Unit 20 – Causes and Spread of Infection

Unit 20 – Causes and Spread of Infection

1.1 Identify the differences between bacteria, viruses, fungi and parasites.

Bacteria are microbes with a single cell. There is no nucleus or membrane within bacteria, making its structure simpler than that of other organisms. Instead, the genetic information is contained in a single loop of DNA. Viruses are microscopic organisms consisting of genetic material surrounded by proteins, lipids, or glycoprotein coats. Fungi can be multicellular or single celled organisms. They can be found in almost any habitat but most live on land. A group of fungi called the decomposers grow in the soil and play an important role in the cycling of carbon and other elements. A Parasite is an organism that lives within another organism (the host). It is dependant on the host for its survival as it cannot live independently.

1.2 Identify common illnesses and infections caused by bacteria, viruses, fungi and parasites.

Common illnesses and infections caused by bacteria, viruses, fungi and parasites are:

Bacteria: Salmonella, tuberculosis, MRSA, food poisoning, tonsillitis
Viruses: Common cold, warts, AIDS/HIV
Fungi: Athletes foot, yeast infection, ring worm
Parasites: worms, malaria

1.3 Describe what is meant by 'infection' and 'colonisation'

Infection is the invasion and multiplication of microorganisms that are not normally present within the body. An infection tends to show symptoms and may spread through the whole of the body. Colonisation is when germs are within the body, but do not make the person sick. People who are colonised will have no signs or symptoms and they can feel fine.

1.4 Explain what is meant by 'systematic infection' and 'localised infection'

A systematic infection is an infection that is spread throughout the 'systems' of the body, usually by the bloodstream. This doesn’t mean the infection is more severe than a local infection, it just affects a larger proportion of the body. A...