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
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To provide background on TB to assist
understanding of tuberculosis and control
strategies
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Tuberculosis
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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
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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
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http://www.anatomy.dal.ca/Human%20Histology/Lab11/59ll4la.html
Histopathology of TB granuloma
Risk of Transmission
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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
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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_community
Pulmonary TB
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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
Another Malawaian patient with
pulmonary TB and cavities
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Consolidation
Cavities
TB is a very destructive
disease
Diagnose & treat early!
Death from TB
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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
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Cavities due to patient coughing up necrotic
lung
Fibrosis is common
Damaged tissue can not be replaced
Diagnose and treat early!
“Healed” Cavity
TB is mainly a pulmonary
disease, but extra-pulmonary
disease is common
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Bacteraemia with seeding of multiple organs (miliary
TB)
Localised infection in any other organ
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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
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Detection of Mycobacterium tuberculosis
in sputum
Culture of sputum
Smear of sputum
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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
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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
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Droplet transmission is usual route
Points to break the transmission cycle:
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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
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