Hand washing

You will complete the lab report based on a physical lab that has already been completed. You do not need to purchase the supply list in the instructions. You will answer the lab questions based on the pictures provided.

For this lab, you will write a lab report on the report form. Note: you are REQUIRED to use this report form and enter your responses on the form in the appropriate location (after the indented a or b below the topic or question). A zero score will be entered for submissions that do not use the required report form and/or do not follow the directions.

Our skin is the first line of nonspecific immune defense. There are several forms of protection, such as lysosomes in our sweat and the natural biome on our skin. This lab focuses on our hands because we use our hands to touch objects. The microbes on the objects we touch are then introduced into our bodies by rubbing our eyes, licking fingers, rubbing or picking our nose, or through a cut in the skin. People are encouraged to wash their hands regularly to decrease the transmission of microbes from our hands.

Why are our hands such a rich environment for microbes? First, there is the structure of our skin. The outer layer, stratum corneum, is made up of dead cells. Microbes live off of the dead skin cells. The lower layers of the skin keep the microbes from entering the body.

When we consider the types of microbes on our skin, it is important to recognize there are the bacteria that normally live on your skin and the bacteria you encounter as you go through your day. The first are called resident bacteria. The bacteria you encounter throughout life that are not part of your skin’s normal microbiome are called transient bacteria. Transient bacteria are the ones you pick up as you move through the day, such as touching surfaces at different businesses you visit (e.g., door handles, tables or counters, restroom handles, etc.) and shaking hands with others. The transient bacteria are easily removed from the skin by washing hands. The resident bacteria live in deeper layers of the skin, so they are not as easily removed.

The resident bacteria do serve a purpose. They help kill off transient bacteria because they produce bacteriocins. That said, the resident bacteria can become problematic if the person has immune issues. People who have acute or chronic conditions are at greater risk for bacterial infections from the resident bacteria because their immune system is working hard to fight the other infections.

In this lab, you will learn about the importance of handwashing in controlling the amount and type of bacteria on the hands.

Materials used in the lab:

  • Seven petri dishes with nutrient agar
  • Distilled water
  • Tap water
  • Antibacterial gel
  • Hand soap
  • Paper towels
  • Hand towel – clean
  • Hand towel – used several days

Methods:

The petri dishes are marked 1 through 7 to align with the following:

  • Dirty hands
  • Rinsed with tap water
  • Antibacterial gel
  • Hand soap, no drying
  • Hand soap, dried with paper towels
  • Hand soap, dried with a hand towel used four days
  • Hand soap, dried with a clean hand towel

The following steps were taken by the experimenter. Images of the resulting plates after incubation are below.

A small amount of distilled water is poured on participant’s hands. Participant rubs hands together to spread the distilled water over the hands and between the fingers. Researcher uses a sterile swab to collect sample from the palm and back of hands, and between the fingers.

Participant rinses hands while rubbing them together using tap water. Researcher uses a sterile swab to collect sample from the palm and back of hands, and between the fingers.
Researcher sprays antibacterial gel on participant’s hands. Participant rubs hands together to spread the antibacterial gel over the hands and between the fingers. Researcher uses a sterile swab to collect sample from the palm and back of hands, and between the fingers.

Participant washes hands using soap and tap water. The participant does not dry his hands. Researcher uses a sterile swab to collect sample from the palm and back of hands, and between the fingers.

Participant washes hands using soap and tap water. He dries his hands with paper towels. A small amount of distilled water is poured onto his hands after drying and participant rubs the distilled water over the hands. Researcher uses a sterile swab to collect sample from the palm and back of hands, and between the fingers.

Participant washes hands using soap and tap water. He dries his hands with a clean cloth hand towel stored in a kitchen drawer. A small amount of distilled water is poured onto his hands after drying and participant rubs the distilled water over the hands. Researcher uses a sterile swab to collect sample from the palm and back of hands, and between the fingers.

Participant washes hands using soap and tap water. He dries his hands with cloth hand towel that has been used four days. A small amount of distilled water is poured onto his hands after drying and participant rubs the distilled water over the hands. Researcher uses a sterile swab to collect sample from the palm and back of hands, and between the fingers.

Research closes the plates and incubates them for five days until growth appears.
Images of the incubated petri dishes are in the lab report.

Complete the lab report and submit to the classroom via the SUBMIT button in the upper right corner on this page. When completed, your lab report must be a minimum of four pages. Any researched details must be identified correctly in APA 7th edition format (Links to an external site.) using citations and references.