Testing the effects of various disinfectants on the growth of - PowerPoint Presentation

Slide1

Testing the effects of various disinfectants on the growth of E. coli

Pam Stewart

Slide2

objectives

Compare

the effects of different products that claim to kill bacteria

Design a controlled experiment

Plan a methodology using appropriate tools to gather precise and accurate data

Determine if data obtained was valid and reliable

Compose and defend a conclusion based on data obtained from a controlled experiment

Publish results of a controlled

experiment

Learn sterile handling techniques for bacteria growth

Successful cultivation of bacteria

Slide3

Previous Learning

Students will apply previous learning to design and complete the experiment

Scientific Method

Graphing

Slide4

Journaling for a lab

Research question / Purpose

Background

Independent variable

Dependent Variable

Hypothesis

Create the following sections w/ notes for tomorrow’s lab:

Slide5

Observation

Everyone in the family contracts severe food – poisoning one night after dinner.

Slide6

First Question

What caused it?

Mom remembers cutting up the raw beef on the same cutting board she chopped vegetables on.

She only rinsed the cutting board with water between uses

Slide7

Research Question

Which product is best to clean/sanitize the cutting board?

Determine the best product to eliminate the E. coli from the cutting board

Research Purpose

Slide8

background

E. coli

is most commonly found in the intestines of humans and other warm-blooded animals

Transmitted most through raw/uncooked meat and surfaces

Prokaryote: one-celled organism w/ no nucleus

Slide9

Background research

They

live in mixed populations almost everywhere.  

Observing

one isolated bacterial specimen not contaminated with other microorganisms is not representative of the real world

Slide10

What does e. coli look like growing on nutrient agar?

Slide11

What will it look like if the product is effective?

Zone of Inhibition

Slide12

Design a controlled experiment

Independent variable

Dependent variable

The various products that claim to kill bacteria (E. coli)

The growth of E. coli – determined by measuring the zone of inhibition around each product disk

Slide13

Bleach

kills some of the most dangerous bacteria,  including staphylococcus, streptococcus, E. coli and salmonella – as well as viruses like the flu and the common cold. Harmful to respiratory tract and should only be used in a diluted form

Soap

There is a common misconception that antibacterial soap, in particular, is effective in eradicating all germs. Although antibacterial soap may kill some bacteria, it is no more effective in doing so than regular soap, and does nothing to fight viruses like colds or the flu.

Anything w/

triclosan

Cleans no better than regular soap but has been found to be disruptive to human endocrine system

Ammonia based products

Although it may be a more eco-friendly cleaning solution than chemical-based products,  ammonia is not registered as a disinfectant by the Environmental Protection Agency (EPA). Although ammonia might kill salmonella and E. coli, it is not an effective defense against dangerous staphylococcus bacteria.

Alcohol-based sanitizers

 claim to prevent infection from MRSA, salmonella, E. coli, the flu, or other bacteria and viruses, but the claims aren’t supported by the FDA. The Centers for Disease Control and Prevention (CDC) also warns that these products are largely 

ineffective against the norovirus

. Some hand sanitizers may also contain

triclosan

.

vinegar

does not kill dangerous bacteria like staphylococcus.

Baking soda

ineffective against most bacteria, including salmonella, E. coli. and staphylococcus. 

Slide14

Choose 6

With your table group, determine which products you wish to test.

We will vote and determine which 6 we wish to test

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Hypothesis

Write your group’s hypothesis

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Constants / Controlled variables

What do we need to keep consistent to prevent confounding variables?

Type of agar

Same strain of

E. coli

Test same products

Same growth time

Same methodology

Slide17

Day 2 – Lab daybell work

Prepare yourselves to conduct a lab

Hair pulled back

No loose or dangling clothing / jewelry

Pants

Closed toe shoes

Slide18

objectives

Compare

the effects of different products that claim to kill bacteria

Design a controlled experiment

Plan a methodology using appropriate tools to gather precise and accurate data

Determine if data obtained was valid and reliable

Compose and defend a conclusion based on data obtained from a controlled experiment

Publish results of a controlled

experiment

Learn sterile handling techniques for bacteria growth

Successful cultivation of bacteria

Slide19

Materials Manager:

1 – agar plate

1 – sterile disposable pipet

1

– sterile

swab

1 – paper towel

1 - Box of paper disks (to

soak

w/ products)

1 – disinfecting wipe (to clean lab table)

1 – forceps

1 - sharpie

Slide20

Lab Technician

Get on a pair of gloves *

Obtain 1

– small yellow tube (E. coli)

* Only the lab tech needs to wear gloves

Slide21

Recorder - procedures

Always label an agar plate on the bottom of the plate!

Label the plate with your lab group’s period number and lab table number

Example: period 1, lab table 3 = 1 – 3

Slide22

Draw 6 small circles, evenly spaced and label them with a

number (1 – 6)

Create

a drawing in your lab book to represent your agar plate and label the circles the same as you did on the plate

Recorder - procedures

1

2

3

4

5

6

Slide23

Product numbers:

409

Lysol spray

Toilet bowl cleaner

vinegar

Hand sanitizer

Wet wipes

Recorder - procedures

Slide24

Quality Control - Procedures

Today’s goal is to avoid contamination!

Sanitize work station before beginning lab

Only open the agar plate lid & yellow tube lid enough to do the required procedures, then immediately close it back

Do not place agar plate lid onto desktop = contamination

Dispose of pipet and swabs in the green bucket on front lab desk

Slide25

Lab Tech - procedures

Using sterile pipet, transfer .25 mL from the E.coli broth tube onto the agar plate

Using sterile transfer swab, spread e. coli broth evenly onto the plate surface

Do this gently so as not to puncture the agar

surface

Slide26

Lab Tech - procedures

Using forceps, dip

one piece of hole-punched

paper into the product solutions being tested

Do

not place the paper over the agar until it has stopped

dripping

Dripping the product onto the agar will skew the results!

Using forceps, Place the product soaked paper onto the designated circle on the agar

Repeat for all products being tested

Slide27

Quality control - procedures

Allow 5 minutes for everything to soak into the agar

Turn agar plate upside down, then place it into the incubator

The lid should be on the bottom at this point

Everyone

Clean and sanitize work station

recorder

Record the temperature on the incubator

Slide28

Bell Work – Day 3

Write your

group’s

hypothesis as an if/then statement:

Example: If hand sanitizer most effectively kills E. coli, then the zone of inhibition around hand sanitizer will be larger than any other product’s.

Then, attempt to write it without using an if/then statement:

Put today’s

bellwork

directly into your class journal – not on an index card.

Slide29

objectives

Compare

the effects of different products that claim to kill bacteria

Design a controlled experiment

Plan a methodology using appropriate tools to gather precise and accurate data

Determine if data obtained was valid and reliable

Compose and defend a conclusion based on data obtained from a controlled experiment

Publish results of a controlled

experiment

Learn sterile handling techniques for bacteria growth

Successful cultivation of bacteria

Slide30

Lab Tech

Obtain your group’s plate from the incubator

Do not open it!

Slide31

results

Decide with your lab group if you will measure the radius or the diameter

Measure the zones for each product

You must measure in mm

Inches = 2.54 cm

2.54 cm = 25.4 mm

Share results with teacher to add to class data

Slide32

Graphing the results

Working with your table group, put the class data into graph format.

Conclusions

Using the class data, analyze whether the results obtained support or reject the hypothesis for your group.

Slide33

Bell Work – Day 4

What is bias in an experiment?

Slide34

objectives

Compare

the effects of different products that claim to kill bacteria

Design a controlled experiment

Plan a methodology using appropriate tools to gather precise and accurate data

Determine if data obtained was valid and reliable

Compose and defend a conclusion based on data obtained from a controlled experiment

Publish results of a controlled

experiment

Learn sterile handling techniques for bacteria growth

Successful cultivation of bacteria

Slide35

Each group will create a poster that contains the following information:

Research purpose or research question

Hypothesis

1 or 2 sentence methodology summary

Graph of results

Conclusion statement -

Should include an overall statement of most effective product and how that relates back to hypothesis

Acknowledge any potential errors &/or necessary improvements

Publishing the results

Slide36

Exit ticket

Did this experiment have any confounding variables? If so, what were they?