hey everybody dr. Rowe here this video were going to talk about the kirby Bauer dis diffusion method one of the one of the most important labs that are done in a microbiology lab and obviously very important clinically as well so so here you see an example of the Kirby dowered distaff Eugene method so what you do is you create I love the term you you put a confluent lawn of organisms on a plate no no that means you're gonna cover the entire plate usually when you as students are are working with plates we're doing streak plates or pour plates we're trying to spread bacteria out and and separate them in this case you want to cover the entire plate with microbes so you spread a confluent lawn what I have students do is rather than using a wire loop they'll use cotton tip applicators and coat the entire surface of a plate with organisms now we use known organism samples that I make for them obviously in the real world clinically you could you would cover this plate with pathogens isolated from human from from a sick person so you cover you cover the entire plate with organisms then you put these discs that have known quantities of antimicrobials antibiotics on them and then you actually will incubate them and come back and look we're looking for these clear areas what are known as zones of inhibition so how large of an area around one of these paper discs is there is there no microbial growth and that will tell us a few things but just so you know just having a zone of inhibition isn't it doesn't tell us everything we need to know and the size matters so first of all we have to standardize this that's why we use we use special plates I have another image I can show you how kind of bounce back and forth we use special plates you see the MH there they're called Mueller Hinton plates and even the thickness of the plate matters so we use double thickness Muller hidden agar plates and then these zones of inhibition once you actually measure them we have to compare them to these these charts so I we have data tables that say for this antibiotic and this organism this with this size of zone of inhibition means that it's sensitive and it works if it's smaller than that it might be intermediate which means it sort of works or it might be resistant so there's tons of factors that go into play here so just looking at a plate and saying this zone efficient is the biggest this means it's the one that works the best is not actually true it also won't tell you if it kills the microbes if it's if it's bactericidal or or just inhibits their growth bacteriostatic soso certainly there are some weaknesses here but I find it's a it's a pretty effective laboratory tool to teach students how some antibiotics will work better than others here we see just as an example of you know these same four antibiotics clearly work a lot better against Staphylococcus aureus than they do against them Pseudomonas so that's not that's not uncommon generally in the lab we will use staph aureus will use e.coli will use Pseudomonas and maybe Proteus vulgaris just kind of a random assortment but this is this is pretty common here so alright so that is the Kirby Bower dis diffusion method and how it can be used in a laboratory as well as the clinical setting I hope this helps have a wonderful day be blessed