How do you test for bacteria and acctually find how much of it is on a surface?

science fair. i cant find much about it on any search engines. if you have any past experiance in something like this i would love to hear about it. thanks for the help!





xx kathryn

How do you test for bacteria and acctually find how much of it is on a surface?
My son did a science fair project like this. We bought agar plates with LB agar from Carolina Biological Supply. It is difficult to get a quantative (exact) measure because you have to sample the surface and transfer the bacteria to the agar. After you innoculate the agar you wait until you can count the colonies, and that is your measure. We got the kit with an antibiotic so we could look for antibiotic resistant bacteria and molds. Also we grew a second and third generation from a single colony but we had different amounts of the antibiotic. Search anitbiotic resistance and science fair.
Reply:They generally take a swab of the inside of a person's mouth .. and place it on a special petre dish. After some time goes by, they place it under a microscope and look for the bacteria they were testing for. Good Luck! :)
Reply:http://www.freesciencefairproject.com/bi...


http://www-micro.msb.le.ac.uk/labwork/ba...


http://www.sd281.k12.id.us/Schools/Lena/...
Reply:You need sterile swabs


use a sheet of plastic cut a hole in it 1 inch by 1 inch square


wipe the top of the plastic with alcohol or betadine allow to dry.


place your template on top of the surface to swab.


Use the same method each surface (up and down X # of time to cover the area)


Also use an unrubbed swab as a negative control (be sure to crack the vial prior to innnoculating plate. (see later instructions)


You will also require blood agar plates from a science store, school, or hospital.


To innoculate your plates get your science teacher (if they know to show you) others that will know are college microbiology lab instructors, or the micro dept. at your local hospital (We are generally willing to help if the time table is not to cramped)


They can be incubated at home under a lab or in a CO2 incubator (hospital for best results).


I would recommend rubbing each surface (different areas) 4 or5


times (use a different swab for each rub)to get the best results(pictures). Be sure that each different surface is placed at the top of the stack at least once and so on to eliminate postional error in the experiment. An easy way to label the plates from 3 surface types + negative control would be #surface- # postion (this equal the rub number) example 1-1 would be the first surface - tbottom position in the stack (and first rub) ( stack postions are 1-4 bottom to top) 1-2 would be the first surface second position postion from bottom in the stack and second rub.


To take pictures use a digital camera, you may have to experiment with the light- I've had best luck with high light low flash dark backgound.


Also for your swabs the best would be prepacked micro swabs with a saline or media contianing cylinder - same sources- after rubbing place the swab back into the contianer and crack the cylinder. FOR BEST RESULTS THIS IS IMPORTANT! get instructions on this if you are not sure. Good luck