Tuberculosis Research

Tuberculosis

TuberculosisLearning Objectives Explain how bacterial and viral infectious diseases have asequence of symptoms that may result in death, includingthe diseases caused by Mycobacterium tuberculosis (TB)

TB is an infectious disease that can affect any part of the body although it is usually found in the lungs.Mycobacterium tuberculosisBetween humansDroplet infectionMycobacterium bovisBetween humans and cattleMilk (unpasteurised)& droplet infectionWhat is TB?

Human TB in sputum

1/3 of the World have this diseaseClose to 2 million deaths per year30% of Deaths in Africa13% Aids Victims will die from TBThere are 2 things wrong or not useful in this information. Can you spot them?

Estimated tuberculosis incidence (2010) Data are from a WHO report.4 The 22 countries with the highest burden of tuberculosiswhich account for 80% cases worldwideare labelled.Chest X-ray of a person with advanced tuberculosis. Infection in both lungs is marked by white arrow-heads, and the formation of a cavity is marked by black arrows.

SymptomsFever Night-time sweating Loss of weight Persistent cough Constant tiredness Loss of appetite Coughing up blood

How is it caught? aerosol infection.22% of those in close or prolonged contact with a person carrying the disease become infected. Is associated with AIDS people with immune-suppression caught it more easily.Course of Infection1. Primary infection.Can last for several months and give no symptoms.The person infected deals with the infection by their macrophages engulfing the bacteria that have invaded the lung.However masses of tissue forms that has dead bacteria and macrophages in the centre.These tissues are called tubercules.After 3-8 weeks the infection is controlled and the lung heals.Most primary infections happen in childhood.

White spots are tubercules. These are in rabbits lungs.Second phase.Active TB.Happens when a previous infection is no longer controlled or if the body is overwhelmed by a high dose of bacteria.

What things might trigger a reactivation of TB?

Bacteria multiply rapidly and break down tissue in the lungs causing spaces where alveoli should be.

How will this affect gas exchange?

The bacteria target T-cells and therefore reduce the production of antibodies.

Which T-cells will help antibody production?

Eventually TB causes death.How?

VaccinationWestern Countries - The Bacillus Calmette-Guerin (BCG) vaccineAttenuated version of M. bovis What does attentuated mean?

Drugs must be taken for 6-9 months

Drug-resistant strainsExplain this graph

Discuss how the theory of an evolutionary race betweenpathogens and their hosts is supported by the evasionmechanisms as shown by Human Immunodeficiency Virus(HIV) and Mycobacterium tuberculosis (TB).How TB evades the Immune system.Bacteria have a thick waxy outer layer which protects them from attack by macrophage enzymes. Lie dormant in the tubercules until the person has a weakened immune system.

What selection mechanism is happening here?TB can disable two of the mechanisms a macrophage uses against bacteria. First it disrupts the production of cytokines. Second it stops the apoptosis of the macrophage which normally will happen after invasion.