The microorganisms which cause diseases are called PATHOGENS.
Once BACTERIA and VIRUSES get inside your body they REPRODUCE RAPIDLY.

How are pathogens spread?

Defense mechanisms

Painkillers: help to relieve the symptoms of an infectious disease but do not kill the pathogens.
Antibiotics: only work on bacteria by destroying their cell walls (viruses live inside our cells).

Mutation: MRSA - 1000 deaths a year UK
When bacteria reproduce their DNA is made very quickly causing mistakes and mutations that can give them resistance to a certain antibiotic.
The immune system can deal with resistant and non resistant bacteria alike.

Steps to reducing this problem.

Epidemic:
More cases than would normally be expected.
Pandemic:
Much larger/worldwide scale e.g. bird flu.

White blood cells:
Phagocytes: lobed nucleus, ingest/engulf and destroy pathogens.
Lymphocytes: large nucleus, produces antibodies and antitoxins.

Antigens are the chemical on the surface of a pathogen that stimulates an immune response.
Antibodies attach to these ready for the phagocytes to destroy.
Antitoxins counteract the toxins released by the pathogens.

VACCINATIONS = ACQUIRED IMMUNITY.
Made from a dead or inactive form of the disease causing pathogen OR the antigens.
This triggers your natural immune response.

Louis Pasteur, 1850s: It was thought that life originated from non-living forms of matter - SPONTANEOUS GENERATION.
'Swan-necked flask' with sterile broth, bacteria was trapped in the bend, neck was broken and bacteria got in.

Alexander Fleming accidentally discovered a fungus (penicillium) growing on an old bacterial plate which had killed all the bacteria around it.
The first antibiotic - penicillin.

Agar Plates and Aseptic Techniques:
Uncontaminated cultures of microorganisms are required for investigating the action of disinfectants and antibiotics.
Wash hands & swab bench with disinfectant.
Heat inoculating loop & neck of bottle to sterilize.
Open lid of agar plate slightly & for a short amount of time - reduce air contamination.