I’m going to demonstrate how to set up antibiotic sensitivity testing we do this when we’re in between two organisms or identifying unknowns. more than likely a similar setup is also used when we’re trying to determine antibiotic sensitivity in the kirby bauer test. the type of antibiotics that we may use when we’re in between two organisms are gonna be optochin,
Novobiocin or bacitracin. i’m using novobiocin today as the example. prefer to grow those on blood agar, which is what i’m going to use for the demonstration. you will also be using sterile cotton tip applicator. we’re going to have alcohol, we’re going to have forceps so that we can actually do this this is a cartridge that has this inside of it. these are going to be
The antibiotics discs that will be removed and applied on top of the bacteria. but first let’s talk about the application of the bacteria. remove it as it is a swab, we are not going to be flaming this. we are going to be flaming the mouth of the tube that we are going to be transferring from. we prefer to do this from broth, but we can also do it from solid. that’s what
We have here today. i’m going to flame the mouth of the tube, and i’m going to grab as much bacteria as i can with the swab. and i’m going to transfer to cover most of the surface of the blood agar. i want to make sure that i have bacterial growth all over the surface of the agar i’m going to dispose of my swab in a pipette box. so i have bacteria like this should not
Go in the trash. and i’m going to transfer the antibiotic disc aseptically by using the forceps and alcohol. the forceps, you don’t have to hold them to the flame because the alcohol is gonna burn off. i’m going to transfer a disc from the dispenser. you actually just have to pull them out. i like to tap it a little bit but you don’t have to jab it in there. i will dip
The forceps in the alcohol one more time, flame them so that they are clean for the next person that uses them. you can actually flip it for the incubation. it still will be okay, like you would do with any incubation of a plate. now after 48 hours, you will have growth on the surface and we’re gonna look for a halo or no halo around the disk. and this one has a very,
Very small halo almost nothing. appropriate way of determining, the proper way of determining if it is resistant or sensitive to the antibiotic is by measuring the diameter i’m going to use a ruler, we’re going to measure in millimeters. and for this specific antibiotic, if it is 16 millimeters or larger, it is actually considered to be, exactly considered to be resistant
To the antibiotic. and from this measurement, i can see that it’s at 19 millimeters. so that is resistant. obviously, this one is not going to be one that is going to be considered resistant because that is certainly less
Transcribed from video
Antibiotic Sensitivity (Novobiocin) By Ana Maria Valle-Rivera
