Transcript Micro-organisms - Noadswood Science

Thursday, March 31, 2016
L.O: To understand the contributions of Semmelweis
in controlling infection
How does this
advert help to
control infection?
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One easy way to defend the body against illness is by keeping
it clean and hygienic as microbes can spread very quickly in
unhygienic conditions
The spreading of microbes is known as transmission
As soon as a virus or bacterium
enters the body, we are termed
infected (not the same as being ill –
illness results from the effects these
microbes have on our body
Bacteria and viruses have the ability
to produce poisons known as toxins
A scientist called Semmelweis collected this data. What do you
think could have caused the differences between the first
division and second division wards?
What would you investigate as a
scientist?
Semmelweis’s Discovery
Explain in your own words simply how
Semmelweis helped to control infection
In the late 1840's, Dr. Ignaz Semmelweis was an
assistant in the maternity wards of a Vienna hospital.
There he observed that the mortality rate in a delivery
room staffed by medical students was up to three
times higher than in a second delivery room staffed by
midwives. In fact, women were terrified of the room
staffed by the medical students. Semmelweis observed
that the students were coming straight from their
lessons in the autopsy room to the delivery room. He
postulated that the students might be carrying the
infection from their dissections to birthing mothers.
He ordered doctors and medical students to wash
their hands with a chlorinated solution before
examining women in labor. The mortality rate in his
maternity wards eventually dropped to less than one
percent.
Year
Amount of hand wash
solution used (litres per
1000 patient days)
MRSA infections per
100 patients
1993
3.5
0.50
1995
6.9
0.48
1997
10.9
0.25
Hospitals are trying to be more
hygienic
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In the late 1840’s Dr. Ignaz Semmelweis noticed that the
death rate in a delivery room was high
He thought that the doctors were carrying infections between
patients and ordered doctors wash their hands with a
chlorinated solution before examining women in labour
The mortality rate in his maternity wards eventually dropped
from twelve percent to less than one percent
The work of Louis Pasteur
Whilst investigating why wine went sour Pasteur discovered that yeast caused
fermentation, and bacteria caused the wine to go off. People found these results
surprising as they didn’t realise that bacteria could cause chemical changes.
Pasteur suggested that micro-organisms can cause disease, forming the basis of
the germ theory of disease.
Pasteur discovered that by heating
the grapes to a high temperature before fermentation,
the wine did not go sour, as the bacteria had been
killed. This technique is called pasteurization.
Pasteurization
Pasteurization is now widely used in food and drink production to prevent
unwanted (and potentially harmful) micro-organisms from growing.
There are several different types of pasteurization:
 conventional low temperature holding (LTH)
– liquid is heated to 60 °C for 40 minutes
 ultra-high temperature (UHT)
– 140 °C for 2 seconds.
Pasteurization using a higher temperature will kill off a wider range of microorganisms. In order to prevent contamination it’s also important that the
equipment used at each stage of food production is sterilized.
Microbial Practical
Your task:
To set up agar plates to test whether different
handwashes affect the growth of bacteria.
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Diseases can be transmitted via: 1. Droplet transmission (sneezes & coughs)
2. Water transmission (polluted water)
3. Vector transmission (animals)
4. Contact transmission (person to person)
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If an infected person sneezes or coughs, millions of microbes
are released into the air
These microbes could then infect somebody else…
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Microbes can feed off the pollution within water
If water is not cleaned, the microbes can reproduce and enter
the body when the water is drunk
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A vector is an animal that carries the microbe from one place
to another
Vectors can range from houseflies to pets
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Many microbes can be exchanged from one person to another
within bodily fluids e.g. blood and semen – this is how many
microbes responsible for sexually transmitted diseases are
spread from person to person
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The less hygienic people are, the
greater the chance of infection
Microbes will also reproduce rapidly in
unhygienic conditions – this is the
main reason why public places such as
restaurants have to abide by strict
hygiene regulations