preventing viable Mycobacterium getting into
  droplets
• Preventing droplets with Mycobacterium getting
  into the alveoli of a new host
• Preventing Mycobacterium in alveoli from causing
  disease