VOLUNTEER: Wow, what a difference. I’m going to wash my hands right away.
VAN DER ZWALUW: These volunteers...
are going to press their hands into an agar plate.
The plate is very large, chosen...
especially for this demonstration...
so it is big enough for an adult hand.
Covered in a growth medium for culturing bacteria.
Whatever is on their hands will grow here.
We will also look at what grows after they wash their hands.
VEENSTRA: You encounter viruses and bacteria all around you.
But your hands are the main way...
that they are transferred from other...
surfaces to your mouth or eyes.
That is how you get infected.
When you wash your hands, you remove some of the bacteria and viruses...
although not all of them. That makes it much less likely that you will be infected.
By washing your hands, you can wash away those temporary visitors, the transient flora.
And then only the good bacteria, your own flora, will be left.
You don’t have to wash your hands over and over all day.
There are several times that it is advisable. If you remember those...
you will have the most important moments covered. Most of them are familiar.
After using the toilet - we all know that one.
And before preparing food.
But there are other times when you might have more pathogens on your hands.
Like after working in the garden, touching animals, or changing a baby’s nappy.
That is when you know that it is time to wash your hands again...
to minimise what is on your hands.
VAN DER ZWALUW: We took handprints from the volunteers.
We incubated the handprint plates for two days at 37 degrees.
Bacteria like that temperature; it helps them grow.
Everywhere that the plate came into contact with bacteria, they formed a colony.
A small circle of identical bacteria, which are descended from that contact.
Now we will look at the differences between an unwashed hand and a washed hand.
Let’s start with the handprints from before washing hands. We will start with your hand.
The whole outline of your hand is visible...
and you can see a beautiful range of different bacteria growing there.
And here’s your hand after you washed it.
As you can see, you cannot wash everything off completely.
But there is a lot less, and fewer different types.
This is a great example.
VOLUNTEER: And that is before washing?
VAN DER ZWALUW: Yes, this is before washing. This is your hand.
You can see very clearly here, after you washed your hands...
there is a distinct decrease in yellow colonies.
This confirms that washing your hands helps reduce transmission of diseases.