Topic 3: Infection and Response Flashcards
What is a disease?
An illness or disorder of the body or mind that leads to poor health
What are communicable diseases?
Caused by pathogens and are transmissible (can be spread between individuals within a population)
What are examples of pathogens?
- Bacteria: reproduce rapidly and can produce toxins which damage tissues of the body
- Viruses: reproduce rapidly within host cells causing cell damage
- Fungi
- Protists
How does transmission, spread of disease, occur?
- Direct Contact
- Water or Air
What methods are used to prevent spread of pathogens?
- Hygienic Food Preparation
- Personal Hygiene
- Waste Disposal
- Sanitation
Are viruses living organisms?
No, as they do not fulfil the 7 life processes as they don’t have nuclei, organelles or cytoplasm and have now way to change environment
How does viruses damage cells?
- Reproduce rapidly by inserting their genetic material into host cells and creating new protein capsules to build new viral particles
- Once many copies have been made, the host cell may burst open releasing the viral particles which can go on to infect other cells
What is measles?
- Highly contagious and a potentially serious viral infectious disease that can be fatal if complications arise
- Often seen in children
What are the symptoms of measles?
- Fever
- Red Skin Rash
- Can cause blindness and brain damage
How is measles spread?
- Inhalation of droplets from coughs and sneezes
- Very infectious
How is measles treated and prevented?
- No Treatment
- Isolation
- Vaccination Programme for young children
What is HIV?
- Human Immunodeficiency Virus
- Lead to AIDS
What are the symptoms of HIV?
- Starts as flu-like illness
- If untreated, can travel to lymph nodes and attack cells of immune system
- Can’t deal with other infections or cancers
How is HIV spread?
- Direct Sexual Contact
- Exchange of Bodily Fluids (needle)
- Mother to child during birth/breast milk
How is HIV treated or prevented?
- No cure
- Antiretroviral Drugs can control disease to slow or halt progression to AIDS
What is TMV?
- Tobacco Mosaic Virus
- Widespread plant pathogen infecting 150 species of plant
What are the symptoms of TMV?
- Distinctive mosaic pattern of discolouration as virus infects chloroplasts
- Stunted Growth due to lack of photosynthesis
- Reduced crop yield
How is TMV spread?
- Plants in direct contact with infected plant
- Stay in soil for about 50 years
- Infected tools
How is TMV treated or prevented?
- No treatment
- Good field hygiene
- Using virus-resistant strains of crop plants
- Cutting off infected sections
What are bacterial pathogens?
Cells that can infect plants and animals causing disease
How does bacteria play a vital role in maintaining health?
- Bacteria on skin act as competitors to harmful pathogens
- Bacteria in large intestine digest substances we can’t in food and provide essential nutrients
How does bacterial pathogens damage body?
Produce toxins that cause damage to cells and tissue directly
What is salmonella?
- Food poisoning spread by bacteria ingested in food or on food prepared in unhygienic conditions
What are the symptoms of salmonella?
- Starts 8-72 hrs of eating infected food
- Secrete toxins that cause fever, abdominal cramps, vomiting and diarrhoea
How is salmonella spread?
- Contaminated food that has not been cooked properly
- Eggs or not cooked egg products (mayonnaise)
How is salmonella treated/prevented?
- Chickens are vaccinated
- Separate cooked and raw meat
- Washing surfaces and hands before and after handling raw meat
What is gonorrhoea?
- Common STD causing 13% of diagnosed STDs
What are the symptoms of gonorrhoea?
- Thick, yellow discharge from vagina or penis
- Pain when urinating
- If left untreated, can cause infertility and pelvic pain
- Babies could get eye infections and be born blind
How is gonorrhoea spread?
Unprotected sexual contact
How is gonorrhoea treated/prevented?
- Barrier methods of contraception
- Antibiotics
- Can be prevented by tracing all sexual partners so individuals can be tested
What fungal disease affect humans?
- Athletes’ Foot
- Spread by contact with surface touched by infected person (shower floors)
What are fungi made up of causing infections?
- Hyphae
- Grow and penetrate surface of plants and animals
- Produce spores which spread infection to other organisms
What is rose black spot?
Fungal disease of plants
What are the symptoms of rose black spot?
- Purple or Black spots on leaves, causing leaves to turn yellow and drop off
- Loss of leaves means less chloroplast for photosynthesis
- Reduction of photosynthesis means less energy to make flowers and stunted growth
How is rose black spot spread?
Spores from fungus are carried in the wind or water
How is rose black spot treated/prevented?
- Fungicide Chemicals
- Leaves removed or burned to prevent spread
- Breeding resistant variation of plant
What are protists?
- Diverse group of eukaryotic and usually unicellular organisms
- Only a small number of protists are pathogenic, but the diseases they cause are often serious
- Often need a vector to transfer from one host to the next
What is malaria?
- Caused by protists from Plasmodium family
- Infect red blood cells
Describe how malaria occurs
- Sexual Reproduction of the malarial parasite from another mosquito
- Female Anopheles Mosquito bites human
- Malarial Parasite infects liver and reproduces asexually
- Enters red blood cell before bursting out into blood
- Mosquito consumes infected blood when feeding
What are the symptoms of malaria?
- Recurrent fever and shaking when protists burst out
- Weaken host (can be fatal)
How is malaria spread?
Mosquito vector
How is malaria treated/prevented?
- Drugs (diagnosed early)
- Protist has become more resistant to drugs
- Controlling mosquito populations with insecticides and preventing breeding
What is a non-specific defence?
First line of defence against an infection
What are examples of the non-specific defence systems?
- Skin
- Nose
- Trachea/Bronchi
- Stomach
What is the role of the immune system?
Prevent infectious organisms from reproducing and to destroy it
What is the main component of the immune system?
White Blood Cells
How do white blood cells help defend against pathogens?
- Phagocytosis
- Production of antibodies
- Production of antitoxins
What is phagocytosis?
- Phagocyte
- Engulf and digest pathogens
- Either non-specific or helped by antibodies which cause agglutination of pathogens (clumping)
- Surround pathogen and release enzyme to digest, break and destroy
How are antibodies produced?
- Lymphocytes
- Y-Shaped Proteins
- Produce an antibody specific to antigen on surface of pathogen
How long does it take for a specific antibody to be produced?
- Few Days
- Enough time for infection to make you feel unwell as number in body increases
How are antitoxins produced?
- Some pathogens (usually bacteria) can produce substances which act as toxins which make you feel unwell
- Lymphocytes can produce antibodies against these substances called antitoxins
- The antitoxins neutralise the effects of the toxin
What is an antigen?
Molecule found on surface of cell
What is an antibody?
Protein made by lymphocytes that is complementary to an antigen and, when attached, clumps them together and signals the cells they are on for destruction
What is an antitoxin?
Protein that neutralises the toxins produced by bacteria
What is the primary purpose of vaccination?
To prevent illness in an individual by providing artificial immunity
What does vaccination involve?
Exposing an individual to the antigens of a pathogen in some form to trigger an immune response which results in the formation of memory cells that can make antibodies against it
How do vaccines affect disease transmission?
Vaccines reduce the likelihood that an infected individual will spread the pathogen they have been vaccinated against to others, as they can destroy it before becoming infectious
What is herd immunity?
The principle where if a large number of the population are vaccinated, it is unlikely that an unvaccinated individual will become infected with the pathogen
Who does herd immunity protect?
Herd immunity protects the vulnerable that may not be able to have the vaccine
What are the three main scenarios with vaccination?
1) No vaccinations and the disease spreads quickly, 2) Some of the population are vaccinated and the disease spreads to less people, 3) Most of the population are vaccinated and this prevents the spread
What is the role of the WHO in vaccination?
To monitor global diseases and track if a disease is endemic, epidemic or pandemic
Why have measles cases increased worldwide despite having a vaccine?
Due to a drop in the vaccination rate globally – there was some controversy over the MMR vaccine in 1998 and the number of vaccinations dropped significantly after this
What happens during vaccination at the cellular level?
Small quantities of dead or inactive forms of a pathogen are introduced into the body to stimulate the white blood cells to produce antibodies
How does the body respond when a vaccinated person encounters the pathogen again?
The white blood cells respond quickly to produce the correct antibodies, preventing infection
What is active immunity?
Immunity that comes from the body creating antibodies to a disease either by exposure to the disease (natural) or by vaccination (artificial)
What is passive immunity?
Immunity that comes from antibodies given to you from another organism, for example in breast milk
What happens with measles vaccination specifically?
Vaccination with a weakened form of the measles virus results in the production of antibodies and memory cells, allowing for quicker production of antibodies when naturally exposed to the virus
What are the three classifications the WHO uses to monitor disease spread?
Endemic, epidemic, and pandemic
How does vaccination affect antibody production upon infection?
When vaccinated and later exposed to the virus naturally, an individual can produce a higher concentration of antibodies much more quickly to destroy it
What are the two types of medication someone can take to treat disease?
Antibiotics and Painkillers
What are antibiotics?
Medicines that help cure bacterial disease by killing infective bacteria inside the body
What was the first antibiotic to be discovered?
Penicillin
Why don’t antibiotics work against viruses?
Viruses reproduce inside cells, making it difficult to develop drugs that kill viruses without damaging the body’s tissues
What do painkillers treat?
Painkillers treat the symptoms of disease (e.g., pain and inflammation) but do not kill pathogens
Why is it important to use specific antibiotics for specific bacteria?
Only certain antibiotics work on certain diseases; doctors prescribe different antibiotics depending on the type of infection
How do antibiotics work?
Antibiotics work by stopping bacteria cellular processes, such as the production of the cell wall, affecting processes usually only in bacteria
When were antibiotics first introduced?
In the 1930s
What is antibiotic resistance?
When bacteria develop the ability to survive treatment with antibiotics that once killed them
How does antibiotic resistance develop?
Through random mutations in bacterial DNA that provide resistance, allowing those bacteria to survive and reproduce when exposed to antibiotics
What is MRSA?
Methicillin-resistant Staphylococcus aureus, a strain of bacteria that has developed resistance to the powerful antibiotic methicillin
Why is MRSA concerning?
It can infect wounds and is difficult to treat without effective antibiotics, making infections more dangerous
Why do bacteria evolve rapidly?
They reproduce quickly and acquire random mutations, some of which confer resistance
How can doctors help prevent antibiotic resistance?
By avoiding overuse of antibiotics and prescribing them only when needed; testing bacteria first to prescribe the correct antibiotic
Why shouldn’t antibiotics be used for viral infections?
Antibiotics only work against bacteria and not viruses; using them for viral infections contributes to antibiotic resistance
Why is it important to finish the entire course of antibiotics?
To ensure all bacteria are killed, preventing any survivors from mutating to resistant strains
How has agriculture contributed to antibiotic resistance?
Through extensive use of antibiotics in farming; controls are now in place to limit their use
What practices help reduce the spread of resistant bacteria in hospitals?
Good hygiene practices such as handwashing, use of hand sanitizers, and isolation of infected patients
Why is the isolation of infected patients important in hospitals?
To prevent the spread of resistant strains, particularly in surgical wards where MRSA can infect wounds
How has the use of antibiotics affected global health?
It has had one of the largest positive impacts on global health
What are two reasons antibiotics should not be prescribed?
For non-serious infections that the immune system can clear up and for viral infections
How was drugs traditionally found?
Extracted from plants and microorganisms
Where does digitalis originate from?
Foxglove
Where does aspirin originate from?
Willow
Where does penicillin originate from?
- Discovered by Alexander Fleming
- Penicillium Mould
- Releasing a chemical killing bacteria around it
What are new drugs tested for?
- Toxicity
- Efficacy
- Dose
How are results tested to ensure accuracy?
Peer-reviewed and published in journals
What are the 3 stages of drug development?
- Preclinical testing
- Whole organism testing
- Clinical Trials
What happens in Preclinical Testing?
- Drug tested on cells in lab
- Computer models may also be used to simulate metabolic pathways taken by drug
- Efficacy and toxicity are tested
What happens in Whole organism testing?
- Drug tested on animals to see effect on whole organism
- Efficacy, toxicity and dosage are tested
What is tested in the 1st stage of Clinical Trials?
- Human Volunteers
- Low dosage before increased
- Make sure it is safe in a body that is working normally
What is tested in the 2nd stage of Clinical Trials?
- Patients with condition
- Split into two groups: Drug and Placebo
- Lowest effective dose is tested
What is a double-blind trial?
Neither doctor nor patient knows which patient is getting placebo or drug preventing bias
What new medications are being looked for?
- Vaccinations to different diseases
- Antibiotics that have a different action on the bacteria, so that bacteria are not resistant to them
- Painkillers with fewer side effects
- Antiviral drugs that don’t damage the body’s tissues
What is meant by testing efficacy?
Does it work?
What is meant by testing toxicity?
Does it have harmful side effects?
What is meant by testing dosage?
What dose is the lowest that can be used and still have an effect?
What are monoclonal antibodies?
Antibodies made by identical immune cells which are clones of parent cell
How are antibodies specific?
Specific to one binding site on one protein antigen so are able to target specific cell in body
How are antibodies produced?
- Stimulate mouse lymphocytes to make a particular antibody by exposing them to antigen
- The lymphocytes are combined with a particular type of tumour cell to make a hybridoma cell (used because they can divide repeatedly)
- Hybridoma cell can divide and produce antibody
- Single hybridoma cells are cloned, creating many divisions, making high quantities of identical cells that produce same antibody
- Large amount of antibody is collected and purified ready for use
Why are MCA’s known as ‘monoclonal’?
Create only one antibody
What are some uses of Monoclonal Antibodies?
- Pregnancy Tests
- Labs to measure levels of hormones
- Locate specific molecules in cell by binding them with dye
- Treat disease like cancer to deliver harmful substance directly to cancer cell
How are monoclonal antibodies used in a pregnancy test?
Monoclonal antibodies are specific to a hormone produced in pregnancy, human chorionic gonadotropin (HCG) and will bind to hormone if present and produce colour change
Describe each stage of the pregnancy test and how HCG influences it.
- Sample Pad is dipped in urine
- HCG antibodies found at reaction zone which are mobile and contain blue dye
- Non-mobile HCG-specific antibodies are found in result window and can display blue dye if binded with mobile HCG
- Non-mobile antibodies which did not bind with mobile HCG move up to control window and if there is blue dye, display
How are monoclonal antibodies used in diagnosis of disease?
MCA Antibodies are specific to antigen on surface of pathogens, blood clots or cancer cells. Contain markers to help doctors find location of them (Prostate Cancer)
How are monoclonal antibodies used in measuring and monitoring?
Detect presence of chemical or pathogen and quantity (Drug Testing or HIV screening)
How are monoclonal antibodies used in treating disease?
- Use of MCA to trigger immune cells to destroy them
- Use of MCA to block receptors to stop growth and division
- Use of MCA to carry toxic or radioactive substances to site of tumour
What are advantages to MCAs?
- Only bind to specific molecules so don’t affect healthy cells
- Treat range of conditions
- Hoped to be a cheap procedure which has been tried and tested
What are disadvantages to MCAs?
- Caused more side effects
- Use of Mice Antibodies had complications
- Currently expensive
- Producing specific MCA is providing to be more difficult than expected
What are aphids?
- Insects which can infest plants
- Have a long sharp mouth pieces that pierce the surface of stem and into phloem so they can feed on sugar filled sap
- Can infest in large numbers and remove large quantities of phloem sap, weakening the plant
- Act as a vector for transfer of diseases
What is the best way to control infestation with aphids?
- Biological Pest Control (using ladybirds, a natural predator of aphid) to feed on them
- Chemical Pesticides
What are the main symptoms of plant diseases and which do they correlate to?
Stunted Growth - RBS, TMV, Mineral Deficiency
Spots on Leaves - RBS
Areas decaying/rotting- RBS, Potato Blight
Visible Pests - Aphids, Caterpillars
Discoloration of Leaves - TMV, Magnesium Deficiency
Growths - Crown Gall Bacteria Infection
Malformed stems and leaves - Aphid infestation
How can plant diseases be identified?
- If in garden, identify by comparing to manuals or online
- Experts can take samples and take them to the lab to undergo DNA analysis to identify pathogen causing problem
- Plant scientist can use MCA testing kits to identify presence of pathogens
What is the use of nitrate minerals in the plant and what are the symptoms of the deficiency?
- Production of amino acids for proteins
- Stunted Growth
- Upper Leaves Pale Green and Lower Leaves Yellow or dead
What is the use of magnesium minerals in the plant and what are the symptoms of the deficiency?
- Synthesis of chlorophyll needed for photosynthesis
- Chlorosis (yellowing leaves) due to less chlorophyll and stunted growth
What is the use of potassium minerals in the plant and what are the symptoms of the deficiency?
- Production of Flowers and Fruit
- Poor growth of flowers and fruit
- Yellow leaves and dead spots
