Module Seven - Infectious Disease Flashcards
Causes of Infectious Disease Responses to Pathogens Prevention, Treatment and Control
What is an infectious disease?
- They are diseases caused by pathogens
- Communicable or contagious diseases are infectious diseases that can spread from one organism to another by direct or indirect transmission.
What is an infection?
It is the entry of a pathogen into body tissues and cells followed by multiplication of the organism.
What is a pathogen?
- Pathogens are any organism living in or on another organism that is capable of causing disease.
Types of pathogens: (size order)
- prions
- viruses
- bacteria
- protists (protozoa)
- fungi
- macroscopic parasitic animals (macroparasites)
What are the distinguishing features of a prion?
- defective from of a protein molecule
- does not contain RNA or DNA
- mostly attacks brain or nerve cells
What are the distinguishing features of a virus?
- non-cellular
- contains DNA, RNA and protein coat
- requires a living host cell to replicate
What are the distinguishing features of a bacteria?
- prokaryotic cell
- divides quickly and/or produces toxins
What are the distinguishing features of a protozoan?
- eukaryotic cell (single-celled organism)
- may have a complex life cycle
What are the distinguishing features of a fungi?
- eukaryotic cell with cell wall
- spreads via spores or rapid division
- some infect external skin and nails, while others enter the host’s body
What are the distinguishing features of a macroparasites?
- multicellular
- they typically don’t multiply in their final or definitive host, but instead produce transmission stages (eggs and larvae)
What is a protist?
- a group of eukaryotic, unicellular or colonial organisms that include protozoa such as Amoeba.
What is a prion?
- prions are infectious agents that only consist of protein
- they have no nucleic acid
- referred to as non-cellular pathogens
What is bacteria?
- prokaryotic, unicellular organisms
- DNA is contained in a single loop
- some bacteria have an additional circle of genetic material called a plasmid
What is the average size of bacteria?
1000 nano-meters (10^-9)
What is the average size of viruses?
Their size ranges from 20 - 40 nano-meters (10^-9)
What is the effect of prion diseases also known as transmissible spongiform encephalopathies (TSEs)?
- rare progressive neurodegenerative disorders that affect humans and animals.
- symptoms include spongiform changes associated with the loss of neurons (brain damage) and the inability of the body to induce inflammatory response.
- typically progress rapidly and always fatal.
What is spongiform?
The post-mortem appearance of the brain with large holes that show where cells have been destroyed.
What is a virus?
- microscopic pathogen
- typically a small piece of genetic material encased in a shell called a capsid.
- considered non-cellular pathogens
- while they are considered to be non-living, viruses have nucleic acid.
How do viruses cause disease?
- Alone, viruses can do little harm.
- If they enter a living cell, it will begin to replicate and causes disease.
- Because they replicate at an extraordinary rate and they contain nucleic acid means that they can mutate and evolve.
What is a plasmid?
- small DNA molecule found in cells (often bacterial cells)
- separate from the chromosomal DNA
- plasmid may contain genes that give the bacterium some advantage over other bacteria (eg. resistance to antibiotics)
What are microbes?
micro-organisms
What is the average size of protozoan?
- size varies
- most are less that 50 micrometers
How does bacteria cause disease?
- by secreting toxins (chemical change)
- invading cells (physical change)
- forming bacterial colonies that disrupt normal cell function.
How are bacteria classified according to their shape?
- spherical (cocci)
- rod (bacilli)
- spiral (spirilla)
- comma (vibrios)
- corkscrew (spirochaetes)
What is fungi?
- eukaryotic organisms
- include yeasts, moulds and crop-destroying rusts and smuts.
What are macroparasites?
- macro-organisms that cause disease
- can be direct or indirectly as vectors for disease
- includes roundworms, flatworms and anthropods like ticks, mites, lice and fleas.
Explain what a vector is and provide an example.
- an organism that transmits a disease-causing pathogen
- eg: mosquitoes are vectors of the malaria-causing parasitic protozoan
- a vector often carries one part of the life cycle of the pathogen from one organism to the next.
What is direct droplet transmission?
- droplet transmission of a pathogen to a new host over distances of one metre or less.
What is airborne transmission?
- the transmission of droplets containing pathogens over distances greater than one metre
What are fomites?
- inanimate objects that become contaminated by pathogens from an infected individual or reservoir.
How does direct transmission occur?
- direct contact with people (through touch, saliva, mucous, etc)
- direct droplet transmission
- pregnant women can transmit infectious diseases (eg. STDs) to unborn children via the placenta, during birth or through breastfeeding.
How does indirect transmission occur?
- transmission from fomites
- airborne transmission of droplets
- transmission from environmental reservoirs such as soil and water.
- transmission from contaminated food and drinking water
What is an epidemic?
It is an outbreak or unusually high occurrence of a disease in a population or region.
What is a pandemic?
It is an outbreak of a disease over a whole country or an a global scale.
Which pathogen can be anaerobic or aerobic?
Bacteria
What were Koch’s postulates?
1: It must be shown that the micro-organism believed to be the cause of the disease is always present in the diseased organism.
2: The micro-organism must be isolated and grown in a pure culture; that is, a culture only containing that macro-organism.
3: Micro-organisms from the pure culture, when injected into a healthy organism without the disease, must produce the disease.
4: Micro-organisms isolated from the experimental organisms, grown in pure culture, and compared with the micro-organisms in the original culture, are shown to be identical.
What was the theory of spontaneous generation?
It is an obsolete idea that certain life forms could arise from dust or dead tissue.
Eg. it was believed that mould and maggots would occur spontaneously from non-living matter.
What idea did Koch and Pasteur both provide evidence towards?
In the 1850s their research provided evidence that many diseases were caused by micro-organisms.
What did Koch show? (ANS are examples)
- Koch showed that bacteria were the cause of the disease called anthrax in horses, sheep, cows and humans.
- He also demonstrated that bacteria caused tuberculosis in humans.
Explain Pasteur’s experiment process on microbial contamination.
- Pasteur prepared a nutrient broth that was boiled to kill any micro-organism
- that broth was then poured into two swan-neck flasks
- the control flask is left alone, while the other flask’s neck is broken off
- microbial growth is observed and compared.
How did Pasteur’s conclusions change our understanding of the causes and transmission of infectious diseases?
Pasteur’s conclusions led to the wide acceptance that diseases are caused by microbes and can be transmitted from one host to another.
What did Pasteur’s work contribute to the development of?
- vaccinations for fowl cholera, anthrax and rabies
What are epithelial surfaces?
They are surfaces that line organs and blood vessels.
This includes the skin and the lining of gastrointestinal, respiratory and urogenital tracts.
What are extracellular pathogens?
Pathogens that grow within the tissues of the body and do not need to be in a host cell for growth.
What are extracellular pathogens?
Pathogens that grow within the tissues of the body and do not need to be in a host cell for growth.
What are intracellular pathogens?
Pathogens that grow and reproduce inside the cells of a host; all viruses are intracellular pathogens.
Explain ‘entry into a host’ in terms of the pathogens actions.
- some pathogens can cause disease on the surface of the skin.
- most pathogens must enter a host to cause disease.
- microbes enter through protective barriers and can be extracellular and intracellular.
What are the protective barriers of plants?
- they include physical barriers: thick cell walls, thick cuticles, and the presence of a secondary cell wall or thick bark.
- chemical barriers include antimicrobial compounds
What are protective barriers of humans?
- skin
- mucous membranes
- cilia in the respiratory tract
- surfaces of the body covered by microbes (normal body flora)
- chemical barriers found in body fluids and secretions, and the pH of fluids
- other bodily secretions such as oil glands and fatty acids
How does skin function against pathogen entry?
- mechanical barrier: unbroken skin protects other tissues, and collects and holds pathogens
- if the skin is cut, the blood produces a blood clot that seals the wound and prevents pathogens from entering
How do the surfaces of the body covered by microbes (normal body flora) function against pathogen entry?
- these microbes act as a physical barrier; they also reduce the area available for pathogens to attach and become established.
How do mucous membranes function against pathogen entry?
- they occur along the alimentary canal, respiratory surfaces and urogenital surfaces (eg. bladder)
- the mucous traps pathogens
How do cilia in the respiratory tract function against pathogen entry?
- cilia beat in one direction to sweep mucous containing pathogens and small particles out of the lungs; coughing helps to remove materials and pathogens from the lungs.
How do chemical barriers function against pathogen entry?
- found in body fluids and secretions, and the pH of fluids
- low pH on the skin discourages growth of microbes
- stomach juices are highly acidic and in this acidity, along with peristaltic washing and the thick mucous lining, make it difficult for microbes to colonise the stomach
How do other bodily secretions such as oil from oil glands and fatty acids function against pathogen entry?
- inhibit the growth of some bacteria and fungi
- some secretions contain antibacterial factors
What are cytotoxins?
- substances that are toxic and destructive to cells
What are the adaptations of viruses (intracellular pathogen) to facilitate entry into host cells and to change the biology of the host cell?
- after attaching to the host cell, the virus must enter to release its nucleic acid from the protective coat or lipid envelope
- viruses enter cells by either fusing with the membrane of the host cell or by forming a pore in the cell membrane of the host cell to deliver the genetic material into the cytoplasm.
What are the adaptations of bacteria (intracellular pathogen) to facilitate entry into host cells and to change the biology of the host cell?
- some enter host cells by phagocytosis (a function of macrophages)
- some have adapted to survive and replicate inside macrophages
- some invade cells by using adhesions, which bind them to deeper tissues (eg. alveoli)
- bacterial toxins aid invasion by breaking down specific host proteins and disrupting signalling pathways.
What are the adaptations of protozoans (intracellular pathogen) to facilitate entry into host cells and to change the biology of the host cell?
- intracellular parasites are much larger than bacteria, so they must expend energy to invade cells through a variety of complex pathways.
- as it moves through the cell, the protozoan secretes lipids that form a vacuole compartment in which the protozoan is protected
- from its compartment the protozoan takes up its nutrients from the host cell
What are the adaptations of fungi (intracellular pathogen) to facilitate entry into host cells and to change the biology of the host cell?
- some fungi enter host cells
- meningitis can be formed by a fungi which uses white blood cells to reach the host’s brain cells
Give an example of a disease that is directly transmissible.
Ebola Virus - transmitted though direct contact with bodily fluids of infected animals or humans.
Give an example of a disease that is in-directly transmissible.
Cholera - caused by bacterium and is transmitted through contaminated water
Give an example of a disease that is transmitted through a vector.
Malaria - is caused by a protozoan, spread through a mosquito.
What is a natural or innate immune response?
General, non-specific defense and response mechanisms, primed and ready to fight an infection at all times.
What kind of defence do plants and animals rely on for infections?
- innate immune responses and preformed defences.
(no adaptive immune system to infections)
pg. 137 and 150 contradict each other
- this needs confirmation!! if you see this Kha tu pls message me
What is a preformed defence?
- meaning ‘made beforehand’
- they are defence mechanisms that are primed and are ‘ready to go’, as compared to the responses that are induced by the exposure to a pathogen/
Passive, preformed defence mechanisms in plants include:
- physical and chemical responses
What are chemical barriers in plants?
(general: stored chemical compounds that protect the plant and/or are released upon infection by a pathogen, including: plant defensins and pH)
- secretory cells, glands and ducts which secrete defensive compounds
- phenolic compounds are secreted by some plants to discourage herbivores and inhibit some plant microorganisms
What are physical barriers in plants?
- properties of the plant surface including: waxy leaf cuticles and thickened, tough cell walls
- the presence of secondary cell walls
What are defensins?
antimicrobial or anti-fungal plant peptides
Defence response of an Australian plant to a named pathogen
139
what is the active response of a plant?
139
What is an inflammatory response?
inflammation of the tissue in response to an infection; designed to isolate and destroy the foreign particles, it also prepares the the tissue for healing.