 Welcome back to our meds smarter lecture series where we're taking a smarter approach to preparing future physician Before we get started if you'll take just a quick minute and click that like button and also Subscribe and turn the bell on so that you'll be notified when we post new videos. Let's talk about another gram-positive organism in corner bacterium diphtheria Corner bacterium diphtheria in and of itself is a gram-positive rod that occurs in angular Arrangements now. What does an angular arrangement mean? Well, you can see in this picture here that they are attached at the ends And they're in angles so this angle here is about of a 60-degree angle And that's how you're gonna see these under a microscope. These are transmitted to other human beings via respiratory droplets So we have quite a few organisms that are transferred via respiratory droplets. This causes diphtheria All right, so diphtheria is the disease caused by a corner bacterium diphtheria How it does this is via an endotoxin and that endotoxin is encoded by a beta-prophage That's something to remember about corner bacterium diphtheria is it is a beta-prophage exotoxin the exotoxin inhibits protein synthesis by ADP ribosylation of the EF2 factor which is elongation factor 2 and This leads to possible necrosis in the pharynx cardiac muscle and CNS tissue So this necrosis is important because this is where we get the diphtheria symptoms So we can see pseudomembranous pharyngitis Which is a necrosis of the pharynx here and as well as showing some lymph adenopathy alongside of it This toxin can then be disseminated throughout the body causing myocarditis arrhythmias and neuropathies and How do we prevent this? Well, we can give a toxoid vaccine that toxoid goes in and helps prevent diphtheria from occurring To diagnose corneal bacterium diphtheria We diagnose this by seeing gram positive rods with a metachromatic granules now the metachromatic granules are also known as volatine granules a volatine granule or a metachromatic granule is just a intracytoplasmic storage form of Some inorganic polyphosphate and it gives a metachromatic effect Which basically means when we stain this with methylene blue the granules will appear red So staining it with blue makes them appear red and then also a diagnostic criteria for corneobacterium diphtheria is a positive elic test which tests for the toxin what we do here is we take a strip of paper that has the Antitoxin for diphtheria, and we put it into the auger just underneath the surface and what happens here is we streak the surface with our diphtheria and We see some lines that will occur on the paper because the antitoxin and the exotoxin of Diphtheria will react with each other and produce some precipitin lines along that filter paper that we've put underneath the auger So if we see those lines on that filter paper that is considered to be a positive elic test for that toxin You can see here in this picture. This is what Corneobacterium diphtheria looks like on the on a leg of a patient Just a very big necrotic lesion there So let's break down corneobacterium specifically. We know bacteria means but the corne that stands for club shaped The corne is club shaped and that's where we have our metachromatic granules that we see on the waffler media We also see black colonies under specific cysteine telluride auger and we treat Corneobacterium diphtheria with an antibiotic and we can also give a diphtheria antitoxin That will help reduce the effects of that exotoxin So here's a good way to help remember Corneobacterium diphtheria is using ABCDEFG. So A is your ADP rib oscillation We talked about that is how the exotoxin inhibits our protein synthesis and specifically it's ribosilating the elongation factor 2 which we'll get to that's going to be our E in ABCDEFG the beta prophase This is what the exotoxin is encoded by and then C and D is your corneobacterium diphtheria E as we've mentioned already is our elongation factor 2 that elongation factor 2 is what is inhibiting protein synthesis via the ADP rib oscillation. So these two are connected and Then G is our granules or our metachromatic granules If you found this material helpful for your studying, please like and consider subscribing to the channel Also share this video so that more people can benefit from it like you have