Pathogens

PathogensWALT :• what pathogens are and how they cause us to feel ill• the history behind infection control

Starter: Complete Pathogen cryptogram then stick it in your book.

Bacteria on Roast Beef• Green blobs are

Salmonella bacteria• Probably got on

beef on the feet of a house fly

• If it is left in a warm place, the bacteria will multiply

• If you then ate it, the thousands of bacteria could make you very ill

X 2000X 2000

Microorganisms

• Living things that are too small for us to see without a microscope – they include bacteria and viruses.

• Visible organisms are made up of many cells. But each bacterium is made of just one cell – You could fit 1000 of them into 1mm

• Viruses are even smaller – you could pack 1000 of these inside a single bacterium

Microorganisms and Disease• Some bacteria and viruses cause

diseases = pathogens

• When bacteria enter the body,

they reproduce rapidly. They

may produce waste products

called ‘toxins’ that make you

feel bad. The toxins get carried

around in your blood so even if

the bacteria are only in one

place in your body you feel feel

the effects all over your body.

• A virus will actually get inside one of your cells and reproduce there.

• When lots have been produces they will burst out of the cell destroying it. The viruses then invade other cells.

Quick Questions

1. What does pathogen mean?2. How do bacteria make you feel ill?3. How do viruses damage the body?4. Arrange these in order, smallest

first:human cell, virus, bacterium

Ignaz Semmelweis• He was a Hungarian

doctor who worked in 2 labour wards in Austria in the 1840’s

• The wards were only cleaned once a month. Doctors didn’t wash their hands and often wore filthy coats

• He was horrified at the number of women who died after easy births – with very high temps – puerperal fever – no one had any idea of what caused the disease.

• Semmelweis noted that 3 times the number of women were dying in teaching ward compared to midwives ward

• He looked at what was different but couldn’t see much difference

• Then a professor was cut with knife that had been used on woman who dies from fever – the professor himself developed fever and died

• Semmelweis thought there must have been something on knife that had caused the disease

• He made all doctors wash their hands in chlorine water before examining the women and the death rate plummetted

Draw a flow chart to show the development of Semmelweis

discovery

What did he make the doctors do?What did he make the doctors do?

What did he observe? What happened to make him think?

What did he observe? What happened to make him think?

What horrified him?What horrified him?

What were the results?What were the results?

Who was he? Where was he working?

Heliobacter• A stomach ulcer is a sore raw patch in

stomach wall. Thought to be caused by stress or too much stomach acid.

• In 1982 two Australian scientists, Marshall and Warren, found bacteria in the stomachs of people with ulcers – they were spiral shaped so given name Heliobacter pylori (spiral bacteria of the stomach). They suggested that it was the bacteria that caused the ulcers

• No-one believed them so Warren swallowed some of the bacteria and as he expected he developed a stomach ulcer.

• Stomach ulcers are now treated with antibiotics, which kill the bacteria.

Now lets see how clean your hands are!

• In pairs place a piece of sellotape on the back of each of your hands and then lay it onto the agar

• Gently remove the sellotape from the agar and put the lid back on the plate

• Mark your plate with your initials and date and then seal the plate with two pieces of tape in a cross

• Place your plate back in trap for incubation.