Infectious Diseases

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Microbes that cause infectious disease are called pathogens.

Bacteria and Viruses reproduce rapidly inside the body. Bacteria often produce poisons/toxins that make us feel ill. Viruses live inside cells, causing damage; this also makes them harder to kill/treat without harming other cells.

White blood cells have two functions to defecnt against pathogens. Firstly, they produce anti bodies and anti toxins, which attatch to the bacteria or virus cell. Anti toxins counteract the toxins released by pathogens. Specific antibodies kill a particular pathogen. Secondly, they engulf and kill the pathogen.

Vaccinations are the insertion of a dead, or weakened (NOT reduced) pathogen into the body. The immune system then works against this, producing the anti bodies required to defend against the fully functioning pathogen. When the body encounters the real disease, the immune system recognises the pathogen and produces the required anti bodies, reducing the spread and reproduction of the pathogen.

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Antibiotics are  medicines that help to cure bacterial disease by killing infective bacteria inside the body. Antibiotics are not used to treat viruses.

Specific bacteria are are treated with specific antibiotics.

In case of mutation in bacteria, antibiotics may become ineffective against the new strain of pathogens.

Many strains of bacteria, such as MRSA (Methicillin-Resistant Staphylococcus Aureus) have developed resistance to antibiotics. This can come from improper, or overuse of an antibiotic.

The development of antibiotic-resistant strains of baxteria emphasises the need for development of new antibiotics.

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Defence against infectious disease - experiments

Uncontaminated cultures of microorganisms are required for investigating he action of disinfectants and antibiotics.

Petri dishes must be sterilised in order to kill unwanted microbes

Sterile inoculating loops must be used to transfer microbes. This can be achieved by passing them through a flame.

The lid of a petri dish must be sealed with adhesive tape to prevent microbes from the air from entering

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