Hand washing lesson at Westburn

 

Last Thursday, I went in to Westburn armed with some agar plates. We talked about bacteria and what they do and the fact that many bacteria are helpful and useful. Then we talked about handwashing and how important it is to wash your hands, especially before eating and after going to the toilet.

Ten brave volunteers stepped up and put their hands onto agar plates, then washed their hands using the correct method, and put them onto the plates again. Check out the results........

The plates on the left of each photo are the ones cultured before handwashing for each person. Next to these are the plates cultured after the volunteers had washed their hands. You can see that there are still some bacteria left on their hands after washing, but nowhere near as many!

Blood

Here's a couple of questions for you, Room 3 aspiring scientists:
How do you think machines like this have changed the way scientists like Rosie do their jobs?
Do you think these changes are good or bad?
I would be interested in your comments, so post below.

Gram Staining - Why and How?

Gram staining is a procedure which is carried out to identify whether bacteria are Gram positive or Gram negative. This is usually the first procedure done in the process of diagnosing a bacterial infection. Gram positive bacteria have cell walls which allow the stain to absorb into the cell, so they will show up as a purple colour after the staining procedure.

The process is:

1. Prepare a slide of the sample you wish to analyse. This can be blood, sputum, tissue etc. In this case, we were using stored samples of the various bacteria so I could have a look at them.

Cultured plates

Slides

2. Once the slides have been prepared and dried, the gram staining is done. The first stain is called Crystal violet. This is applied to the slide and left there for 30 seconds.This is then rinsed off and iodine is applied for 30 seconds. This is then rinsed off and acetone is applied for 6 - 10 seconds. This takes the colour off the surface of the cells so that the only stain that will be left will be any that has been allowed into the cell by Gram positive bacteria. This is then rinsed off and a red stain called safranin is applied for 30 seconds. This is basically a stain which will stick to the bacteria so that they will show up under the microscope. It will change the colour of the Gram negative bacteria to a pink colour because there is no darker purple dye retained within the cells.

Here is a diagram of the process:

These pictures show how Gram positive and Gram negative bacteria look under the microscope:

Gram positive cocci

Gram negative cocci