10. Disease Aetiology Flashcards
(36 cards)
1
Q
Define ‘disease aetiology’
A
the study of causation
2
Q
Impact of black death in Newcastle
A
- May 1636 12,000
- December 1636 6000
- plague/black death caused by ‘miasma’
- treated with blood letting to rebalance humours
3
Q
Explain miasma theory
A
- bad air causes disease
- foul smells
4
Q
What bacteria causes the plague?
A
gram negative rod shaped Yersinia pestis
5
Q
When was bacteria first observed?
A
1670s
6
Q
What did the Roman poet Lucretius say about disease?
A
- the world contains various ‘seeds’
- some of which can sicken a person if inhaled or ingested
7
Q
First observations of bacteria
A
- van Leeuwenhoek
- made his own microscopes and studied dental plaque
- described animalcules (some motile)
- termed as bacteria in 1864 (much later not by him)
8
Q
What did Edward Jenner do?
A
- reports vaccination with Cowpox to prevent Smallpox
- used evidence inoculation can protect against smallpox
- pioneered term vaccination
9
Q
What did Ignaz Semmelweis do?
A
- studied puerperal fever (infection of placental site in uterus after birth in mother which leads to sepsis and death)
- in 2 maternity clinics, one with med students only and one with midwives
- medical students coming straight from autopsies and not washing hands and he proposed cadaveric contamination theory
- proposed hand washing in chlorinated lime as he knew it removed smell of autopsy tissue
- reduced mortality rates in clinic with med students
10
Q
What did John Snow do?
A
- linked cholera outbreak to a single water pump on Broad Street
- realised majority of cases were centred around it and removed the pump handle
- cases subsided and despite lack of conclusive results from testing the water it was the first study to trace the source of an infectionWh
11
Q
What bacteria causes cholera?
A
vibrio cholerae - gram negative motile rod shaped bacteria
12
Q
What did Louis Pasteur do?
A
- miasma still accepted but thinking was that living organisms can spontaneously generate from abiotic particles in air (spontaneous generation theory)
- Pasteur investigated fermentation and wine spoilage convinced microorganisms played a role
- found heating liquids above 60 degrees prevented spoilage of wine, beer and milk (pasteurisation)
13
Q
What did Koch do?
A
- looked at ways of growing pure cultures of microorganisms using a range of nutrients leading to development of agar
- first to prove a specific microorganism causes disease (bacillus anthracis) and disproved miasma, spontaneous generation and proving germ theory
- worked on TB too
14
Q
3 types of anthrax
A
- pulmonary
- cutaneous
- gastrointestinal
15
Q
Explain the bacillus anthracis bacteria
A
- gram positive
- endospore forming
- rod shaped
- soil bacterium
16
Q
Endospores from anthrax have a … cell wall and are resilient/easy to kill
A
- thick multilayer
- resilient
17
Q
Why are cows so susceptible to anthrax?
A
it’s a soil borne disease and they’re low grazing animals
18
Q
When has anthrax been used as a weapon?
A
as a biological warfare agent
- WW1 by Germany to infect cattle
- 1932 - by Japan against China
- 1942 - GB and USA experiment in Scotland
- 2001 - USA postal attack
19
Q
How did Koch link bacillus anthracis to anthrax?
A
- he was medical orfficer in Wollstein studying medicine
- over 4 years, over 500 people and 56,000 lifestock died of anthrax
- he reported presence of microorganisms in blood of animals
- set up experiments to prove they were the cause
20
Q
What were Koch’s postulates?
A
- the organism must present in all cases of disease and not in healthy individuals
- organism must be isolated in pure culture
- isolated organism must cause disease in suitable animal
- organism must be reisolated from infected animal
21
Q
Path of Ebola through it’s symptoms
A
- day 7-9 get headache, fatigue, fever, muscle soreness
- day 10 - sudden high fever, vomiting blood, passive behaviour
- day 11 - bruising, brain damage, bleeding from orifices
- day 12 - loss of consciousness, internal bleeding, death
22
Q
Ebola and Marburg disease have what in common?
A
they’re viral haemorrhagic fevers
23
Q
Where are Legionella bacteria found?
A
- naturally in water
- grow best in warm water e.g hot tubs, cooling towers, hot water tanks, large plumbing systems, air conditioning of buildings
24
Q
How do Legionella survive?
A
- within amoeba
- survive in otherwise harsh environments
25
How do dental practices adapt to Legionella risk?
from 2011, must have a risk assessment as can have contaminated water lines
26
Koch's first postulate of 'organism must be present all disease and not the healthy' has been adapted how to the modern world?
- asymptomatic carriers must be acknowledged for cholera, SARS-COV-2 for example
27
Explain asymptomatic carriage of neisseria meningitidis
- gram neg cocci bacteria
- can cause life threatening sepsis/meningitis
- we have a pharyngeal carriage resevoir for transmission and it's passed by close contact
- extremely high rate in teenagers especially at uni but not of the disease
- a study of uni students showed when first starting rates were 23% carriage, highered to 56% after first term
28
How is meningococci spread as of the university study in 2011?
- visiting hall bar
- being male
- active smoking
- night club visits
- intimate kissing
29
How has Koch's postulate 'organism must be isolated in pure culture' been updated for the modern day?
- viruses couldn't be cultured in early 1900s and some still difficult to culture
- prions are difficult if not impossible to culture
30
Rivers' updated postulates
- isolation of virus from diseased host
- cultivation of virus in host cells
- proof of filterability
- produce same disease in host
- re-isolation of virus
- detection of specific immune response to virus
31
Oral disease do/do not have a single aetiological agent.
What are they often?
do not
- consider changes in microbial community as agent
32
How is Koch's postulate 'isolated organism must cause disease in suitable animal' adapted to nowadays?
- animal models may not be available
- or representative of human disease
33
When can Koch's postulates not be used?
- no infecting organism can be detected
- organisms can't be grown in culture
- no suitable animal model
- more than one species of microorganism is involved
- if level rather than just presence of bacteria is important
- acquisition of virulence by commensal organism
- immunocomprimised host
34
... is used increasingly to detect infectious agents
DNA analysis
35
Why is DNA analysis used to detect infectious agents?
- circumvents isolation of infectious agent
- very sensitive (detects in absence of disease)
- can be quantitative (determine infectious load)
36
Many infectious diseases are now considered what?
imbalances/dysbiosis in hosts natural microbiota (polymicrobial)
