3- Infection and response Flashcards
What type of pathogen is measles?
Virus
What are the symptoms of measles?
Fever and a red skin rash
How is measles spread?
Inhalation of droplets from coughs and sneezes - very infectious
How is measles treated?
Treatment: no treatment - infected people have to be isolated
How is measles prevented?
Prevention: vaccine for young children
Other facts about measles
Can cause blindness and brain damage and may be fatal if complications arise
What type of pathogen is HIV/AIDS?
Virus
Symptoms of HIV/AIDS
Initially fever and only mild flu-like symptoms
Late stage of HIV attacks immune system cells over many years so no longer able to deal with infections or cancers (called AIDS)
How is HIV/AIDS spread?
Sexual contact, placental transfer, and exchange of body fluids e.g. blood when drug users share needles, or from mother to child through her breast milk
How is HIV/AIDS treated?
Treatment: Antiretroviral drugs (expensive), no cure
How is HIV/AIDS prevented?
Prevention: Condoms, no sharing of needles for transfusions, HIV mums bottle feed. (No vaccine - an mRNA one on the horizon)
Other facts about HIV/AIDS
Drugs not available to those that need most in Sub Saharan Africa so life expectancy low
What type of pathogen is Salmonella?
Bacterial
Symptoms of Salmonella
- Symptoms develop within 8-72hrs of eating infected food
- Symptoms include fever, abdominal cramps, vomiting and diarrhoea
- For many people Salmonella infections are unpleasant but don’t last many days- however, can be fatal for young children and the elderly due to dehydration
How is Salmonella spread?
Eating infected food
Found in the guts of many different animals - in raw meat, poultry, eggs and egg products. Common causes of infection include eating undercooked food and food prepared in unhygienic conditions
Treatment for Salmonella
Treatment: Antibiotics not usually given, usually self-resolves
Prevention for Salmonella
Prevention: keeping raw meat away from food eaten uncooked, washing hands and surfaces, cooking food thoroughly
Other facts about salmonella
In countries where there is malnutrition, Salmonella is more serious
What type of pathogen is gonorrhoea?
Bacterial
Symptoms of gonorrhoea
Symptoms in early stages include a thick yellow or green discharge from the vagina or penis and pain on urinating.
It then becomes relatively symptomless - some have no symptoms at all.
Untreated gonorrhoea can cause long-term pelvic pain, infertility and ectopic pregnancies
Babies born to infected mothers may have severe eye infections and even become blind
How is gonorrhoea spread?
Unprotected sexual contact with an infected person
Treatment for gonorrhoea
Treatment: antibiotics (Penicillin) - was easily treated with penicillin until resistant strains appeared
Prevention for gonorrhoea
Prevention: use of a barrier method of contraception
What type of pathogen is malaria?
Protist
Symptoms of malaria
Recurrent episodes of fever and shaking - can be fatal
Malaria affects the liver and damages red blood cells
How is malaria spread?
Use mosquitoes as vectors of the disease
Treatment for malaria
Treatment: If diagnosed quickly, it can be treated using anti-malarial drugs
Prevention for malaria
Prevention: Preventing mosquitoes from breeding and using mosquito nets to avoid being bitten, using insecticides to kill mosquitoes in homes and offices, taking antimalarial drugs
Other facts about malaria
The drugs required to treat malaria are not always in the countries most affected by malaria. Globally several hundred million cases of malaria occur each year
What type of pathogen is Tobacco Mosaic Virus (TMV)?
Virus
Symptoms of Tobacco Mosaic Virus (TMV)
Gives a distinctive ‘mosaic’ pattern of discolouration on the leaves. Loss of chlorophyll leads to loss of photosynthesis and death of plant
How is Tobacco Mosaic Virus (TMV) spread?
By direct contact between diseased plants and healthy plants, and insects can act as vectors
How can Tobacco Mosaic Virus (TMV) be prevented?
Prevention: Good field hygiene and good pest control, as well as growing TMV-resistant strains of crop plants, destroy and burn infected plants
How can Tobacco Mosaic Virus (TMV) be treated?
Treatment: No treatment
Other facts about Tobacco Mosaic Virus (TMV)
Affects around 150 species of plants including tomatoes and tobacco plants
The virus can remain infectious in the soil for about 50 years
What type of pathogen is rose black spot?
Fungus
What are the symptoms of rose black spot?
Purple or black spots develop on leaves, which often turn yellow and drop early
Affects the growth of the plant as photosynthesis is reduced
How is rose black spot spread?
In the environment by water or wind - Airborne
Rose black spot prevention
Prevention: Removing and burning affected leaves and plants
Rose black spot treatment
Treatment: using fungicides and/or removing and destroying the affected leaves
Other facts about rose black spot
Horticulturists have developed types of roses that are relatively resistant to black spot
What are pathogens?
Pathogens are microorganisms that cause infectious disease. Pathogens may be viruses, bacteria, protists or fungi. They may infect plants or animals and can be spread by direct contact, by water or by air
How do bacteria make us feel ill?
They produce toxins that damage tissues
Why is it difficult to produce anti-viral drugs?
It is difficult to develop drugs similar to antibiotics for viruses because viruses make us ill by reproducing inside our cells and killing them. Therefore killing the virus will also kill our own cells and tissues
What are antibiotics used for?
Used to kill bacteria in the body
Problems with antibiotics
- overuse of antibiotics for non-bacterial infections is leading to the emergence of resistant strains of bacteria
- The most cited example is MRSA
- This is a problem as it may mean that infections e.g. which happen after operations cannot be treated and morality is increasing
What are examples of non-specific defences?
Skin, nose, trachea and bronchi and stomach
How does skin defend the body?
- impermeable barrier to prevent pathogens entering the blood
- oil on surface of the skin repels pathogens
- if you bleed platelets form a clot that dries into a scab
How does the nose defend the body?
makes sticky mucus which traps pathogens
How do the trachea and bronchi defend the body?
- makes sticky mucus which traps pathogens
- the cilia of the epithelial cells lining the airways send this mucus up to back of throat to be swallowed
How does stomach defend the body?
- Stomach makes hydrochloric acid which kills pathogens in mucus and food you swallow
Key points on specific defences
- Pathogens have specific shaped proteins on their cell surface membranes which identify them. These proteins are called antigens
- Phagocytes are a type of white blood cell that engulf, digest and therefore destroy pathogens that make it into the blood
- Lymphocytes are a type of white blood cell that makes antibodies each with a unique shape to fit a specific antigen
- Lymphocytes also make antitoxins which bind to toxins made by bacteria and neutralise them
What are the four types of pathogens?
- Viruses
- Bacteria
- Fungi
- Protists
How do viruses make us ill?
Viruses reproduce inside our cells, killing the host cell, and destroying tissues
What are the methods of transmission for communicable diseases?
- Water
- Air
- Vectors
- Direct contact
- Sexual contact
- Placental transfer
Give an example of a communicable disease that is spread through water
cholera
Give an example of a communicable disease that is spread through air
measles
Give an example of a communicable disease that is spread through vectors
malaria (protist)
Give an example of a communicable disease that is spread through direct contact
tobacco mosaic virus
Give an example of a communicable disease that is spread through sexual contact
gonorrhoea
Give an example of a communicable disease that is spread through placental transfer
HIV
What are antibiotics?
Drugs which are used to kill bacteria only
What was the first antibiotic discovered?
Penicillin
Who discovered penicillin and when?
Alexander Fleming in 1928
How does penicillin work?
Penicillin works by preventing bacteria from forming cell walls
This causes the bacteria to burst open or rupture
What is a problem with antibiotics?
Overuse of antibiotics for non-bacterial infections is leading to the emergence of resistant strains of bacteria
The most cited example is MRSA
This is a problem as it may mean that infections (e.g. which happen after operations) cannot be treated and mortality is increasing
Definition of an antibiotic
A drug that kills bacteria in the body
Definition of a painkiller
A drug that relieves the symptoms of a disease
How does vaccination work?
When your body is exposed to a pathogen for the first time you become ill. This is because your lymphocytes do not produce a high enough concentration of antibodies quickly enough
Key points on antibiotics
- many types of antibiotics and each kill bacteria in the body therefore treating bacterial infections
- it is important that specific bacteria should be treated by specific antibodies
Why can antibiotics not kill viruses?
Viruses live inside cells.
It is difficult to develop drugs similar to antibiotics for viruses because viruses make us ill by reproducing inside our cells and killing them. Therefore killing the virus will also kill our own cells and tissues
Antibiotic resistance by natural selection
- Bacteria show variation because of mutations which produce new strains
- Antibiotics kill non-resistant bacteria
- Resistance bacteria to the antibiotics survive and reproduce
- The population of resistant bacteria increase because people are not immune to it and there is no effective treatment
What was digitalis used for?
Strengthening heartbeat
Since when has digitalis been used?
Since 1800s
What is the modern equivalent of digitalis?
Digoxin
Where does digitalis come from?
The foxglove plant
Where does aspirin come from?
The bark of the willow tree
What has been done to aspirin?
It has been chemically modified to make it more effective
What does aspirin do?
It is a painkiller
Why do we need to test drugs?
- Toxicity (is it toxic/safe? does it have side effects?)
- Efficacy (is it effective? i.e. does it work?)
- Dose (how much is enough?)
What is the drug development timeline?
- Hundreds are drugs are made in a lab
- The drugs are tested on cells, tissues and whole organs in a lab
- The drugs are tested on animals to find out how they affect a whole living organism (reason: toxicity)
- Low doses of the drugs are given to healthy people to check for side effects (reason: toxicity)
- Higher doses of drugs are given to patients with the disease to see if they work (reason: efficacy)
- Bigger trials in humans take place to find the optimum dosage (reason: dose)
- Safety is monitored long-term once doctors are allowed to prescribe it
What stages in the drug development timeline are in the pre-clinical trials stage?
- Hundred of drugs are made in a lab
- The drugs are tested on cells, tissues and whole organs in a lab
- The drugs are tested on animals to find out how they affect a whole living organism
What stages in the drug development timeline are in the clinical trials stage?
- Low doses of the drugs are given to healthy people to check for side effects
- Higher doses of drugs are given to patients with the disease to see if they work
- Bigger trials in humans take place to find the optimum dosage
- Safety is monitored long-term once doctors are allowed to prescribe it
What is a double blind trial?
2 groups, 1 given drug + 1 given placebo. Doctor and patients don’t know which is given what to avoid bias
What is a control group?
A group in the trial given the placebo - used as a comparison to see the effect of the drug
What is a placebo?
A sugar pill (or similar) that doesn’t contain the drug itself
Uses of monoclonal antibodies
- Diagnosis e.g. pregnancy tests
- Detection of levels of hormones, chemicals and pathogens in blood
- Locate and identify specific molecules in a cell or tissue
What happens in the reaction zone of a pregnancy test?
The monoclonal antibody 1 with enzyme binds to the MCG (if present) - moves up the strip
What happens in the test zone of a pregnancy test?
MAB 2 binds to the HCG attached to MAB 1 - enzyme reacts with dye substrate -> colour change
What happens in the control zone of a pregnancy test?
MAB 3 binds to MAB 1 to show MAB 1 has moved - colour change due to enzyme 1 substrate
Uses of Monoclonal Antibodies: Detection of levels of hormones, chemicals and pathogens in blood
Since monoclonal antibodies are designed to be complementary to a specific antigen, they can be used to detect the presence and amount of pathogens in the blood
Can also be used to detect hormones or chemicals with these acting as antigens (things the monoclonal antibody can bind to)
Uses of Monoclonal Antibodies: Locate and identify specific molecules in a cell or tissue
e.g. by binding a MAB to a fluorescent dye, if it then binds to the specific antigen on a pathogen, then dye will light up showing its presence
Uses of Monoclonal Antibodies: Treat diseases such as cancer
The monoclonal antibody can be bound to a radioactive substance, toxic drug or a chemical which stops cells dividing and growing. It delivers this substance to the cancer cells without harming other cell sin the body
What is an antibody?
An antibody is a protein produced by a type of white blood cell called a lymphocyte. It has a complementary shape to a specific type of antigen
What is an antigen?
An antigen is a protein displayed on the cell surface membrane of a cell which identifies that cell to the immune system
What are monoclonal antibodies?
- Proteins that are produced from a single clone of cells
- They are specific to one binding site on one protein antigen and so target a specific chemical or cell in the body
How are monoclonal antibodies produced?
- Inject a mouse with the antigen you want to make antibodies for
- Remove lymphocytes that produce the antibody from the mouse
- Fuse a lymphocyte with a tumour cell to form a hybridoma cell
- Allow these hybridoma cells to multiply by mitosis to make millions of clones that produce the specific antibody
- Extract and purify the monoclonal antibody
Plant deficiency diseases: Lack of magnesium ions
- Magnesium ions are needed to make chlorophyll
- Without magnesium ions there is less chlorophyll so lose green and go yellow
- This is called chlorosis
- They also are no longer able to photosynthesise
- Therefore less glucose produced
Plant deficiency diseases: Lack of nitrates
- Nitrates are needed for protein synthesis
- Without the ability to make proteins, plants cannot grow
- Nitrate deficiency which leads to stunted growth
What symptoms might plants show if they are diseased?
- dropping of leaves
- malformed leaves
- insects - aphids
- growths
- decay / rotting
- spots + discolouration
- stunted growth
Plant Disease: Aphids
As well as microbial pathogens, insects can infest a plant. Aphids are a common example of these seen in UK gardens and greenhouses. In particular, they infest roses and tomatoes. They are found in large numbers on new shoots, from which they suck sap. This reduces that growth rate of plants and can eventually kill them
What is a physical defence?
A response to resist invasion of microorganisms
What are examples of physical defences?
- Cellulose cell walls
- Tough waxy cuticule on leaves
- Layers of dead cells around stems (bark on trees) which fall off
What are chemical defences?
Releases chemicals to deter a herbivore or kill microorganisms
Examples of chemical defences
- Antibacterial chemicals
- Poisons to deter herbivores
What are mechanical adaptations?
A structure on the plant that will deter a predator
How are plant diseases identified?
- using a gardening manual or website
- taking infected plants to a laboratory
- using testing kits with monoclonal antibodies
Why can’t antibiotics kill viruses?
Antibiotics cannot kill viruses because viruses live inside cells
