5. Infection Biology Flashcards
1
Q
What are obligate aerobes?
A
Organisms that require oxygen for cellular respiration
2
Q
What are obligate anaerobes?
A
Organism that produced energy for metabolism by fermentation or anaerobic respiration. They are poisoned by oxygen.
3
Q
What are facultative anaerobes?
A
Organisms that use oxygen when it is present but respire anaerobically or use fermentation in anaerobic conditions, to survive.
4
Q
What roles do prokaryotes play in chemical cycling?
A
Chemoheterotrophs = decompose waste products + dead material
Nitrogen fixers = fix N2 in the air into useable ammonia
Increase availability of N, P and K for plant growth
They can also immobilise / decrease nutrient availability
5
Q
How are bacteria involved in agriculture?
A
Nitrogen fixing for fertiliser, nutrient recycling, organic material decomposition
6
Q
How are bacteria involved in food?
A
Fermented food, preservation, meat substitutes
7
Q
How are bacteria involved in energy?
A
Biofuels (methane), bioremediation, artificial photosynthesis
8
Q
How are bacteria involved in biotechnology?
A
GMO, gene therapy
9
Q
How are bacteria involved in disease?
A
Treatment and care, infection
10
Q
What type of DNA do bacterial cells have?
A
A bacterial chromosome is a single, large, double-stranded molecule. Sometimes there are small circular plasmids which are additional DNA
11
Q
What is the average overall size of bacterial cells?
A
<1-10um (micrometres)
12
Q
Bacterial cells often lack membrane-bound organelles, what are some exceptions? (two examples)
A
Acidocalcisomes have membrane-bound acidic calcium storage compartments
Anammoxosomes have membrane-bound organelles that produce energy for anaerobic ammonia oxidation
13
Q
A
14
Q
What are the general components of a bacterial cell?
A
Cytoplasm
Cytoplasmic membrane
Cell wall
Capsule
Plasmid DNA
Single chromosome
Ribosomes
Flagellum
15
Q
What is the general structure of flagella and how do they work to allow motility for bacterial cells?
A
16
Q
What are fimbriae?
A
Relatively short extensions from the cells that allow them to stick to their substrate or others in the colony. AKA attachment pili
17
Q
What are sex pili?
A
Extensions from the cells that allow prokaryotes to exchange DNA. They are longer than fimbriae.
18
Q
What is the purpose of bacterial cell walls?
A
Shape / structure
Protect them from osmotic lysis and toxic substances
19
Q
What is the composition of the bacterial cell wall?
A
Made of peptidoglycan (polymer)
20
Q
How can the bacterial cell wall be used to classify bacteria into 2 groups?
A
Different compositions of the peptidoglycan polymer can be differentiated by Gram staining. (stain developed by Hans Christian Gram)
DESCRIBE DIFFERENCES
21
Q
What is the capsule which covers many prokaryotes?
A
It is an additional polysaccharide or protein layer.
22
Q
What do the colours produced by gram staining mean?
A
Purple = Gram positive bacteria. Peptidoglycan traps crystal violet.
Red-pink = Gram negative bacteria. Crystal violet is easily rinsed away.
23
Q
LECTURE ON FRIDAY 25/10/24
A
24
Q
How do microbes colonise
A
air, water, soil, food, animals
25
What makes a microbe beneficial or harmful?
Beneficial microbes have symbiotic mutual and commensal relationships.
Pathogens have symbiotic parasitic relationships, they damage the host during growth and have mechanisms of pathogenicity.
26
How do we provide microbes with good, diverse habitats for colonisation?
Factors important for growth are constant in a given niche:
Skin = dry and salty
Armpits = damp, warm, salty, low pH
Respiratory tract = moist, neutral pH, high in oxygen
GI tract = wet, warm, low pH, low in O2
27
Exposure?
28
What is the role of normal microbiota?
They protect surfaces from physical colonisation by pathogenic bacteria from animals, other humans, the environment, evolution of organisms.
29
What is the microbiome?
The microbes, their genomes and the environmental interactions in a define environment (e.g. GI tract in human microbiome)
30
How many cells / organisms make up the human microbiome?
number of human cells x10 = number of viruses and bacteriophages that make up the human microbiome
31
Gut microbiome
32
Are changes in human microbiome associated with human health or disease?
Yes, e.g. obesity, diabetes, asthma, cancer, autism, depression
33
How do we investigate the microbiome?
Whole genome sequences (e.g. Human Microbiome Project)
34
SLIDE 18 GUT MICROBIOME SLIDE
35
How can microbes be passed between humans?
Saliva
Aerosol transmission (sneezing)
Poor hygiene (not washing hands)
Insect bites
Cuts in skin
Sex
36
What is enteric bacteria
Bacteria that live in the GI tract
37
Describe the principles of pathogenesis
1. Invade host
2. Evade innate local defences + spread through host
3. Multiply
4. Evade adaptive immune defences long enough to complete life cycle
5. Leave body and spread to new hosts
38
Give an example of how bacteria invade a host (tooth decay)
Bacterial micro-colonies grow attach to the tooth and grow on its surface. The bacteria then ferments sugar to lactic acid causing decalcification of enamel (tooth decay)
39
Describe how toxins work in relation to cholera
Toxin gene is phage encoded and induces severe diarrohea.
WHAT IS THIS SLIDE ABOUT
40
How is necrotising fasciitis caused?
Bacteria invade the body and produces a toxin that can lyse (split / break down) red blood cells
41
SLIDE 31 what is going on
42
How to prevent infection?
Good hygiene
Vaccines
Antibiotics
Anti-viral agents
43
How do vaccines work to prevent infection?
It stimulates / activates protective defences of the body. Body generates memory response so that if infected, it will clear infection rapidly.
44
How was the first antibiotic discovered and how does it work?
Alexander Fleming discovered the fungus Penicillium notatum which produces penicillin which kills bacteria by preventing peptidoglycan cross-linking and therefore bacteria lyse under osmotic pressure.
45
How do viral agents work?
They inhibit the multiplication of the virus without affecting the infected host cell
46
How does Acyclovir (zovirax) work?
47
How does AZT (zidovudine) work?
48
How does Oseltamivir (tamiflu) work?
49
What microbes are involved in the production of bread, beer, cheese and vinegar?
Bread = Yeast
Beer = yeast
Cheese = Rhizopus chinensi
Vinegar = Acetoobacter
50
How is beer produced?
1. Ferment partially germinated malted barley
2. Heat to 65C to kill dangerous microbes
3. Add yeast which ferments sugar in barley
4. Alcohol is produced after fermentation
5. Yeast is removed, beer filtered, pasteurised, bottled
51
How is cheese produced?
Cheese used to be made by rennet but is now made by microbes.
1. Rennet is added to pasteurised milk is separate it into curds and whey
or
1. Microbes separate pasteurised milk into curds and whey (Rhizopus chinensis = bread mold / CM Aspergillus niger)
2. Flavour and form cheese by adding microbes during maturation + other processes
Rennet is mainly chymosin (aspartic acid protease) and was originally sourced from the the inner mucosa of 4th stomach of calf
52
How is vinegar produced?
1. Expose wine to air contaminated with Acetobacter which oxidises alcohol to acetic acid
Commercial process:
1. ethanol is produced by yeast
2. Acetobacter converts it to acetic acid
Non-brewed condiment is a vinegar substitute made of water, acetic acid, flavourings and colouring
53
What is pruteen?
Pruteen was the 1st single-celled protein animal feed made from CONTINUE THIS
54
How are microbes involved in reducing pollution?
Break down organic matter in sewage.
Bioremediation
Produce biodegradable plastic
55
What is the activated sludge process and what does it involve?
The breakdown of sewage.
Autotrophs require CO2 and use inorganic compounds for energy.
Heterotrophs require
56
What is bioremediation?
The use of microbes to break down dangerous chemicals.
57
Give an example of bioremediation (Alcanivorax borkumensis = oil)
FINISH THIS
58
Talk about the plastics
59
How are microbes used in medicine?
Produce large quantities of useful compounds (already produced by the bacteria or GM for exoogenous molecules)
Produce vaccines, complex vitamins, antibiotics
Human gene therapy (viruses)
60
What does exogenous mean?
non-native molecules (e.g. useful products that are produced by bacteria which are not naturally encoded in the bacterial genome)
61
How can an exogenous
high pressure, lysozymes, sonification
62
How can exogenous proteins be produced by bacteria?
63
SLIDE 23
64
Why is it safer to produce drugs from bacteria than blood? Give examples of such drugs.
Not infected / contaminated by viruses (e.g. HIV)
- insulin (diabetes)
CONTINUE
65
What is human gene therapy?
Alteration of faulty version of gene to treat disorders.
66
Explain the process of human gene therapy using viral vectors.
SLIDE 26
67
What are the risks of human gene therapy?
SLIDE 28
68
HISTORY OF EPIDEMICS LECTURE 1
69
What is an endemic?
A disease that is always present in an area, at a low but constant level.
70
What is an epidemic?
An outbreak of a disease (infectious or other condition e.g. obesity) that affects a large number of individuals at the same time.
71
What is a pandemic?
A global epidemic spreading across countries or continents.
72
Give examples of human behaviours that influence outbreaks in disease epidemics.
Exploration
Change in trade patterns
Globalisation
Warfare
Famine
Poverty, overcrowding, poor living conditions
Deforestation and encroachment of jungles
73
What is zoonosis?
The transfer of disease from animals to humans.
74
Around __% of human infections are zoonotic
60
75
How are zoonotic diseases transmitted? (5)
Food
Water
Vectors
Direct contact with animals
Proximity / indirect contact with animals
76
How do animals come into contact with humans to spread zoonotic diseases?
Intensive wildlife FARMING
Wildlife HUNTING
Live animal MARKETS
Domesticated animals (PETS)
Exotic pet TRADE
77
State other routes of emergence (that aren't zoonosis)
Natural disasters (cholera)
Mutation and adaptation (flu)
Disseminate from an isolated population to naive population thought it was benign (Zika virus)
Reappear after a period of absence (plague)
Appear out of nowhere = environmental
78
How is the plague transmitted? What is its causative agent?
via fleas on rodents. Bacteria
79
How is Syphilis transmitted? What is its causative agent?
via sexual contact. Bacteria
80
How is Typhus transmitted? What is its causative agent?
via contact with fleas. Bacteria
81
How is Typhoid transmitted? What is its causative agent?
via contaminated food or drink. Bacteria
82
How is Cholera transmitted? What is its causative agent?
via contaminated food or drink. Bacteria
83
How is Smallpox transmitted? What is its causative agent?
via airborne water droplets. Virus
84
How is Influenza transmitted? What is its causative agent?
via airborne water droplets. virus
85
How is Polio transmitted? What is its causative agent?
via person-person contact. virus
86
How is HIV transmitted? What is its causative agent?
via bodily fluids. virus
87
How is Ebola transmitted? What is its causative agent?
via bodily fluids. virus
88
Give examples of pandemic causing bacterial diseases. (5)
Plague, Syphilis, Typhus, Typhoid, Cholera
89
Give examples of pandemic causing viral diseases. (5)
Smallpox, Influenza, Polio, HIV, Ebola
90
LECTURE 25 BELOW
91
What are parasites?
Eukaryotic organisms that feed on their host to obtain organic nutrition. Parasites are often adapted to the host and cause some degree of harm to the host.
92
Define parasitism
Relationship between species where one (parasite) benefits and the other (host) is harmed.
93
What are symbionts?
What is another name for the relationship between symbionts?
A species that benefits from its relationship with another species. The relationship is mutually beneficial / symbiotic (the other species benefits as well).
Mutualism describes the relationship between symbionts.
94
What are commensals?
What is the name of the relationship commensals have with other species?
A species that benefits from its relationship with another species. The other species is unharmed.
Commensalism
95
What are protozoa?
Unicellular parasites
either intracellular or extracellular
96
What are helminths?
Multicellular parasites
Helminths = worms in latin
either flatworms or roundworms
97
What are arthropods / ectoparasites?
Multicellular ectoparasites
They attach to the body to extract blood e.g. ticks and lice
98
Define a definitive host and how co-evolution of host and parasite has lead to them
Definitive host = the parasite will only grow in a specific host. Where the parasite completes its lifecycle.
Millions of years of co-adaptation with a specific host. Parasites have evolved to not kill the host therefor less pathogenic parasites are thought to be better evolved.
99
Describe the three types of parasitic protozoa
Amoeboid = simple life-cycle, multiply in host, direct transmission
Kinetoplastid = flagella is energised by an organelle called plastids. They can move.
Apicomplexa = Have a complex (set of proteins) at the apex that allow them to invade a target cell
100
What are kinetoplastid protozoa?
Unicellular parasites that have flagella energised by an organelle called a plastid. They can move.
101
What are apicomplexa protozoa?
Unicellular parasites that have a complex (set of proteins) at the apex that allow them to invade a target cell
102
What are the two types of parasitic helminths?
Nematodes = round worms
Platyhelminthes = flatworms
103
What are the two types of arthropods?
Insects
Arachnids
104
What are predators (in terms of parasites)?
105
What are parasitoids?
106
Describe the generic features of a parasitic lifestyle
107
What is the difference between infection and disease?
108
Define prevalence of infection (parasitism)
The proportion of a population infected (%)
or
The total number of infected in a country or across the world
109
Define incidence of infection (parasitism)
The frequency of a population acquiring infection in a unit time
e.g. 3% per week or 10 per year
110
Define intensity of infection (in terms of parasitism)
the number or density of parasites per host
111
Define mortality (in terms of parasitism)
The number of deaths in a give time
or
% of deaths in the infected case mortality)
112
Define morbidity (in terms of parasitism)
The level of ill-health or disability among all cases of infection or among the general population. (long term)
113
Define DALYs (in terms of parasitism)
Disability Adjusted Life Years
Used to measure morbidity
The number of healthy years lost to disease, disability or early death.
114
Describe the current status of the global health problem posed by parasites
115
What zoonotic disease is caused by Toxocara canis?
Toxocariasis
116
Describe the pathology of Toxocara canis.
Key words: definitive host, soft tissue, female dogs, pregnancy
Intestinal Helminth Parasite (roundworm)
Definitive Hosts: Dogs + Foxes
Accidental Host: Humans (zoonotic disease)
Disease: Toxocariasis
In humans, larvae migrate into soft tissue: liver, lungs, brain and eyes.
In adult female dogs, larvae do not migrate from tissues to gut of the dog unless they are pregnant. In this case, the larvae cross placenta to infect pups, and migrate into colostrum to infect milk.
117
Describe the basic features of the life-cycle of Toxocara canis
1. Eggs from soil hatch in stomach as the shell dissolved, releasing larvae
2. Larvae migrate to soft tissue in humans (lungs, liver, brain)
or
2. In dogs, larvae migrate to small intestine
3. Larvae mature to adult worms in dogs
4. Adult females release eggs in faeces of dogs which then infects soil
In adult female dogs, larvae do not migrate from tissues to gut of the dog unless they are pregnant. In this case, the larvae cross placenta to infect pups, and migrate into colostrum to infect milk.
118
How is Toxocariasis treated and why?
Anthelmintic drugs readily clear parasite. This is routinely carried out in pregnant females, and young pups.
Cannot be eliminated due to the fox population. However, make sure its kept out of domestic environment to reduce zoonosis.
119
What zoonotic disease is caused by Echinococcus granulosus?
Hydatid disease
120
Describe the pathology of Echinococcus granulosus
Key words: Definitive host, intermediate host, soft tissue, cysts
Helminth Parasite
Definitive host: Dogs + foxes
Intermediate hosts: Sheep
Accidental hosts: Humans (zoonotic infection)
Disease: Hydatid disease
Humans ingest parasite via infected sheep, and hydatid cysts grow in soft tissues (liver, lung, brain). Cysts continue growing (daughter cysts), causing damage to the human.
121
Describe the basic features of the life-cycle of Echinococcus granulosus
1. Egg released in dog's faeces
2. Intermediate host (sheep) ingest the eggs
3. Eggs hatch in intestinal tract
4. Parasite forms hydatid cysts which grow in liver and lung
5. Dogs eat sheep (in the past) and cycle continues
122
How is Hydatid disease treated and why?
No drugs. Only surgery. Therefore, prevent them by treating dogs with drugs.
123
What zoonotic disease is caused by toxoplasma gondii?
Toxoplasmosis
124
Describe the pathology of Toxoplasma gondii
Key words: definitive host, oocysts, tachyzoites, parasitophorous vacuole, bradyzoites, congenital toxoplasmosis
Protozoan parasite
Definitive host: cats
Intermediate host: rodents
Accidental hosts: humans and farm animals
Disease: Toxoplasmosis
In humans, oocysts develop into tachyzoites which attach and invade the cell (broad cell specificity), forms its own vacuole (parasitophorous vacuole) to avoid fusion with lysosomes, and rapidly divides to form daughter cells. Tachyzoites transform into bradyzoites to form dormant tissue cysts that stay in the body and can reactivate.
The parasite can cross the placenta and infect the foetus' brain, causing congenital toxoplasmosis.
125
Describe the basic features of the life-cycle of Toxoplasma gondii
1. Parasite infect epithelial cells of the intestinal tract of cats
2. Oocysts are released in the cat faeces
3. Oocysts infect humans, farm animals and rodents (muscles)
4. Cats eat rodents and cycle continues
126
How is Toxoplasmosis treated and why?
During pregnancy, stay away from cat litter, unwashed food and raw meat.
127
128
Describe the role of human and animal behaviour in the spread and acquisition of parasites
129
What factors contribute to parasite distribution? (3)
130
Define ectoparasites
Ectoparasites live on the external surfaces of their hosts.
131
Define endoparasites
132
Define zoonosis (in terms of parasitism)
An infection or disease that is transmitted from animals to humans
133
Describe the range of approaches taken to treat parasitic infection and why many of these are failing
134
LECTURE 27 BELOW
135
What are NTDs?
Neglected Tropical Diseases are a group of diseases that cause substantial illness to more than one billion people globally.
136
What makes them neglected?
They affect the world's poorest people where they lack the infrastructure and sanitation to be effectively treated. They also have a normal distribution for severity of pathology so only a small percent of people are severely effected.
137
Name the 3 main soil-transmitted helminths
Asacaris lumbricodoides
Trichuris trichiura
Ancylostoma/Necator (hookworms)
138
Describe the life-cycle of Ascaris lumbricoides
Simple, direct life cycle:
USE DIAGRAM AND HIS EXPLANATION TO COMPLETE THIS CARD
139
How is Ascaris lumbricoides treated?
Oral medicine: Albendazole, Mebendazole, Ivermectin
However the drugs don't change susceptibility to re-infection, and as only adult parasites in the intestinal lumen are removed, reinfection can be rapid
Improved sanitation, footwear for hookworm, vaccines are needed in future
Ivermectin is also effective against athropod ectoparasites as well as parasitic helminths
140
Describe the lifecycle of Schistosomiasis
1. Infected human or animal releases eggs
2. Eggs hatch in freshwater into larvae
3. Larvae swim and infect snails and multiply = mass "eradiaction" not the word = expands transmission potential
4. New larvae are released in the water and penetrate the human skin transforming into another larvae
5. New larvae mature into worms in blood supply of liver, intestines, bladder
6. Wormslay thousands of eggs that cause damage as they work through tissues
7. Egges released into the water in urine or feces and cycle restarts
141
NOT TOO SURE WHAT THE IMPORTANCE OF THIS SLIDE IS
Eggs released by adult worms in the vasculature become lodged in the liver, causing granuloma formation, fibrosis and hepatomegaly
One species, Schistosoma haematobium, locates in the bladder vasculature, damaging the wall, causing haematuria and, in time, bladder cancer
142
Why is Schistomiasis rapidly infectong children
Freshwateer
143
How to treat Schistosomiasis?
Medicines clear adult parasites but does not prevent re-infection.
Molluscide treatment of snail breeding sites but only works in "..." sites like ponds and lakes not rivers etc
Public health measures e.g. education and infrastructure
Vaccines needed in future
144
Describe the lifecycle of malaria NOT A CLUE
1. Human is infected by mosquito
2. Mosquito is infected by
3. Expansion stage at hepatic cell which produces an intermediate that infcets RBCs
4. Rupture erythrocyte
5. Gametocyte picked up by mosquito which causes a cyst in the gut of malaria which bursts releasing the sporozoites not a clue which causes malaria
145
What is the apical complex of malaria
merozoites
146
Describe the trend in fever in malaria
After being infected, RBCs take 48 hours to rupture releasing more merozoites. More RBCs can then be infected therefore there is a fever every 48 hours
147
Describe the symptoms of Cerebral malaria and why it is untreatable
Fever, seizure, coma, high mortality, rapid so cannot be treated in time by drugs
148
How does the sporozoite vaccine for malaria work?
149
Explain the selection for the sickle cell trait and what this means
150
How is malaria prevented and treated?
Vector control: Insecticide spraying, long-lasting insecticidal nets (bed nets), genetic strategies (sterile males, resistant mosquitos)
Anti-malarial drugs
Mosquitos quickly develop resistance to insecticides and anti-malarial drugs so more need to be developed
Vaccines
151
What are the three types of malaria vaccine?
Sporozoite vaccine, merozoite vaccine, gametocyte vaccine
152
How does the merozoite vaccine for malaria work?
153
How does the gametocyte vaccine for malaria work?
154
inverse distribution
what is it and how could it possibly be used for helminths as therapeutic agents
155
Solutions in fighting NTDs
Block transmission: sanitation and bednets
Better drugs: artemesin and ivermectin
New vaccines
156
What makes vaccines tricky for NTDs
Complex lifecycles with multiple stages in different tissues
High level of antigenic variation (genome constantly rearranging /. parasite not stable)
Multiple immune evasion strategies (e.g. sequestration)
Parasites are able to supress the immune system
157
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