B1.1.2 Infectious diseases/body's defenses

Microbes that cause infectious diseases are called Pathogens.

Bacteria and viruses may reproduce raidly and produce toxins that make us feel ill. Viruses damage the cells in which they produce.

The body has many different ways of protecting ourselves from these pathogens.

White blood cells can help to defend against pathogens by:

• Ingesting pathogens
• producing antibodies, which destroy particular bacteria or viruses
• producing antitoxins, which counteract the toxins released by the pathogens.

The immune system produces antibodies, that kill a particular pathogen. This makes us immune to that pathogen.

Vaccines containing dead or inactive pathogens are given to start the production of antibodies.

Semmelweis recognised the importance of hand-washing to prevent the spread of diseases.

He reduced the number of deaths from infectious diseases in his hospital.

Uncontaminated cultures of microorganisms are required for seeing the effect of disinfectants and antibiotics for this:

1. Petri dishes and equipment must be sterilised to kill microorganisms.

2. Innoculating hoops used to transfer microorganisms must be passed through a flame to kill unwanted bacteria.

3.The lid of a Petri dish should be secured with tape to prevent contamination from the air.

In labs cultures should be incubated at a maximum of 25'c which reduces the risk of harmful pathogens growing.

 In industrial conditions higher temperatures can produce more rapid growth.