Experiment with your own germs

 In the next activity, we want to learn about hand-washing, the most important mean of preventing the spread of infection. 

How does hand-washing reduces infections ? 

What is the difference when using soap or hydroalcoholic gel ? 

 Procedure : 

For your safety, please watch the following video « Aseptic techniques in the biology lab » : 

aseptic techniques : it is to insure no contamination occur. These are very used when you want to cultivate microorganims

 Sum-up the main points of the video : 

Especially, and for your safety, pay attention with

  • Insure all windows and doors are closed
  • Wear a lab coat
  • Remove your jewellery
  • Tie your hair
  • Clean the working area with alcohol (70%) or bleach
  • Gather all the equipment you will need near to the electric burner
  • Work quickly and efficiently
  • Work seating down

Vocabulary :

bleach = javel ;

Flaming = enflammer ;

agar plate = milieu de culture à base de gelose ;

to carry out = déplacer 

hazard = danger 

assessment = évaluation 

to handle = manipulr 

draft = brouillon 

draught = air flow = courant d’air 

sleeve = manche (chemise) 

to roll up = remonter 

ruber band = élastique 

to sterilize = stériliser 

to tight back = retourner 

to swop = échanger 

to flame = flamber 

a petri-dish = une boîte de Pétri 

the lid = le couvercle 

gently = doucement 

smooth = lisse 

identation = échancrure 

to drip = to drop = goutter 

to unseal = to open = ouvrir 

First activity :

Imagin a procedure, using the materials below and respecting aseptic techniques, to compare the action of soap/hydroalcoholic gel on microorganisms of your hands.

Materials :

  • 3 premade agar plates
  • permanent marker pen
  • electric burner
  • soap and hydroalcoholic gel

Prepare 3 agar plates. Here is the procedure :

Scientific laboratories with experimental tools and equipment.
  • weigh in the cup 0,4 g of agar and 0,8 g of “meat broth” (bouillon de viande) using the spatula. 
  • pour 28 mL of distilled water then agar into the beaker and mix. 
  • heat the mixture and mix until it becomes clear. You have to stop around 1 minute after the beginning of boiling. 
  • remove the beaker, using the metal clip. 
  • pour the hot agar into the 3 Petri dishes at a height of 0.5 cm.
  • let the Petri dishes cool without putting on the lid.
  • label your plates with your name.
  • Switch/turn on the bunsen burner.
  • Label three plates ‘before’ (T1) ‘after-with soap’ (S1) and ‘after-hydroalcoholic gel’ (A1)  on the underside of each plate, using a marker pen. Add your names. When turning a plate upside down, keep the lid pressed down to avoid it falling off.
  • Place the agar plates on the table (the correct way up) and remove the lid of the plate marked ‘T1’.
  • Press your fingers firmly onto the agar and then remove them. 
  • Replace the lid and clean your hands using soap. Dry them well using paper towels. 
  • Repeat the process for the agar plate marked ‘after-with soap’ and ‘after-with hydroalcoholic gel’, pressing your fingers firmly onto the agar. 
  • Replace the lid. 

How to handrub or to handwash? -from WHO

WASH HANDS WHEN VISIBLY SOILED! OTHERWISE, USE HANDRUB Duration of the entire procedure: 40-60 seconds

What do you have to do in the next step?

It’s next week !

 Compare your ‘before’ (T1) and ‘after’ (S1 and A1) handprints. 

  • Count the dots on each plate to estimate the number of bacterial colonies. Record this in a classroom table and compare your results. 
  • Why do some plates have more growth than others? 
  • What does this tell you about your hand hygiene, or the hygiene of your peers? 

 To conclude answer this quiz: 

[mtouchquiz 15]

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