Expert: Dr. Henry Boyter, Jr. - 10/18/2006

Question
My daughter's (9th grade)project involves finding out the lenght of time that it takes for a toothbrush to get bacteria once it's used a first time.  Will she need to go to a lab to check this (petri dish w/ growth medium) or can she do this at home? if so, what type of materials will she need (besides the tootbrush)?

Thank you for your cooperation.

Answer
She will need a lab.  By the time the bacteria are visible, they will have been on the toothbrush for a while.  I'm not an expert in this area, but my guess is that the toothbrush bristles are not a good media for visible bacteria.  You may talk to a lab and see if they will give you some media to try at home. One point, there are bacteria on the toothbrush as soon as you use it.  They are transferred from your mouth.  She needs to frame her question to the specifc source of bacteria she is interested in checking (airborne, water growth, etc). Her teacher should be able to help her with that.