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Inoculating a Blood Agar Plate and adding a Taxo A Bacitracin Disc

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This video lesson demonstrates how to inoculate a Blood Agar plate and add a Taxo A (bacitracin) disc. This is used to identify Group A Beta Streptococci (Streptococcus pyogenes).

In this video lesson we’re going to learn how to streak a blood agar plate and so a disc containing the antibiotic bacitracin on the plate this is the classic test for identifying streptococcus pyogenes the bacterium that causes strep throat so the first thing we have to do is streak our blood agar plate for isolation so we start by removing the unknown bacterium so

We sterilize our inoculating loop for 10 seconds in the back tone sin rater first then we take our culture of unknown we’re going to stick it in the auger to cool and scrape off a little bit of the bacteria now we’re going to spread that out over sector one of our blood agar plate by dragging it back and forth after we cover sector one we sterilize the inoculating

Loop for ten seconds we stick the loop in the edge of the auger to cool now we’re going to rotate the plate so the bacteria in sector 1 that are 12 o’clock are sitting at 9 o’clock we’ll take our sterile inoculating loop and drag that through sector 1 2 or 3 times and spread that out over sector 2 without dragging it through after the first couple of times then again

We sterilize the inoculating loop stick it in the auger to cool at the very edge we rotate the plates of the bacteria in sector 2 are now sitting at 9 o’clock and we take our sterile inoculating loop we drag that through sector 2 a couple of times and spread that out over sector 3 being careful not to touch sector 1 and since this is blood agar once we’ve streaked

The plate for isolation we stab the agar a couple of times in each of the three growth areas so that some bacteria grow under the auger and that allows us to see more hemolysis faster especially since certain hema license are inactivated by oxygen so once we’ve spread the bacteria in sector 3 we just go straight to the agar to a couple of stabs in each of the three

Growth areas and we’ve streaked the plate for inoculation we can now sterilize the inoculating loop and now ready to place on the tax oh a or bacitracin disk and it’s called an a disk because it’s used to identify group a made a strip which is streptococcus pyogenes we’re going to place the tech so a disc in the centre of sector two so we raise the lid this is

Designed so that when we push down on the handle here that will be ejected discs so we hold that over long you want it in sector two we gently push until the disc comes out then we’re going to take our inoculating loop and use that to touch the disc so it makes good contact with the auger and at that point the blood agar plate with the a disc can be incubated upside down at 37 degrees

Transcribed from video
Inoculating a Blood Agar Plate and adding a Taxo A Bacitracin Disc By Dr. Gary Kaiser