TBsummarised

TB

Caused by Mycobacterium tuberculosis, a bacterium.

The bacteria are prokaryotic cells Every year 1.6 million people die from

this disease.

Prokaryotic Cell StructureAs you can see, the structure is very different from plant and animal cells that we have already learnt about.

Capsule is a layer of mucilage which may unite bacteria into colonies.

Pili are protein rods concerned with cell-cell attachment. The sex pilus is involved in DNA transfer

Plasma membrane is a typical phospholipid bilayer.

Plasmids are small pieces of circular DNA which replicate independently of the main genome.

Cell wall has a rigid framework of murein, a polysaccharide cross-linked by peptide chains.

Genetic material is composed of a circle of double-stranded DNA which is not enclosed within a nucleus.

Ribosomes smaller than those in eukaryotes and not supported by an endoplasmic reticulum.

Food stores are typically lipid droplets glycogen granules.

Flagellum is responsible for motility of many bacteria.

Development of TB

Spread by a person who has TB coughing or sneezing droplets of mucus containing the bacterium in the air.

Droplets are breathed in by another person and the Mycobacterium infects the lungs.

Also can be caught by drinking unpasteurised milk from cows infected with Mycobacterium bovis.

TB infected sputum

TB infection

Usually infects lungs, but can infect almost any organ in the body.

Symptoms – fever, weight loss, persistent cough and very tired. This is the primary infection.

Healthy immune system – disease may not spread any further.

If the disease does develop, patient will cough up blood-stained sputum due to damaged lung tissue. Chest pain and night sweats will also be present.

Diagnosis

Chest X-ray; infected area looks cloudy.

Sputum sample – examined in a laboratory to see if TB bacteria is present.

TB can spread to other organs such as the heart, bones, pancreas, thyroid and skeletal muscles

TB links

Increased likelihood of developing TB if: Live in damp, overcrowded conditions Abuse alcohol / drugs Infected with HIV Suffering from other medical conditions

that make the body less able to resist disease (e.g. diabetics)

Treatment of TB

Like all bacterial infections TB can be treated successfully using antibiotics. Isoniazid is the drug of choice.

The problem: The drugs need to be taken over six to nine

months to be effective. Initially the patient feels ill so takes the medication and the most susceptible strains of Mycobacterium are destroyed. As the patient feels better they stop taking the medication, however the more resistant Mycobacterium strains are still present in the body ; these multiply and spread to others. These bacteria are likely to be the resistant ones.

Treatment – the solution

To try to stop resistance developing, TB patients are usually given a cocktail of three or four different drugs – hopefully at least one of these will be effective.

A scheme called DOTS (Direct Observation Therapy) has been developed. Here patients are watched while they take their medication, this ensures they complete the course of treatment. DOTS also enable the patients health to be monitored.

Vaccination – BCG (Bacille-Calmet-Guerin) vaccine, This is an attenuated vaccine – it contains a live but weakened strain of Mycobacterium bovis.