Infection and response

Created by

Grace Tregidgo

Cards (41)

What is a pathogen?
A microorganism that causes disease
Cause communicable diseases
Both plants and animals can be infected by pathogens
What are the types of pathogen?
bacteria, viruses, fungi, and protists
What is bacteria?
Very small cells which can reproduce rapidly inside your body

Make you feel ill by producing toxins that damage your cells and tissues
What are viruses?
They are not cells, they replicate themselves inside cells and then the cells burst releasing all the new viruses

Cell damage is what makes you feel ill
What are protist ?
single cell eukaryotes

Some are parasites which live on or inside which causes damage

Often transferred by a vector
What is fungi ?
Some are single-celled . Others have a body made up of hyphae

Hyphae can grow and penetrate skin and surface or plants causing disease

Hyphae can produce pores
which spread
How to pathogens spread ?
Water- drinking or bathing in dirty water
Air- carried in air then breathed in
Direct contact- picked up my touching contaminated surfaces
What are 3 viral diseases?
Measles, HIV, tobacco mosaic virus (TMV)
What is measles?
It's a viral disease and spread by droplets

Develop skin rash and signs of fever

Can lead to pneumonia or inflammation in the brain (encephalitis)

Most people are vaccinated against them
What is HIV?
A virus spread by sexual contact or by exchanging bodily fluids such as blood

Initially cause flu-like symptoms or no symptoms for 7 years

Controlled with antiretroviral drugs
Virus attacks immune cells which is known as aids
What is tobacco mosaic virus ?
Affects plants

Causes parts of plant to become discoloured

Means that plants can't carry out photosynthesis so it affects growth
What is the fungal disease rose black spot ?
Causes purple or black spots, leaves can turn yellow and drop off

Means less photosynthesis
can happen
Spreads through water or wind

Treat disease by using fungicides and stripping plant of infected disease
What is the protist disease malaria ?
Life cycle takes place in a mosquito

Mosquitos are vectors, they pick it up when feeding on infected animal

They insert protist into blood vessels
Causes repeating episodes of fever
How do you prevent spread of malaria ?
Stopping mosquitos from breeding
Insecticides
Mosquito nets
What are 2 bacterial diseases?
Salmonella and gonorrhoea
What is Samonella?
It is a type of bacteria that causes food poisoning.

Can suffer from fever, stomach
cramps, vomiting and diarrhoea

Get it by eating food contaminated with salmonella bacteria or contaminated by being prepared in unhygienic conditions

In UK poultry are given vaccination to control spread of disease
What is gonorrhea?
sexually transmitted disease

Caused by bacteria

Will get pain when urinate or thick yellow or green discharge from vagina or penis

Originally treated with penicillin but strains of bacteria have now become resistant

To prevent spread treat with antibiotics or barrier methods
How can spread of disease be reduced or prevented?
1) Being hygienic- washing hands before food or after sneezing

2) Destroying vectors- getting rid of organisms that spread disease by
insecticides or destroying habitat

3) Isolating infected individuals

4) Vaccination- less likely to develop infection and pass it on
What is the bodies defence system?
Skin acts as a barrier, also secretes antimicrobial

Hair and mucus in nose trap particles

Trachea and bronchi secrete mucus to trap pathogens, lined with cilia which waft mucus up to back of throat

Stomach produces hydrochloric acid this kills pathogens
How does immune system attack pathogens ?
White blood cells which travel around body looking for microbes to attack
What 3 ways does the immune system attack pathogens ?
Consuming them
Producing antibodies
Producing antitoxins
How do white blood cells consume pathogens ?
white blood cells can engulf foreign cells and digest them (phagocytosis)
How do white blood cells produce antibodies to attack pathogens ?
pathogens have antigens on its surface, when they encounter a white blood cell they produce proteins called antibodies to lock into invading cells so they can be found and destroyed by other white blood cells. Antibodies are produces rapidly and carried around body. If the person gets infected again white blood cells will produce antibodies so person is naturally inmune to that pathogen
How to white blood cells produce antitoxins to attack pathogens ?
they are produced by invading bacteria
How do vaccinations work ?
Vaccinations inject small amounts of dead or inactive pathogens, which carry antigens which cause the body to produce antibodies to attack them.

This means that if live pathogens of this type appear into the body white blood cells can rapidly mass produce antibodies to kill off pathogen
What are the pros of vaccination ?
- helped control lots of communicable diseases that were once common in the UK ( e.g. smallpox no longer occurs at all and polio infections have fallen by 99%)

- epidemics can be prevented if a large percentage of the population is vaccinated - herd vaccination
What are the cons of vaccination?
Vaccines don't always work
You can sometimes have a bad reaction to a vaccine such a swelling or seizure however these are very rare.
What drug relieves symptoms ?
Painkillers- they don't kill pathogens they help reduce symptoms (aspirin)
What drug relieves symptoms ?
Antibiotics- they kill or prevent the growth of the bacteria without killing your own body cells (penicillin)

Antibiotics don't destroy viruses (flu) because viruses reproduce using your body cells which makes it difficult to develop drugs that destroy the virus without damaging body cells
How does bacteria become resistant to antibiotics?
By mutating which may cause them to be resistant to an antibiotic

If you have an infection some bacteria might be resistant so when you treat it only non-resistant strains will be killed. The resistant ones survive and reproduce which can cause serious infection
What is an example of a resistant strain that can cause serious infection ?
MRSA ( meticillin resistant staphylococcus aureus) which causes serious wound infections and is resistant to meticillin
How do you slow down the rate of resistant strain development ?
Doctors must avoid over subscribing antibiotics and you must finish the whole course of antibiotics
How do drugs come from plants ?
Plants produce lots of chemicals to defend themselves against pathogens some of these chemicals can be used in drugs
What medicines were discovered in plants ?
Aspirin used as a painkiller and to lower fever is developed from a chemical found in willow

Digitalis used to treat heart conditions is developed from a chemical found in foxgloves
What drugs were extracted from microorganisms?
Alexandra fleming created penicillin from the mould forming on the bacteria (when he was clearing out the Petri dishes) he found that mould produced a substance that killed off bacteria
How are drugs made these days ?
On a large scale in the pharmaceutical industry-they are synthesised by chemist in labs
How many stages are there in drug testing ?
3
What is the first stage of drug testing ? 
Drugs are tested on human cells and tissues in the lab
What is the second stage of drug testing ?
Testing the drugs on live animals this tests efficacy ( find out about it's toxicity and best dosage )

In British law a new drug must be tested on 2 different live animals
What is the third stage in drug testing ? Part 1
If drug passes on animals it's then tested on human volunteers in a clinical trail

Drug tested on healthy volunteers, to make sure doesn't have harmful side effects. At the start of trail a low dosage is given which is gradually increased.

If results are good drug is then tested on people with illness, optimum dose is found which is most effective and few side effects