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Tuberculosis
Partners in Global Health Education
How to use this module
Learning outcomes
What is TB?
Welcome to the tuberculosis (TB)
module.
Epidemiology
Microbiology
Transmission
Section 1 quiz
Natural history
Section 2 quiz
Symptoms and signs
Section 3 quiz
Diagnosis
Treatment
Prevention and control
Section 4 quiz
Information sources
TB is a major cause of morbidity
and mortality all over the world but
the greatest burden is borne by
developing countries. The
bacterium Mycobacterium
tuberculosis is responsible for most
TB cases.
Summative assessment
For more information about the authors and
reviewers of this module, click here
IUATLD; WHO/TBP/Falise
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How should you study this module?
Partners in Global Health Education
•
How to use this module
Learning outcomes
What is TB?
Epidemiology
•
•
Microbiology
Transmission
Section 1 quiz
•
Natural history
Section 2 quiz
Symptoms and signs
Section 3 quiz
•
Diagnosis
Treatment
•
Prevention and control
Section 4 quiz
Information sources
•
Summative assessment
•
We suggest that you start with the learning objectives and try to
keep these in mind as you go through the module slide by slide,
in order.
Print-out the mark sheet
As you go along, write your answers to the questions on the
mark sheet as best you can before looking at the answers.
Award yourself marks as detailed on the mark sheet: one mark
for each keyword (shown in red text) in the short answer
questions and for every correct answer in the True/False
questions.
Repeat the module until you have achieved a mark of 28/35
(≥80%).
Finish with the formative multiple choice questionnaire to assess
how well you have covered the material as a whole.
You should research any issues that you are unsure about. Look
in your textbooks, access the on-line resources indicated at the
end of the module and discuss with your peers and teachers.
Finally, enjoy your learning! We hope that this module will be
enjoyable to study and complement your learning about TB from
other sources.
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Learning Outcomes
Partners in Global Health Education
How to use this module
By the end of the module, you should be able to:
Learning outcomes
What is TB?
1.
Describe how TB can affect anyone, of any age, anywhere, but that
most cases occur in specific risk groups
2.
Describe how respiratory droplets are the main transmission agent
3.
Describe how, following inhalation, M. tuberculosis causes infection in
many people and disease in some
4.
Enumerate the general symptoms and signs of TB and the specific
clinical features of pulmonary TB
5.
Discuss how CXR and sputum examination are used in diagnosis
6.
Describe how TB is managed using combinations of antimicrobials
7.
Describe how TB is prevented at the community level by immunisation,
case finding and contact tracing
Epidemiology
Microbiology
Transmission
Section 1 quiz
Natural history
Section 2 quiz
Symptoms and signs
Section 3 quiz
Diagnosis
Treatment
Prevention and control
Section 4 quiz
Information sources
Summative assessment
What is tuberculosis (TB)?
Partners in Global Health Education
How to use this module
Learning outcomes
What is TB?
Epidemiology
Microbiology
Transmission
Section 1 quiz
Natural history
Section 2 quiz
Symptoms and signs
Section 3 quiz
Diagnosis
Treatment
Prevention and control
Section 4 quiz
Information sources
Summative assessment
TB is a chronic bacterial infection. The great majority of infections in
people are caused by Mycobacterium tuberculosis (M.
tuberculosis). A closely related bacteria, M. bovis, causes TB in
animals (especially cattle) and can infect people who drink
unpasteurised milk from infected cows.
Although an ancient disease, TB
remains a world wide problem:
• about 1 in 3 of the world’s
population is infected with tubercle
bacilli and someone is newly
infected every second
• although most infected people
remain asymptomatic, there are
about 9 million new cases and
nearly 2 million TB deaths every
year.
Where does TB occur?
Epidemiology 4
Partners in Global Health Education
How to use this module
Learning outcomes
What is TB?
Epidemiology
Microbiology
Transmission
Section 1 quiz
Natural history
Section 2 quiz
Symptoms and signs
Section 3 quiz
Diagnosis
Treatment
Prevention and control
Section 4 quiz
Information sources
Summative assessment
About 95% of the world’s cases of TB occur in South East Asia, subSaharan Africa and the Western Pacific.
The largest number of cases and
highest mortality occur in South East
Asia and this region accounts for 33%
of incident cases globally.
The annual incidence of TB is
increasing sub-Saharan Africa mainly
as a result of the increased
susceptibility of people infected with
HIV.
Other factors which encourage TB
transmission are:
• the emergence of multidrug-resistant strains of M. tuberculosis
• poor national TB control programmes and worsening socio-economic
conditions in many countries
In the UK, the annual incidence rate is increasing with >8,000 new
cases/year. Most occur in the larger cities, especially London, and
about 2/3 cases occur in people who were born abroad. TB causes
or contributes to 300-400 deaths/year in the UK.
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Microbiology (1)
Partners in Global Health Education
How to use this module
Learning outcomes
What is TB?
Epidemiology
Microbiology
Transmission
Section 1 quiz
Natural history
Section 2 quiz
Symptoms and signs
M. tuberculosis is a non-motile, rod-shaped
bacterium measuring 2-4 x 0.2-0.5 μm. It is
an obligate aerobe, which explains why it
tends to be found in the well-aerated, upper
lobes of the lungs.
It is a slow growing organism (dividing only
every 16-20 hours) that lives within tissue
macrophages. Humans are the only
reservoir of M. tuberculosis. Both animals
and humans serve as reservoirs for M.
bovis.
Section 3 quiz
Diagnosis
Treatment
Prevention and control
Section 4 quiz
Information sources
Summative assessment
The organism does not have the
characteristics of either Gram positive or
negative bacteria. It has a peculiar cell wall
that consists of peptidoglycan and complex
lipids. Once stained (e.g. with carbol
fuchsin), the organism will retain dyes when
treated by acidified organic compounds.
Therefore, it is classified as an “acid–fast”
bacterium.
The Ziehl-Nielsen stain is
used to demonstrate the
presence of the bacilli in a
smear. Note the bright red
rods in this sputum smear.
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Microbiology (2)
Partners in Global Health Education
How to use this module
Learning outcomes
What is TB?
Epidemiology
Microbiology
Transmission
The cell wall is a major factor in the virulence of the organism.
It resists destruction by many
antibiotics, acids, alkalis, osmotic
lysis and oxidation and enables
the organism to survive and
multiply within macrophages.
Section 1 quiz
Natural history
Section 2 quiz
Symptoms and signs
Section 3 quiz
Diagnosis
Treatment
Prevention and control
Section 4 quiz
Information sources
Summative assessment
M. tuberculosis grows in
Lowenstein Jensen medium, an
egg-based medium, which
contains inhibitors to keep
contaminants from outgrowing the
organism. Because of its slow
growth, it takes 4-6 weeks before
small buff-coloured colonies are
visible on the medium.
Typical small, buff coloured colonies of
M. tuberculosis on Lowenstein Jensen
medium
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How is TB transmitted?
How to use this module
Learning outcomes
What is TB?
Epidemiology
Microbiology
Transmission
Section 1 quiz
Natural history
Section 2 quiz
Symptoms and signs
Section 3 quiz
Diagnosis
Treatment
Prevention and control
Section 4 quiz
Information sources
Partners in Global Health Education
Nearly all TB infection is acquired by inhalation of respiratory
droplets from people with TB in the lungs or throat.
Air droplets 3-5 μm
diameter are coughed,
sneezed or spat-out by an
“open” case of TB. The
droplets are inhaled by a
close contact. This is
more likely to occur in
overcrowded
environments.
Summative assessment
NB. Abdominal TB can also result from drinking unpasteurised
cow’s milk infected with M. bovis.
End of Section 1
How to use this module
Learning outcomes
What is TB?
Epidemiology
Partners in Global Health Education
Well done!
You have come to the end of the first section.
Microbiology
Transmission
Section 1 quiz
Natural history
Section 2 quiz
Symptoms and signs
Section 3 quiz
Diagnosis
Treatment
Prevention and control
Section 4 quiz
Information sources
Summative assessment
We suggest that you answer questions 1 to assess your
learning so far. Please remember to write your answers on
the mark sheet before looking at the correct answers!
Question 1: Risk of exposure to TB
Write “True” or “False” on the answer sheet.
When you have completed all 5 questions, click on the boxes and mark your answers.
How to use this module
Learning outcomes
Now that you know how TB is transmitted, are the following
people at increased risk of exposure?
Click for the correct
answer
What is TB?
Epidemiology
Microbiology
Transmission
a)
Section 2 quiz
Symptoms and signs
Section 3 quiz
b)
People who drink unpasteurised milk
c)
People living in poor, overcrowded
Diagnosis
environments
Treatment
Prevention and control
d)
Section 4 quiz
a
People who work or are residents in long-
b
c
d
term facilities
Information sources
Summative assessment
Close contacts of people with open TB (e.g.
family members)
Section 1 quiz
Natural history
Partners in Global Health Education
e)
Infants and young children
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What happens following inhalation of M. tuberculosis?
Outcome 1: No infection
How to use this module
Learning outcomes
What is TB?
Partners in Global Health Education
Between 70-90% of individuals exposed to TB will not
develop the infection.
Epidemiology
Microbiology
Transmission
Section 1 quiz
Natural history
The reasons for this are unclear. However, in view of the
known risk factors for infection, people who inhale
bacilli but do not develop an infection may:
Section 2 quiz
Symptoms and signs
Section 3 quiz
Diagnosis
Treatment
•
•
inhale too few organisms to cause infection
have sufficient immunity to prevent an infection
becoming established
Prevention and control
Section 4 quiz
Information sources
Summative assessment
Any factor associated with impaired immunity, such as
extremes of age, malnutrition and HIV/AIDS will
increase the risk of developing infection.
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What happens following inhalation of M. tuberculosis?
Outcome 2: Infection with formation of a primary complex
How to use this module
Learning outcomes
What is TB?
Epidemiology
Microbiology
Partners in Global Health Education
Following inhalation, tubercle bacilli settle in the alveoli
and result in local inflammation in the lung
parenchyma. This “primary focus” usually occurs in
the upper lobes in adults but may occur in any of the
lung lobes in children. More than one focus may occur
in the same patient.
Transmission
Section 1 quiz
Natural history
Section 2 quiz
Symptoms and signs
Section 3 quiz
Diagnosis
Treatment
Prevention and control
Section 4 quiz
Information sources
Summative assessment
The organisms then spread via the local lymphatics to
the nearest hilar lymph nodes, which may then
enlarge.
The primary focus and the enlarged regional lymph
nodes form the “primary complex” or “Ghon
complex”.
What happens next depends on the size of the
infecting dose and the resistance of the host. Most
commonly, the primary focus is “walled-off” by the
immune system and lies dormant– “latent TB”. The
infection may be reactivated years later if the immune
system of the host becomes weakened.
Primary focus successfully
contained by the host immune
system
The person is infected but does not
have TB disease and cannot
spread TB. However, an immune
response to M. tuberculosis will
have developed – and can be
demonstrated by a positive
Mantoux test (see later).
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What happens following inhalation of M. tuberculosis?
Outcome 3: Pulmonary disease
How to use this module
Learning outcomes
What is TB?
Epidemiology
Microbiology
Transmission
Section 1 quiz
Natural history
Section 2 quiz
Symptoms and signs
Section 3 quiz
Diagnosis
Treatment
Prevention and control
Section 4 quiz
Information sources
Summative assessment
If the primary focus is not contained, lung disease may
develop in several ways:
•
The primary focus enlarges and undergoes central
necrosis to form a cavity
•
The infection can spread locally and result in
tuberculous bronchopneumonia
•
Marked swelling of the mediastinal lymph nodes may
compress large bronchi and result in lobar collapse
•
The enlarged lymph node may act like a one-way
valve causing hyperinflation of a lung or lobe
•
The adjacent pleura can become infiltrated by M.
tuberculosis resulting in a hypersensitivity reaction
characterised by granulomas composed mainly of
lymphocytes
•
Pleural infiltration may result in a pleural effusion
which is rich in lymphocytes – a useful pointer to the
diagnosis when pleural fluid is aspirated and
analysed
•
Long term complications of the damage to lung tissue
include emphysema and bronchiectasis
Partners in Global Health Education
Infection not contained by
the immune system.
Person develops lung
disease and becomes an
open case - capable of
infecting others via
respiratory droplets.
What happens following inhalation of M. tuberculosis?
Pathogenesis 4
Outcome 4: Systemic disease
How to use this module
Learning outcomes
What is TB?
Epidemiology
Microbiology
Transmission
Section 1 quiz
Natural history
Section 2 quiz
Symptoms and signs
Section 3 quiz
Diagnosis
Treatment
Haematogenous dissemination of M.
tuberculosis leads to granuloma formation in
many organs. Examples include:
• Diffuse infection of the lungs: “miliary” TB
• Brain: TB brain abscess
• Meninges: TB meningitis
• Bones: TB osteomyelitis – commonly affects
the spine and is then called “Potts’ disease”
• Pericardium: TB pericarditis and pericardial
effusion
Prevention and control
Section 4 quiz
Information sources
Summative assessment
As with acquiring infection after inhalation,
disseminated disease is most likely to occur in
the immunocompromised person (e.g.
HIV/AIDS, malnutrition) and at extremes of age.
Partners in Global Health Education
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Summary (1): natural history following TB
exposure
Partners in Global Health Education
How to use this module
What are the likely outcomes following exposure to open TB?
Learning outcomes
What is TB?
Exposure to TB
Epidemiology
Microbiology
Transmission
Section 1 quiz
Natural history
Section 2 quiz
Symptoms and signs
No infection
(70-90%)
Infection
(10-30%)
Section 3 quiz
Diagnosis
Treatment
Prevention and control
Section 4 quiz
Information sources
Summative assessment
Dormant TB (90%)
• well
• no TB disease
• not infectious to
others
Active TB (10%)
• ill and likely to die if
untreated
• infectious
Activation of infection
results in disease
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Summary (2): natural history following TB exposure
Partners in Global Health Education
How to use this module
Learning outcomes
What is TB?
There are 4 possible outcomes following inhalation of TB bacilli:
Epidemiology
Microbiology
Transmission
Outcome
Person
unwell?
Person
transmits
disease?
Person develops
an immune
response to TB?
1: No infection
No
No
No
2. 1o lung complex
No
No
Yes
3. Pulmonary disease
Yes
Yes
Yes
4: Systemic disease
Yes
Yes
Yes
Section 1 quiz
Natural history
Section 2 quiz
Symptoms and signs
Section 3 quiz
Diagnosis
Treatment
Prevention and control
Section 4 quiz
Information sources
Summative assessment
Note: outcomes 3 and 4 can develop many years after formation of the 1o lung
complex
End of Section 2
How to use this module
Learning outcomes
What is TB?
Epidemiology
Partners in Global Health Education
Well done!
You have come to the end of the second section.
Microbiology
Transmission
Section 1 quiz
Natural history
Section 2 quiz
Symptoms and signs
Section 3 quiz
Diagnosis
Treatment
Prevention and control
Section 4 quiz
Information sources
Summative assessment
Answer questions 2 through 4 to assess your learning so
far. Challenge yourself: complete the mark sheet before
looking at the correct answers!
Question 2: Groups of people at increased risk of TB disease
and disseminated infection following exposure are:
Write “True” or “False” on the answer sheet.
Partners in Global Health Education
Click for the
correct answer
How to use this module
Learning outcomes
What is TB?
a)
Infants and children <5 years
a
b)
People with HIV/AIDS
b
c)
People with diabetes mellitus, measles,
Epidemiology
Microbiology
Transmission
Section 1 quiz
Natural history
Section 2 quiz
Symptoms and signs
pertussis or on prolonged corticosteroid therapy
Section 3 quiz
Diagnosis
Treatment
Prevention and control
d)
Young adults
e)
Alcoholics and IV drug users
c
d
Section 4 quiz
Information sources
Summative assessment
e
Question 3: Factors underlying the resurgence of TB in
the last 2 decades are:
Write “True” or “False” on the answer sheet.
Partners in Global Health Education
Click for the
correct answer
How to use this module
Learning outcomes
What is TB?
a)
HIV pandemic
a
b)
Poverty/worsening socioeconomic conditions
b
c)
Poor hygiene
c
d)
Emergence of drug resistance strains
d
e)
Poor national TB control programmes
e
Epidemiology
Microbiology
Transmission
Section 1 quiz
Natural history
Section 2 quiz
Symptoms and signs
Section 3 quiz
Diagnosis
Treatment
Prevention and control
Section 4 quiz
Information sources
Summative assessment
Question 4: Following exposure to M. tuberculosis
Write “True” or “False” on the answer sheet.
Partners in Global Health Education
Click for the
correct answer
How to use this module
Learning outcomes
What is TB?
a)
The usual outcome is a primary
infection
a
b)
The primary complex consists of a
cavity in the lung parenchyma and
hilar lymphadenopathy
b
c)
A pleural aspirate rich in neutrophils
suggests TB as a cause
c
d)
Miliary TB refers to disseminated
infection spread via the bloodstream
d
Epidemiology
Microbiology
Transmission
Section 1 quiz
Natural history
Section 2 quiz
Symptoms and signs
Section 3 quiz
Diagnosis
Treatment
Prevention and control
Section 4 quiz
Information sources
Summative assessment
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What are the symptoms and signs of TB?
1. Primary infection with no spread of the disease
How to use this module
Learning outcomes
What is TB?
Epidemiology
Microbiology
Transmission
Section 1 quiz
Natural history
Section 2 quiz
Symptoms and signs
Section 3 quiz
Diagnosis
Treatment
Prevention and control
Section 4 quiz
Information sources
Summative assessment
Individuals with primary infection do not
usually have any symptoms or signs of ill
health although some people develop a
minor flu-like illness.
Infection triggers an immune response
and, in a minority of people, this may
result in clinical signs of hypersensitivity
to M. tuberculosis for example:
• erythema nodosum
• phlyctenular keratoconjunctivitis
They will also have a positive Mantoux
test (see below).
Partners in Global Health Education
Erythema nodosum:
ecchymotic papules found
along the shin or on the
flexural surfaces of the limbs
Phlyctenular
keratoconjunctivitis: raised,
yellowish nodule at the
corneoscleral junction. Small
blood vessels may be seen
radiating from the nodule.
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What are the symptoms and signs of TB?
2. Active infection: symptoms
How to use this module
Learning outcomes
What is TB?
Epidemiology
Microbiology
Transmission
Section 1 quiz
Natural history
Symptoms of TB can be divided
into general symptoms and those
specific to the organ infected.
TB can result in a myriad of
symptoms depending on which
organs are involved and how their
function is affected.
Section 2 quiz
Symptoms and signs
Section 3 quiz
Diagnosis
The lung is the predominant
organ affected, being involved in
over 75% of cases.
Treatment
Prevention and control
Section 4 quiz
Information sources
Summative assessment
Commonly affected organs
following haematogenous spread
from the lung are the abdomen,
lymph nodes, spine, meninges,
kidneys, bone and reproductive
organs.
Partners in Global Health Education
General symptoms
• Fever
• Loss of weight in adults or growth
faltering in children
• Night sweats
• Malaise, tiredness and anorexia
Organ specific - examples include:
Lungs
• Cough – usually chronic (lasting >6
weeks)
• Productive of whitish or mucoid sputum
in adults but usually unproductive in
children
• Haemoptysis (coughing-up blood)
Central Nervous System
• TB meningitis
• Tuberculoma, with the classical features
of a space-occupying lesion simulating a
brain tumour
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What are the symptoms and signs of TB?
2. Active infection: signs
Partners in Global Health Education
How to use this module
Learning outcomes
What is TB?
Epidemiology
Microbiology
Transmission
Section 1 quiz
General examination - look for:
• fever
• signs of malnutrition signifying a chronic illness
• enlargement of the peripheral lymph nodes
• digital clubbing as a consequence of chronic
infection/inflammation in the chest or abdomen
Natural history
Section 2 quiz
Symptoms and signs
Section 3 quiz
Diagnosis
Treatment
Prevention and control
Section 4 quiz
Information sources
Summative assessment
TB lymphadenitis presents as painless
enlargement of the superficial lymph nodes. The
neck is the commonest site involving the cervical,
submandibular, pre and post-auricular lymph
nodes. The lymph nodes are non-tender, matted
together and rubbery in consistency. It is common
for enlarged lymph nodes to ulcerate and
discharge.
Look at this picture of a 4 year old boy from West
Africa. Note that he is generally wasted and has
marked enlargement of the cervical lymph nodes
– especially on the right side.
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What are the symptoms and signs of TB?
3. Pulmonary and abdominal TB
Partners in Global Health Education
Pulmonary TB (PTB)
How to use this module
Learning outcomes
What is TB?
Epidemiology
Microbiology
The apical region is the most
commonly affected in adults.
Pulmonary lesions may involve any
part of the lung in infancy and
childhood.
Transmission
Section 1 quiz
Natural history
Section 2 quiz
Symptoms and signs
Section 3 quiz
Diagnosis
Treatment
Prevention and control
Abnormalities detected clinically
include consolidation, collapse,
pleural effusion and fibrosis. But
beware: examination of the
respiratory system may be
completely normal even in active
disease!
Abdominal TB
Upper lobe changes on CXR
Source: WHO/TBP/Pierre Virot
Section 4 quiz
Information sources
Summative assessment
Pathology affects the mesenteric and the retroperitoneal glands, the omentum and
the gastrointestinal tract. Patients may present with weight loss, diarrhoea or
constipation, abdominal distension (from ascites) or chronic intestinal obstruction.
Enlarged mesenteric lymph nodes may be palpable as multiple intra-abdominal
masses.
Tuberculosis of the spine – “Pott’s disease”
Partners in Global Health Education
How to use this module
TB commonly affects the spine,
especially in young children, and
usually presents as a swelling on the
back.
Learning outcomes
What is TB?
Epidemiology
Microbiology
The lower thoracic and the upper
lumbar vertebrae are the usual sites,
however any vertebra can be
affected.
Transmission
Section 1 quiz
Natural history
Section 2 quiz
The patient may also present with
kyphosis, scoliosis, kyphoscoliosis,
or features of spastic paraparesis.
There may be a sharp angulation of
the spine caused by collapse of a
vertebra – referred to as a “gibbus”
Symptoms and signs
Section 3 quiz
Diagnosis
Treatment
Prevention and control
Section 4 quiz
Information sources
Summative assessment
A young child from West
Africa. Note the swelling over
the lower thoracic vertebrae.
End of Section 3
How to use this module
Learning outcomes
What is TB?
Epidemiology
Partners in Global Health Education
Well done!
This is the end of the second section.
Microbiology
Transmission
Section 1 quiz
Natural history
Section 2 quiz
Symptoms and signs
Section 3 quiz
Diagnosis
Treatment
Prevention and control
Section 4 quiz
Information sources
Summative assessment
We suggest that you proceed to answer question 5 to
assess your learning further. Do remember to write your
answers on the mark sheet before looking at the right
answer!
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Question 5: What 2 features are consistent with
pulmonary TB in this man?
Partners in Global Health Education
How to use this module
Learning outcomes
What is TB?
Epidemiology
Microbiology
Transmission
Section 1 quiz
Natural history
Section 2 quiz
Symptoms and signs
Section 3 quiz
Diagnosis
Treatment
Write Down Your
Answers on your
mark sheet, then
click below to reveal
the answers
Prevention and control
Section 4 quiz
Information sources
Summative assessment
Man with advanced TB in Bangladesh
source: WHO/TBP/England
Click to Reveal Answers
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Diagnosis
Partners in Global Health Education
How to use this module
Learning outcomes
What is TB?
In developing countries, the diagnosis
of TB is based on the combination of
clinical assessment and simple
laboratory methods:
Epidemiology
Microbiology
Transmission
Section 1 quiz
Natural history
Section 2 quiz
Symptoms and signs
Section 3 quiz
Diagnosis
1. History of chronic cough with the
general symptoms of fever, malaise
and weight loss
2. Presence of general and specific
clinical signs
3. Positive findings on relevant
investigations – usually CXR and
sputum smear stained for acid-fast
bacilli
Treatment
Prevention and control
Section 4 quiz
It is important to note that specific
symptoms and signs may be absent.
Examining a CXR in China
Source: WHO/TBP/Pierre Virot
Information sources
Summative assessment
TB should be suspected in any chronically ill person!
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Bacteriological diagnosis
Partners in Global Health Education
•
Sputum microscopy is most useful in
adults with a productive cough. A sputum
smear is stained with the Ziehl-Nielsen
stain to demonstrate the presence of the
acid and alcohol fast bacilli (AFB). When
positive, the patient is “smear-positive” or
“open TB” and the risk of transmission of
infection to others is very high. However,
the test is often falsely negative in patients
with TB. The yield of the test is higher in
patients with lung cavities.
•
Gastric washings examined for AFB:
Carried out in children as they swallow
rather than cough-up sputum. The test aims
to recover the swallowed AFB from the
stomach using a naso-gastric tube. The test
is positive in only about one third of
children with TB.
How to use this module
Learning outcomes
What is TB?
Epidemiology
Microbiology
Transmission
Section 1 quiz
Natural history
Section 2 quiz
Symptoms and signs
Section 3 quiz
Diagnosis
Treatment
Prevention and control
Section 4 quiz
Information sources
Summative assessment
•
Bacterial culture: This takes about 6-8
weeks and so is of limited use in clinical
diagnosis. M. tuberculosis grows on a
special medium called the Lowenstein
Jensen medium.
Sputum samples collected in a
health facility in Ethiopia
source: WHO/TBP/Jan Van den
Hombergh
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Mantoux or tuberculin skin test
Partners in Global Health Education
How to use this module
Learning outcomes
What is TB?
Epidemiology
Microbiology
Transmission
This test detects a delayed hypersensitivity, cutaneous reaction to a purified
protein derivative (PPD) of M. tuberculosis – also called “tuberculoprotein”:
1. PPD is injected intradermally
2. the injection site is inspected 48-72 hours later
3. erythema and induration at the site signify an immune response and,
therefore, previous exposure to mycobacteria
Section 1 quiz
Natural history
Section 2 quiz
Symptoms and signs
Section 3 quiz
Diagnosis
Treatment
Prevention and control
Section 4 quiz
Information sources
Summative assessment
The limitations of this test are well-known:
 False positive: a skin reaction in people who do not have TB because of
exposure to non-pathogenic mycobacteria and also due to the immune
response following BCG immunisation (see later).
 False negative: a negative result in a person with TB in early primary
infection or because they are immunocompromised – for example, due to
HIV/AIDS, malnutrition or people who develop disseminated TB.
In general, the greater the degree of erythema and induration, the more likely
the patient has TB disease. Several detailed criteria are available to guide
the interpretation of Mantoux results, e.g. from the American Thoracic
Society and Centers for Disease Control & Prevention
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Diagnosis: Other investigations
Partners in Global Health Education
How to use this module
Learning outcomes
What is TB?
Epidemiology
Microbiology
Transmission
Section 1 quiz
Natural history
Other investigations are indicated depending on the organs/ systems
affected by the disease
 Spinal radiographs in Pott’s disease
 Lymph node aspirate (microscopy, culture and cytology) or biopsy
(histology and culture) in TB lymphadenitis
 Lumbar puncture for cerebrospinal fluid analysis in TB meningitis
(microscopy, biochemical analysis and culture)
Section 2 quiz
Symptoms and signs
Section 3 quiz
Diagnosis
Treatment
Prevention and control
Section 4 quiz
Information sources
Summative assessment
A recent development is the detection of the growth of TB in liquid
culture by microscopy. Diagnosis can be made within 10 days and
addition of drugs to the cultures allows the detection of drug
resistance.*
Also, a number of new diagnostic tests have been developed based
on molecular methods such as the amplification of nucleic-acid.
However, these assays have not been fully evaluated and are
expensive.
* Moore DA et al. Microscopic-observation drug-susceptibility assay for the diagnosis of
TB. N Engl J Med 2006; 355:1539-50
Treatment
Partners in Global Health Education
How to use this module
Learning outcomes
What is TB?
Resistance of M. tuberculosis to antimicrobials is a major
problem in TB treatment. Because it is a slow growing
organism, treatment courses are long - at least 6 months.
Epidemiology
Microbiology
Transmission
Section 1 quiz
Natural history
Section 2 quiz
Symptoms and signs
Section 3 quiz
Diagnosis
Treatment
• Treatment requires a
combination of drugs to which
the organisms are sensitive.
• Treatment courses must be
completed for effective cure
and to prevent the emergence
of drug-resistant strains.
Prevention and control
Section 4 quiz
Information sources
Summative assessment
• Longer treatment courses are
needed for TB meningitis or if
the bacteria are resistant and
additional drugs are required.
Combination antibiotic therapy
in India
Source: IUTBLD WHO/TBP/Gary
Hampton
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Treatment: DOTS
Partners in Global Health Education
How to use this module
Learning outcomes
What is TB?
Epidemiology
Microbiology
DOTS is the acronym for Directly Observed Treatment Short Course.
It involves the daily administration of a combination of antituberculous drugs to
a TB patient under the supervision of a healthcare personnel. DOTS helps to
ensure compliance, reduce transmission by shortening the period of infectivity,
improve the cure rate and reduce the risk of drug resistance.
Transmission
Section 1 quiz
Natural history
There are many regimens for treating TB. The most frequently recommended
regimen that is also effective in people with HIV infection is:
Section 2 quiz
Symptoms and signs
Drug
0-2 months
3-6 months
Section 3 quiz
Diagnosis
Isoniazid
+
+
Treatment
Rifampicin
+
+
Section 4 quiz
Pyrazinamide
+
-
Information sources
Ethambutol*
+
-
Prevention and control
Summative assessment
*IM streptomycin is often substituted for oral ethambutol for children < 6 years
Drug-resistant TB
Partners in Global Health Education
How to use this module
Learning outcomes
What is TB?
Epidemiology
Microbiology
Transmission
Section 1 quiz
Natural history
Section 2 quiz
There are 2 classes of drug resistant TB:
1. Multidrug-resistant (MDR)
• defined as resistance to rifampicin and isoniazid, +/- other
drug resistance
• worldwide, >4% of TB patients are MDR, with the highest
prevalence in Eastern Europe
• treatment requires longer drug regimens, is less effective,
more costly and poorly tolerated
Symptoms and signs
Section 3 quiz
Diagnosis
Treatment
Prevention and control
Section 4 quiz
Information sources
Summative assessment
2. Extensively drug-resistant (XDR)
• defined as resistance to rifampicin and isoniazid and, in
addition, resistance to any quinolone and at least on
injectable second-line drug
• XDR TB is essentially untreatable and has a very high
mortality
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Prevention and Control
Partners in Global Health Education
How to use this module
Learning outcomes
What is TB?
TB control strategies include –
• Case finding: aims to identify TB cases promptly, treat them
with an effective combination of drugs and ensure that the
course is completed.
Epidemiology
Microbiology
Transmission
•
Contact tracing: Close contacts of TB cases are screened for
evidence of infection. Mantoux positive cases are treated with
oral isoniazid for 6-12 months to prevent them from developing
the disease. This regimen is also used in HIV-positive people.
•
Bacillus Calmette-Guérin (BCG) vaccine
• contains an attenuated strain of M. bovis
• is administered as a single intradermal injection
• Has limited efficacy against pulmonary TB (and, therefore,
TB transmission) but does appear to prevent disseminated
disease and death – especially in children
• is given routinely to infants in developing countries and to
people at increased risk of TB infection in developed
countries
Section 1 quiz
Natural history
Section 2 quiz
Symptoms and signs
Section 3 quiz
Diagnosis
Treatment
Prevention and control
Section 4 quiz
Information sources
Summative assessment
TB: the future
Partners in Global Health Education
How to use this module
Learning outcomes
What is TB?
•
Epidemiology
Microbiology
Transmission
Section 1 quiz
Natural history
•
Section 2 quiz
Symptoms and signs
Section 3 quiz
Diagnosis
Treatment
•
Prevention and control
Section 4 quiz
Information sources
Summative assessment
•
WHO declared TB a global health emergency in 1993 and aims to
eliminate TB as a public health problem by 2050.
Other organisations involved in TB
control include the International Union
Against TB and Lung Disease, the
Center for Disease Control (USA) and
the Global Plan to Stop TB.
TB remains a worldwide challenge.
There is a need to improve DOTS
coverage and meet the emerging
challenges of TB in people with
HIV/AIDS and multidrug resistant TB.
Improved techniques for diagnosis are
required especially in people with
compromised immunity where diagnosis
is difficult such as HIV/AIDS and
malnourished children.
A more effective vaccine and improved
treatment strategies that would decrease
the duration of treatment are also high
IUATLD; WHO/TBP/Falise
priorities.
End of Section 4
How to use this module
Learning outcomes
What is TB?
Epidemiology
Partners in Global Health Education
You have come a long way!
This is the last of the sections.
Microbiology
Transmission
Section 1 quiz
Natural history
Section 2 quiz
Symptoms and signs
Section 3 quiz
Diagnosis
Treatment
Prevention and control
Section 4 quiz
Information sources
Summative assessment
For the section just ended, you should be able to answer
Questions 6 - 8 to assess what you have learnt. It is still
required that you put down your answers on the mark
sheet before looking at the right answer!
Question 6: A person with latent TB
Write “True” or “False” on the answer sheet.
Partners in Global Health Education
Click for the
correct answer
How to use this module
Learning outcomes
What is TB?
a)
Is infectious to other people
a
b)
Feels well
b
c)
Tuberculin skin test is positive
c
d)
Can not develop TB later in life
d
Epidemiology
Microbiology
Transmission
Section 1 quiz
Natural history
Section 2 quiz
Symptoms and signs
Section 3 quiz
Diagnosis
Treatment
Prevention and control
Section 4 quiz
Information sources
Summative assessment
Question 7: The following are recognised
manifestations of TB
Partners in Global Health Education
Click for the
correct answer
How to use this module
Learning outcomes
What is TB?
a) Pericarditis
a
b) Meningitis
b
Epidemiology
Microbiology
Transmission
Section 1 quiz
Natural history
Section 2 quiz
Symptoms and signs
Section 3 quiz
Diagnosis
c) Erythema nodosum
c
Treatment
Prevention and control
Section 4 quiz
Information sources
d) Osteomyelitis
d
e) Phlyctenular conjunctivitis
e
Summative assessment
Question 8: The following are indicated in the
management of miliary TB
Partners in Global Health Education
Click for the
correct answer
How to use this module
Learning outcomes
What is TB?
a)
High protein diet
a
b)
BCG Vaccination
b
c)
Contact tracing
c
d)
Isoniazid prophylaxis for 6-12
months
d
e)
Lumbar puncture
e
Epidemiology
Microbiology
Transmission
Section 1 quiz
Natural history
Section 2 quiz
Symptoms and signs
Section 3 quiz
Diagnosis
Treatment
Prevention and control
Section 4 quiz
Information sources
Summative assessment
Sources of information / bibliography
Partners in Global Health Education
How to use this module
You can copy and paste the links below into your browser to access
the resources:
Learning outcomes
What is TB?
Epidemiology
Microbiology
Transmission
•
•
Section 1 quiz
Natural history
Section 2 quiz
Symptoms and signs
Section 3 quiz
Diagnosis
Treatment
Prevention and control
Section 4 quiz
Information sources
Summative assessment
•
•
•
•
•
Maartens G, Wilkinson RJ. Tuberculosis. The Lancet 2007; 370:203043
Diagnostic atlas of intra-thoracic tuberculosis in children; A guide for
Low Income Countries. Dr. Robert Gie, International Union against
Tuberculosis and Lung Disease (IUATLD) 2003. Available at:
http://www.iuatld.org
The Division for Tuberculosis Elimination, Centre for Disease Control
(CDC), Atlanta, USA http://www.cdc.gov/nchstp/tb/faqs/qa.htm
Stop TB Partnership; http://www.stoptb.org/
WHO – several information resources available at
http://www.who.int/tb/en/
Treatment guidelines: http://www.Nice.ac.uk
TB in the UK: http://www.Hpa.org.uk
Partners in Global Health Education
How to use this module
Summative assessment
Learning outcomes
What is TB?
Epidemiology
Microbiology
Transmission
Section 1 quiz
Natural history
Section 2 quiz
Symptoms and signs
Section 3 quiz
Diagnosis
Treatment
Prevention and control
Section 4 quiz
Information sources
Summative assessment
• Well done! We hope that you enjoyed
completing this module.
• Now try the summative assessment
(available from
http://www.medicine.swansea.ac.uk/inthealth.html)
• … and good luck!