Download TB File

Specification- topic 6
11 Explain how bacterial and viral
infectious diseases have a sequence of
symptoms that may result in death,
including the diseases caused by
Mycobacterium tuberculosis (TB) and
Human Immunodeficiency Virus (HIV).
WHO targets for TB
http://www.who.int/tb/global-tb-reportinfographic.pdf?ua=1
Tuberculosis (cause)
Caused by bacteria
Mycobacterium tuberculosis
(Mycobacterium bovis)
Tuberculosis (global importance)
Annual incidence 9 million worldwide
Annual incidence 7600 in UK
Annual mortality 2 million
1/3 of World’s population infected
Infection vs Symptoms
Infection = The invasion and
multiplication of microorganisms such as
bacteria, viruses, and parasites that are not
normally present within the body.
Symptom = Any subjective evidence of
disease. In contrast, a sign is objective.
Blood coming out a nostril is a sign; it is
apparent to the patient and doctor, etc.
Tuberculosis (symptoms)
Only infects 30% of close associates to sufferer
Only 5-10% of infected people develop symptoms
Racking cough
Coughing blood
Shortness of breath
Fever
Weight loss
Tuberculosis (transmission)
Spread by airborne droplets
and via unpasteurised milk
Tuberculosis (people at risk)
People who live in overcrowded conditions most at risk
(airborne droplets)
Low immunity
Malnutrition
HIV +
Tuberculosis (decline in UK)
Tuberculosis
bacterium
identified
BCG
vaccination
began
Chemotherapy
began
Tuberculosis (causes of decline)
Better housing
Better diet
Antibiotic
Streptomycin 1940s
Cattle tested for TB
Pasteurisation
Vaccination with BCG
derived from M. bovis
Tuberculosis (causes of decline)
Vaccination with BCG derived from M. bovis
All UK children immunised from 1950s to 2005
Initially a skin test «Heaf test»
If no reaction, then immunised
Today only high risk children immunised –
Living in a high risk area
Parents or grandparents from a high risk country
Immigrants from a high risk country
Tuberculosis (causes of increase)
Recent resurgence since mid-1980s
Linked to drug-resistant forms
Linked to AIDS
Switzerland
Incidence per 100,000 of the population
(Red line = TB + HIV)
http://www.dailymail.co.uk
/news/article36016/Doctors-fightmajor-TB-outbreakschool.html
TB Primary infection
Infection starts when bacteria in droplets of
mucus or saliva are inhaled
Bacteria implants in the lungs
Presence of bacteria triggers an immune
response
Inflammatory response
What is an inflammatory response?
Primary Infection
A granuloma forms, a mass of infected tissue
and macrophages walled off with fibrous tissue
to protect the lungs
Bacteria and immune cells in the centre of
granuloma die due to lack of oxygen, this is now
called a tubercule- Q 6.37
Heals after several weeks
90% of cases occur in children who have no
symptoms
Evasion of immune system
The bacterium can survive in macrophages
and evade the immune system - lie
dormant. Why?
They have a very thick, waxy cell wall which
protects them from the enzymes in the
macrophages.
The waxy cell wall contains peptidoglycan,
but is over 60% lipids this affects
permeability.
T cells are suppressed so fewer or no
antibodies can be produced by B cells.
Active TB
Dormant TB becomes active due to suppressed
immune system.
Who might have a compromised immune
system?
Very young, old, other infections or diseases (HIV
positive)
TB is an opportunistic infection:
takes opportunity when one’s immune system is
weak.
Active TB
What happens during respiratory pulmonary
tuberculosis?
Bacteria can multiply and cause cavities to form in lung
tissue.
Untreated it will lead to death.
Q 6.33
What are the symptoms?
Coughing or coughing up blood
Trouble breathing
Lethargy
Fever
Weight loss or loss of appetite
Fever
Fever-causing substances released from neutrophils
and macrophages
Sets the hypothalamus to a higher temperature
How does the body increase its temperature?
Increases immune response and phagocytosis
Decreases pathogen reproduction
Eg TB bacterium stops reproducing at 42oC
However a fever of 42oC+ is life threatening
Glandular TB
What is glandular TB?
Secondary infection of lymph glands, bones
and CNS
What is a common symtom?
Swollen lymph nodes in neck or armpits
Tuberculosis (diagnosis)
Patient history
Skin tests – tuberculin injected under the skin
Skin test can give false negatives (latent infection)
Skin test can give false positives (BCG vaccination)
Blood test
Analysed for T-cell specific to antigens on M. tuberculosis
Chest X-rays
Tuberculosis (treatment)
Identify M. tuberculosis in sputum
microscopic analysis
Contact tracing
Possible isolation
Multiple antibiotic therapy
Improved lifestyle
Robert Koch
1843 – 1910
Discovered
M. tuberculosis
Tuberculosis (problems)
Slow growing
Intracellular parasites
Metabolically inactive
People tend to stop taking
drugs so the bacteria are
becoming resistant
MDR-TB a problem
Supervision needed
HIV pandemic has been
followed by TB pandemic
Drug resistant TB cases
https://extranet.who.int/sree/Reports?op=vs&path=/WHO_HQ_Report
s/G2/PROD/EXT/DRTB_map&propWidth=1260&propHeight=872