Task 3; Infectious Diseases Flashcards
Bacteria structure
Bacteria are prokaryotic, unicellular organisms. They don’t have membrane-bound organelles. Their DNA is contained in a single loop known as a nucleoid.
What per cent of bacteria is pathogenic
Not all bacteria cause disease, only 1% of bacteria is identified as pathogenic.
Bacteria can cause disease by:
- Secreting toxins (chemical change)
- Invading cells (physical change)
- Forming bacterial colonies to disrupt cell function
Disease caused by bacteria
include:
- bacteria name
- Disease
- Symptoms
- Treatment
- Vaccine
- prevention
Bacteria – Vibrio cholerae
Disease: cholera (a diarrheal infection)
Symptoms: diarrhoea, vomiting, leg cramps, dehydration
Treatment: Oral Rehydration Solution (ORS) mixture of salt and sugar with of water and drunk in large amounts. Other treatments include intravenous fluid replacement and antibiotics.
Vaccine: Vaxchora
Prevention: drink and use safe water; wash hands often with safe water; cook food well, peel fruits and vegetables and eat food hot; clean up kitchens safely.
Fungi structure
Eukaryotic, non-photosynthetic, heterotrophic organisms with a cell wall. Can be unicellular or multicellular
Fungi can cause disease by:
Fungi secrete digestive enzymes to break down organic matter, which can then be absorbed into the fungus. These substances usually cause disease.
Fungi commonly cause skin infections. These are caused by fungal species which live on the outside layer of skin and break down keratin tissue, producing by-products that cause inflammation and itchiness.
Disease caused by Fungi
include:
- bacteria name
- Disease
- Symptoms
- Treatment
- Vaccine
- prevention
Bacteria name: dermatophytosis
Disease: Tinea
Symptoms: darkening of the skin, peeling, red rashes, or scaly patches, blisters, cracking of the skin
Treatment: The treatment for ringworm is an antifungal medication
Vaccine: Ringvac
Prevention: maintain hygiene, keep skin dry, avoid sharing towels, avoid public swimming pools
Mode of transmission = direct contact, skin to skin contact, surfaces e.g. shower floor
The fungi live outside the layer of the human skin, where they produce chemicals that break down the keratin.
Examples of types of tinea include athlete’s foot, ringworm
Protozoa structure
Protozoa are eukaryotic, unicellular microorganisms that are larger than bacteria, they have internal membranes and have DNA inside the nucleus.
Disease caused by Protozoa
include:
- bacteria name
- Disease
- Symptoms
- Treatment
- Vaccine
- prevention
Protozoa – Plasmodium falciparum
Disease: Malaria (transmitted via Anopheles mosquito)
plasmodium floasts freely int he blood of an infected person, it feeds on haemoglobin in the RBC’s causing them to pop
Symptoms: fever, headache, chills, sweating; gastrointestinal (diarrhea, vomiting, nausea); pain in abdomen and muscles.
Treatment: prescription drugs to kill the parasite; antimalarial drugs are currently being researched and developed.
Vaccine: Mosquirix vaccine (RTS,S)
Prevention: avoid mosquito bites by using insect repellant; use mosquito net.
Protozoa can cause disease by:
Transmission of protozoa that live in a human’s intestine to another human typically occurs through a fecal-oral route (for example, contaminated food or water or person-to-person contact). Protozoa that live in the blood or tissue of humans are transmitted to other humans by an arthropod vector (for example, through the bite of a mosquito)
Disease caused by parasites
include:
- bacteria name
- Disease
- Symptoms
- Treatment
- Vaccine
- prevention
Bovicola ovis
Disease: sheep lice
Symptoms: excessive itching and unwarranted wool loss, damaged wool.
Treatment: shearing fleece to remove lice; pouring preparations containing medicated drugs.
Prevention: stock-proof fences to prevent sheep from straying and catching lice (known as biosecurity); isolating infected sheep; stock introduced in farm should be quarantined and inspected for lice.
Virus Structure
non-cellular entities (non-living), consisting of a single type of nucleic acid (RNA or DNA) encased in a protein coat.
Virus is a very small piece of genetic material encased in a shell called a capsid. Outside of a host, they are called virions with a protein coat (capsid) and inner nucleic acid (DNA or RNA).
Because they contain nucleic acid, they can mutate and evolve. They can also infect bacteria, and these are known as bacteriophages.
Disease caused by a virus
include:
- bacteria name
- Disease
- Symptoms
- Treatment
- Vaccine
- prevention
Virus – Severe Acute Respiratory Syndrome Coronavirus 2
Disease: coronavirus disease (COVID-19)
Symptoms: fever, dry cough, loss of taste and smell
Treatment: rest, drink lots of fluids, and eat nutritious foods; self-isolate and visit the doctor.
Prevention: wear mask, sanitise, cough into elbow, maintain safe distance, stay home if feeling unwell.
Vaccine: Moderna, Resvisir
prevention: social distancing, PPE
Virus can cause disease by:
The virion is the vector stage that is transmitted from host to host. Once a virus penetrates a host’s defences, they shed their capsid and release their nucleic acid into the host for replication by incorporating their DNA or RNA into the host’s genetic material.
Prions structure
They are the smallest known agents of disease comprising solely of protein and no genetic material.
Prions can cause disease by:
Protein’s that have been altered from their normal structure and can then alter other proteins to develop more prions
Prions cause neurodegenerative diseases by promoting abnormal folding of proteins in the host’s central nervous system.
Prion diseases are also called transmissible spongiform encephalopathies (TSEs)
the symptoms usually include spongiform changes associated with loss of neurons (brain damage) and the body’s inability to induce inflammatory responses.
Disease caused by a Prion
include:
- bacteria name
- Disease
- Symptoms
- Treatment
- Vaccine
- prevention
Prions – Bovine spongiform encephalopathy (BSE)
Disease: Mad cow disease (also Variant Creutzfeldt-Jakob disease through contaminated food – zoonic disease)
Symptoms: dementia, problems with coordination, psychosis, unresponsiveness, weight loss and drop in milk (for cattle), behavioural changes, trembling.
Treatment: no cure
Prevention: avoid feeding cattle rendered material from slaughtered animals and to isolate and destroy all infected animals.
Pathogen Adaptations
Adaptations allow pathogens to remain on or in their hosts for longer periods of time or facilitate transmission to other organisms
- Using Vectors to transition between hosts (e.g. mosquitos) are a vector for malaria and ticks for Lyme disease
- Flagella for movement
- Enzymes to break down and penetrates mucous membranes and chemical barriers
- Variations in antigens avoid host recognition e.g. flu
Direct transmission
Contact between reservoir or infected host and new host. This includes sexual contact, skin-to-skin contact or biting in animals. Infection through sneezing, coughing and breathing are also direct as droplets spread.
Indirect transmission
Requires an intermediate between one host and the next. Includes spread of disease through air and dust, in food and water, on surfaces and objects (fomites). Vectors, such as mosquitoes, also spread disease indirectly.
VEHICLE TRANSIMISSON
Spread of pathogens by contaminated food, air or
VECTOR TRANSMISSION
Spread through other organisms. A pathogen in a biological vector undergoes part of its life cycle in the vector (eg. Mosquitos transporting malaria). Mechanical vectors physically transfer the pathogen from one person to another without being infected themselves (e.g. flies)
Portal of entry
Portal of entry is often the same as portal of exit the pathogen must access the type of tissues where it can grow and reproduce.
Susceptible host
The susceptibility of the host relies on many factors, including their genetics, immunity to the pathogen, and overall health. If the host is suffering from malnutrition, for example, their susceptibility will be increased.
what are the three responses to pathogens
Physical barriers
Chemical barriers
Microbiological barriers
Physical barriers
Epithelial cells create a physical barrier that prevents pathogens from entering the organism. These cells line the skin, and the respiratory, gastrointestinal and urogenital tracts. They are joined tightly by specialized membrane proteins to form a continuous barrier against pathogens.
Additionally, adaptations include mucus-secreting membranes that trap invading organisms in mucus and membranes lined with cilia that sweep foreign bodies away (e.g. those that line the airways).
Chemical barriers
External chemicals barriers include lysozyme enzymes and toxic metabolites (i.e. lactic acid and fatty acids), which are found in secretions (i.e. tears, saliva and sweat). They have a protective function to destroy bacterial cell walls.
Stomach acid and digestive enzymes, while also used for food digestion, can also kill pathogens. In females, the lining of the vagina is coated in acidic secretions that serve several functions, including defence against pathogens.
Microbiological barriers
Microflora are found on the sin and in the mouth, nose, throat, lower part of the gastrointestinal tract and the urogenital tract. Microflora prevents growth and colonization of other bacteria because microflora compete with pathogenic bacteria for space and resources and produce chemicals that reduce the pH of the micro-environment.
Koch’s postulates
- It must be shown that the microorganism is ALWAYS preset in the diseased organism.
- The microorganism must be isolated and grown in pure culture.
- Microorganisms grown in pure culture when injected into a healthy organism without the disease, must produce the disease.
- Microorganisms isolated from the experimental organisms, grown in pure culture, and compared with the microorganisms in the original culture, must be IDENTICAL.
Robert Koch
Robert Koch developed many agar techniques including one to culture micro-organisms. He also demonstrates that specific micro-organisms are responsible for causing specific disease.
- Identified the bacteria responsible for causing anthrax
- Identified the bacterium responsible for causing tuberculosis and cholera
Koch’s experiment
Koch’s experimental method involved examining blood samples taken from patients with different diseases, then growing microbes from the blood on nutrient plates. When he injected specific microbes into mice, he found that they developed disease similar o the original patient.
AS A RESULT –> specific microbes causes specific diseases.
Pasteurisation
Process of heating up and cooling down food, eliminating pathogens. Now implemented in restaurants. Led to sterilisation of medical equipment.
Louis Pasteur works
Louis Pasteur was responsible for identifying microbes as the agents responsible for spoilage. Pasteur managed to disprove the theory of spontaneous generation by demonstrating that all micro-organisms come from pre-existing organisms (germ theory of disease).
His work significantly changed the way that we treat and prevent infectious diseases. He uncovered the relationship between microorganisms and disease, He established the principle of immunity on which vaccination methods are based. His ideas were able to be used by Koch to establish his postulates. Modern medical approaches to disease, including using antiseptics and hygiene practices to reduce exposure to microorganisms are results of the findings of Pasteur’s work.
Through this, he demonstrated that microbial growth was a result of particles in the air and could not arise spontaneously in sterile environments. This led to the development of pasteurisation. pasteurisation is the process of heating up and cooling down food, eliminating pathogens. This finding contributed significantly to our understanding of the disease, as the scientific community began to accept those infectious diseases must be a result of micro-organisms, originating from one external source.
Louis Pasteur; Swan neck
• Swan neck flask - Broth placed in swan neck flask, boiled to get rid of micro-organisms, one flask was broken, and one was normal. Broken one had spoiled (proves that bacteria don’t just generate randomly, they come from exposure to the air) –> germ theory
Louis Pasteur; Anthrax experiment
• Anthrax experiment - had 2 vaccinations: one was regular pathogen and one was a weaker version. Those given regular died, those given weaker survived. Led to creation of vaccinations.
Infectious agent
This is the pathogen that is capable of infection. The ability of the pathogen to infect and cause harm is described as its virulence.
Example of disease in agriculture
-description
Late blight in potatoes
The Irish imported a variety of potato from South America that was eventually grown asexually (via vegetative propagation) to feed their growing population. This made them genetically identical. When the crops became infected by the fungal pathogen, Phytopthora infestans, the entire crop was destroyed due to lack of genetic variation, meaning all potatoes were susceptible to the disease.
The potato blight caused the Irish potato famine of the 1840s
Late blight in potatoes
- Type of pathogen
- Method of transmission
- Typical symptoms
- Treatment
- Disease prevention
- Disease control measures
- Effects
Fungus
Spores released (every 5 days) Wind and soil
Potatoes develop dark patches and then rot (making them useless)
None
Fungicide sprays
In response to the issues surrounding potato blight, scientists are developing genetically engineered potatoes with blight resistance.
This can reduce the need for fungicides in the future which take a toll on the environment
Destroying crops with blight as well as a large surrounding area
- Infectious diseases impede a plants ability to function normally and therefore has a significant impact on the yield and quality
- Plant diseases cost millions each year and impacts our ability to trade (locally and internationally)
- It is estimated that pathogens cause 12.5% crop loss globally
- Significant social impacts (potato famine of 1845-1849)
- Adverse effect on biodiversity in natural ecosystems.
Example of disease in animals
- description
Bovine spongiform encephalopathy (BSE)/ Mad cow disease
BSE is a transmissible, slowly progressive, degenerative, and fatal disease affecting the central nervous system of adult cattle.
BSE spread through the indirect transmission in food to other cattle. Controlling this spread involves culling animals, which has a significant impact on food production.
Mad Cow Disease
- Type of pathogen
- Method of transmission
- Typical symptoms
- Treatment
- Disease prevention
- Disease control measures
- Effects
Prion
Origination: unknown
The disease may also have just appeared when a random protein became distorted.
Transmission occurs when cows who died of BSE were ground up and fed to healthy cows. It is possible that a version of the disease transmitted to humans because of infected meat (causing CJD).
The infectious agent that causes mad cow disease is an abnormal version of a protein normally found on cell surfaces, called a prion. For reasons still unknown, this protein becomes altered and destroys nervous system tissue – the brain and spinal cord.
Severe brain and nervous system damage leading to trouble walking and standing and changes in mood; possibly causing increased aggression or nervousness.
No treatment or cure
Controls on animal feed, and removal of the parts of cattle (nervous system tissue) most likely to carry BSE infectively
People who lived in high-risk areas for a period of time or had a blood transfusion can’t donate blood
Economic:
o Animal diseases pose a major threat to Australia’s economy
o Food security
Health risks:
o Animal diseases have the potential to infect humans
Antigens
Hint: two types
The innate immune system is activated by the presence of antigens and their chemical properties. Antigens allow the body to recognize potentially harmful pathogens and begin an immune response.
Antigens are markers present on the surface of all cells. Each type of cell has a certain antigen which allows the antibodies to recognise them. The body is able to recognise foreign pathogens by ‘non-self’ antigens.
Reliability
Repeat the steps multiple times
the reliability of the experiment could be assessed by looking at how many times the experiment was repeated by different individuals, the sample size and the average of the results
Dependent vs independent variable
The dependent variable is the variable that is being measured or tested in an experiment.
The independent variable cause changes in the dependent variable.
Control
size of the test tube, amount of nutrients available, number of initial bacteria, total time of incubation
Aim
To demonstrate the effect of tempreture on bacterial growth.
components of the innate immune system
phagocytosis
natural killer cells
inflammation
the complement system
what is direct contact (mode of transmission)
physical contact between an infected organism and a susceptible organism allows the transfer of infected bodily fluids
person to person
droplet spread
e.g. of diseases that come from person to person contact (direct)
STD’s, ring worm, needle injections
e.g. of diseases that come from droplet spread (direct contact)
tuberculosis, measles, small pox
what are types of indirect contact?
airborne
contained object (fomites)
contaminated food and drinking water (vehicular)
explain fomites as a type of indirect contact + e.g.
when organisms can live on objects or a short period of time e.g. door knob, railing…
E.G. E. Coli
what is kochs postulates?
list of criteria which must be met to prove that a particular organism causes a particular disease
Testing for microbes
- aim
- hypothesis
- materials
- Method
- Variables
- Conclusion
- Risk assessment
aim: to investigate the presence of microbes in different water sources
hypothesis: that water extracted from the pond will contain different microbes than sterilised water
materials: Agar plates, parafilm, sterilised water, bond water, inoculating loop, insulator, bunsen burner
method:
sterilise
bunsen burner –> loop
label control and pond water plates
using an inoculating loop swab agar plate with sterilised water and seal
incubate plates for three days at 30 degrees
remove plates from the incubator and observe colony growth.
record observations of types of microbial growth, taking notes of colours, size and frequency of colonies
variables:
independent: type of water (pond of sterilized)
dependent: types of microbial growth
controlled variables: temperature, incubation period, amount of water
controls: agar plate inoculated with sterilized water, agar plate left uninoculated
conclusion:
different types of microbes are present in different types. of water and therefore can be found in different environments.
Testing for microbes
- aim
- hypothesis
- materials
- Method
- Variables
- Conclusion
- Risk assessment
aim: to investigate the presence of microbes in different water sources
hypothesis: that water extracted from the pond will contain different microbes than sterilised water
materials: Agar plates, parafilm, sterilised water, bond water, inoculating loop, insulator, bunsen burner
method:
sterilise
bunsen burner –> loop
label control and pond water plates
using an inoculating loop swab agar plate with sterilised water and seal
incubate plates for three days at 30 degrees
remove plates from the incubator and observe colony growth.
record observations of types of microbial growth, taking notes of colours, size and frequency of colonies
variables:
independent: type of water (pond of sterilized)
dependent: types of microbial growth
controlled variables: temperature, incubation period, amount of water
controls: agar plate inoculated with sterilized water, agar plate left uninoculated
conclusion:
different types of microbes are present in different types. of water and therefore can be found in different environments.
risk of infection by microbes
precautions: wear PPE (glasses), wash hands before and after
water spillage: take care not to spill water and wipe up all spillages immediately. Do not perform experiment close to electrical outlets
open flame: PPE, tie hair back
response: seek medical assistance if injury occurs
explain fomites as a type of indirect contact + e.g.
when organisms can live on objects or a short period of time e.g. doorknob, railing…
E.G. E. Coli
list kochs postulates
- in all organisms suffering from disease, the microorganisms must be present in abundance
- microorganisms must be isolated from the diseased organisms and grown in pure culture.
- When a healthy organism is inoculated with the pure culture, it must develop the same symptoms as the original sick organism
- isolated and re-grow the microorganism from the newly infected organism. if it is identical to the microorganism cultured in step 2, it has been identified as the cause of the disease.
Explain how the immune system responds after a primary exposure to a pathogen, including innate and acquired immunity.
the immune system enacts a coordinated response to pathogen exposure, mediated predominantly by white blood cells, B cells and T cells.
- when a pathogen first enters the body, it is detected as foreign due to the presence of non-self antigens on its surface
- inflammation allows increased blood flow to the site. increased permeability of blood vessels allow the white blood cells to migrate from the blood into infected tissue.
- Non-specific responses, including phagocytosis, occur. Macrophages engulf pathogens which they encounter and release cytokines to call other immune cells to the site of infection
- the macrophages present the foreign antigens on their surface for recognition by B cells and T helper cells which are recruited to the site by interleukins (type of cytokine).
- B and T cells specific to the pathogen are selected by the antigens (clonal selection).
- B cells differentiate into plasma cells and secrete pathogen-specific antibodies to immobilise the foreign cells.
- cytotoxic killer T cells attack pathogenic cells by releasing cytotoxins (e.g. perforin)
- memory B and T cells are produced
- pathogen is cleared from the site
- suppressor T cells come in and dampen the immune response, suppressing Killer T cells once the infection has passed
- Memory B and T cells remain circulating in the blood to provide long-term immunity.
Vaccination and the secondary immune response
Vaccination utilises this secondary response by exposing the body to the antigens of a particular pathogen and activates the immune system without causing disease.
Subsequent doses of the vaccine act to boost this response resulting in the production of long-lived antibodies and memory cells, as it would naturally following subsequent infections.
The aim of vaccines is to prime the body, so that when an individual is exposed to the disease-causing organism, their immune system is able to respond rapidly and at a high activity level, thereby destroying the pathogen before it causes disease and reduces the risk of spread to other people.
Active immunity
Occurs when a pathogen triggers an immune response, and this can occur through:
• Natural infection
• Injection with vaccination.
Passive immunity
Passive immunity
Occurs when a person is given antibodies:
• IgG bodies can be passed from mother to unborn child.
• IgA bodies can be produced through mother’s milk.
• A person may be given immunoglobin protection for a specific disease (for example, immunodeficiency diseases).
Acquired/ adaptive immune system
if the innate immune system response fails to kill an invading pathogen, the final line of dance: the highly specific acquired/ adaptive immune system comes into action.
The adaptive immune relies on B and T cells that are both lymphocytes made in the bone marrow.
B cells
After formation and maturing in the. none narrow, naive B cells move into the lymphatic system to circulate throughout the body. if a naive B cell encounters its own specific antigen that fits its membrane-bound antibody, it quickly divides in order to become either a plasma B or memory B cell.
Plasma B cells
- Presence of antigen stimulates cells to differentiate into plasma cells
- Plasma cells produce immunoglobins called antibodies that bind with a specific antigen
memory B cells
- Remain in the body after infection to recognize later infections
- Produce secondary response that is faster
T cells
once formed in the bone marrow naive T cells migrate to the thymus to mature and become T cells. The antigens are bound to certain receptor molecules, called Major Histocompatibility Complex class 1 (MHCI) “SELF” and class 2 (MHCII) “NON SELF”.
T-helper cells
Stimulate the production of plasma cells by activating B lymphocytes and T cells to divide
Cytotoxic T-cells
- Destroy cells that are recognized as foreign
* Attach to a cell surface and release chemicals
Supressor T-cells
Turn off the immune response and suppress the production of antibodies
Memory T cells
- Responsible for the secondary response
* Clone when activated by an antigen after re-exposure
Malaria vaccine example
the malaria vaccine would stimulate the person to produce antimalaria plasmodium antibodies, memory B and Memory T cells. On future exposure to the plasmodium. the immune response would be rapid and the plasmodium will be destroyed before the person develops the disease. If a;; individuals in a population are vaccinated, that person will not be present in blood and therefore will not be transferred to others via mosquitoes. In his way, occurrence and spread will be limited.
Antibody vs cell mediated immunity
There are 2 mechanisms of adaptive immunity:
• Antibody-mediated immunity (or humoral immunity) secretion of antibodies into extracellular fluid by B lymphocytes
• Cell-mediated immunity activation of T lymphocytes
Innate immune system
The innate immune response is a non-specific mechanism that involves the identification of pathogens that pass through the first line of defence, and the destruction of those pathogens. Innate immune responses are:
• Non-specific, meaning they do not attack specific antigens
• Rapid, occurring within hours
• Present in all organisms
• Fixed responses that do not adapt
• Unable to lead to immunological memory.
Phagocytes
These are leukocytes that engulf and break down pathogens in a process known as phagocytosis. Phagocytes include: • Neutrophils • Macrophages • Monocytes • Dendritic cells
In phagocytosis the phagocyte will engulf the microbe, with the cell membrane forming a vacuole (phagosome) around it. A lysosome, containing digestive enzymes (lysozymes) fuse with the phagosome to form a phagolysosome, which breaks down the foreign material. The dead remnants are expelled from the body via exocytosis.
Natural Killer Cells
Natural Killer Cells are that cells that attack viral-infected body cells. They are able to recognize cell surface markers (antigens) on body cells and destroy them by producing chemicals called perforins which are able to bind with foreign cell antigens on the surface and form pores (holes) that cause the cell to lyse (release cell contents). After the NK cell detects an infected or tumour cell, it induces programmed cell death, or apoptosis. Phagocytic cells then come along and digest the cell debris left behind.
Complement proteins
Complement proteins: array of proteins that circulate the blood and help kill foreign cells.
Cytokines: signaling molecules that coordinate many aspects of the immune response. There are two types:
• Interferons – are produced by, and act on, an infected host cell. They activate host cells to produce enzymes that break down viral RNA and proteins that block translation.
• Chemokines – attract leukocytes to the sites of infection and inflammation.
Inflammation
Interaction between leukocytes and pathogens triggers the inflammatory response. The inflammatory response is responsible for releasing several types of chemicals that enable the activation of phagocytes and other white blood cells to fight foreign substances.
The body sends blood and fluid to the site of injury or infection, making it red, hot and swollen., allowing more blood flow to site of infection and increases access for phagocytes to enter).
Part of the inflammatory response is fevers. Fevers increase body temperature above normal (37 degrees) which slows pathogenic replication, allowing time for defenses to intervene. Moderate increases in temperature increase the activity and proliferation of leukocytes, so fever improves the immune response.
