Australia's Science Forum

Some of our students wish to do the antiobiotic ring and disinfectant pracs. Not having done these before I have consulted past posts and have a fair idea of what we need to do. Just a couple of questions though.

1. Purchasing bacterial cultures, I have looked at Southern Biol and see they have "slopes" and "broths" I think I would need to buy the "broth"??? , can someone explain the difference please.
2. When I make nutrient agar, do I have to sterilise this before adding to petri dishes (we have sterile, plastic dishes)
3. Would the use of sterile swabs be ok to spread the bacterial culture on the plates

Has anyone used the petrifilm plates available from southern biol and if so with what success??

Thanks everyone and any more hints to help me with this would be appreciated

Hi Pilar, Please do a search on Agar Plates, I now use a Microwave to sterilise my agar plates, an idea pick up from this site.

Pilar, slopes are vials with agar in them that has set on an angle, to provide a greater surface area within a contained system, ie the vial. No use to you at all for this expt.

QML actually gives me agar plates for free, since we only use maybe 50 at a time, compared to the 1000's a week they use. Then they dispose of them afterwards. Try asking your local QML outlet.

Cheers, K

Yes broth is the one.
I have sterilised in the microwave however I prefer a pressure cooker or autoclave...15 mins at 15 psi.
Sterile swabs are great as well you can use inoculating loops.
When you are sterilising the agar you can wrap some cotton buds in foil and put them in the pressure cooker and you have sterile swabs.

Hi,
You can use 20gm of pepercorn in 100ml of water put in the incubator batilius subtillis is the bacteria that grows it is safe for you and children to use and can be obtained from the supermarket. this bacteria growes on N/A agar. If you use filter paper and a hole punch you can make disks soak them in disinfectant and placethem on the ager plate this work just as well as anibiotic disk and half the price.

There is a good paper called "Microbiology Safety Considerations" on Southern Biological's webpage (http://www.southernbiological.com) under Microbiological Specimens. It explains the use of broths and how to spread a lawn plus many other useful things about how schools can do micro safely with general school equipment.

pkij wrote:
Has anyone used the petrifilm plates available from southern biol and if so with what success??

Thanks everyone and any more hints to help me with this would be appreciated

Hi - no i have not used them but am looking into their use and if you do get any info regarding this part of your question i also would be interested in the comments