Infectious Diseases - Medicines

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  • Infectious Diseases: Medicines
  • Chemicals vs pathogens
  • Antibiotic resistance
  • Developing medicines
  • Different types of medicines
  • Quiz

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Chemicals v pathogens

Ever since people realised that infectious diseases are caused by organisms such as bacteria, fungi and viruses, they have been trying to kill off the pathogens. Many different types of chemicals have been tried, some with more success than others. Chemicals which can destroy microorganisms such as bacteria, fungi or viruses and stop them infecting other people are known as antimicrobials. Successful antimicrobials include:


Chemicals such as bleach which can destroy bacteria, fungi and viruses. They are usually very toxic (poisonous). This means they can be used on surfaces and objects but not on the skin or inside the body. They can prevent the spread of infection from food preparation surfaces, toilets etc.

Disinfectants keep surfaces clean.

Disinfectants keep surfaces clean
© iStock


Chemicals which can be used to destroy microorganisms on the surface of the skin but are too toxic to be taken into the body. They can prevent the spread of infection into the body from cuts and sores on the skin. Antiseptic hand washes can prevent the spread of infection from one person to another through skin contact.

Antiseptics keep your skin clean and help prevent the spread of infection.

Antiseptics keep your skin clean and help prevent the spread of infection
© iStock


Chemicals which can be used to destroy bacteria and fungi inside the body. Antibacterials such as penicillin are used to treat bacterial infections. Antifungals are used to treat fungal infections.

In the past hundreds of thousands of people died in the UK every year from infectious diseases. This included many young children. Antibiotics have saved millions of lives around the world since they were first discovered. Some commonly used antibiotics include penicillin, amoxicillin, chloramphenicol, erythromycin and vancomycin.

Antibiotics do not destroy viruses. Because viruses only reproduce inside other cells, it is very difficult to develop drugs that kill viruses without also damaging the body's tissues.

Antibiotics, and other antimicrobials, can be tested to find out how well they work to destroy bacteria. Discs of filter paper are impregnated with the antimicrobial and are placed on the surface of a petri dish containing agar pre-impregnated with bacteria. When the bacteria grow, the effectiveness of the antimicrobial can be seen.

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Testing antimicrobials

Medicine that acts against bacterial infections. Penicillin is an example of an antibiotic.
Protein that is produced by lymphocytes (white blood cells) and that attaches to a specific antigen.
Molecule on the surface of a pathogen that identifies it as a foreign invader to the immune system.
Single-celled organism. Has a cell wall, cell membrane, cytoplasm. Its DNA is loosely-coiled in the cytoplasm and there is no distinct nucleus.
The use of biological organisms or enzymes to create, break down or transform a material
To cut apart, or separate, tissue especially for anatomical study.
Exponential growth
If something is growing exponentially the larger the quantity gets, the faster it grows
Micro-organism that can grow in long tubes called hyphae or as single cells. Fungi have a nucleus, cytoplasm and a cell wall.
Herd immunity
If a high percentage of a population is immune to a disease the disease cannot be passed on because it cannot find new hosts.
Infection caused by the human immunodeficiency virus (HIV). It attacks and destroys the immune system.
Hybridoma cells are formed by fusing a specific antibody-producing cell with a type of cancer cell that grows well in tissue culture
Immune system
The body's natural defence mechanism against infectious diseases.
A process which gives immune resistance to a particular disease. The human or animal is exposed to a harmless antigen in order to raise antibodies and provide an immune memory.
A type of white blood cell that make antibodies to fight off infections.
A type of white blood cell that consumes dead pathogens that have been killed by antibodies.
Organism that feeds off another living host and causes it some damage. An example of a parasite is a tapeworm that lives in the digestive system of a host organism.
A micro-organism that causes disease.
Phagocytes are the white blood cells that protect the body by ingesting harmful foreign particles, bacteria, and dead or dying cells.
A polymer made up of amino acids joined by peptide bonds. The amino acids present and the order in which they occur vary from one protein to another.
Protozoa are one-celled animals
A spore is a reproductive structure that is adapted for dispersal and surviving for extended periods of time in unfavourable conditions.
A poisonous or toxic substance - produced by pathogens.
A small amount of dead or weakened pathogen is introduced into the body. It prepares the immune system to prevent future infections with the live pathogen.
Medicine that contains a dead or weakened pathogen. It stimulates the immune system so that the vaccinated person has an immunity against that particular disease.
The smallest of living organisms. Viruses are made up of a ball of protein that contains a small amount of the virus DNA. They can only reproduce after they have infected a host cell.
How well the drug works