0:00 In this video, we're going to look at helicobacter pylori, the bacteria known 0:16 to cause peptic 0:18 ulcers as well as duodenal ulcers. 0:22 Helicobacter pylori is a gram-negative rod bacteria. 0:28 Here I'm drawing sort of simplified structure of the bacteria. 0:33 H-pylori have flagella, which help in motility, in moving around. 0:40 It also has DNA, which is circular within it. 0:46 Some important virulent factors that helicobacter pylori possesses include lip 0:52 opolysaccharides, 0:54 which help in adhering to cells. 0:59 Another important virulent factor H-pylori have is an enzyme on the surface 1:05 known as urease. 1:08 Now urease is very important in helicobacter pylori survival. 1:15 What urease does is that it converts urea and water to carbon dioxide and 1:23 ammonia. 1:25 This is important, and we'll soon see why. 1:29 But essentially ammonia, which is NH3, is quite basic, so it's alkaline. 1:37 And then H-pylori can also secrete some exotoxins, such as vac-A and cag-A. 1:45 Vac-A essentially causes apoptosis of cells, and then cag-A is responsible for 1:52 disrupting 1:54 the cellular integrity and structure, and also promotes inflammation. 2:01 If that doesn't all make sense, don't worry, hopefully we'll be able to 2:06 understand it after 2:07 going through this video. 2:09 So H-pylori is a common cause of peptic ulcers and duodenal ulcers. 2:13 Let's just have a look at the anatomy of the stomach briefly and the GIT. 2:18 So here we have the stomach and the ure of the duodenum, which is the first 2:21 part of the 2:22 small intestine. 2:23 The pylori sphincter here essentially is a barrier between the stomach and duod 2:29 enum. 2:30 Anyway, this stomach has a few parts to it. 2:33 The fundus, which is the top, the cardia, which is essentially the first part 2:36 where the esophagus 2:37 meets the stomach, the body, and then we have the anterm. 2:42 Now the anterm is the most important part here because the anterm is where H-p 2:46 ylori typically 2:47 resides in, and actually 50% of people have H-pylori living inside them, as 2:54 commensals, 2:56 you can say, commensal bacteria. 2:59 So zooming into the anterm, the stomach, we can see that the stomach cells are 3:03 composed 3:04 of columnar epithelial cells. 3:07 And the columnar epithelial cells, they have a between them junctions known as 3:12 tight junctions. 3:14 Above these columnar epithelial cells, we have a layer of mucus, which are 3:19 produced 3:20 by the goblet cells. 3:22 And mucus is very important because it acts as a barrier from the hydrochloric 3:27 acid layer 3:27 on top, and the hydrochloric acid is important to it in the digestion of food. 3:34 The hydrochloric acid is produced by cells known as parietal cells. 3:41 And of course above this acidic layer, we have the lumen of the stomach. 3:46 Reciding within the lumen of the stomach or just on top around here, we have 3:51 the bacteria 3:52 H-pylori, and they could be here either through an infection, or they could 3:59 just be there 4:00 normally because, as I mentioned, about 50% of people have H-pylori within 4:07 their stomach. 4:09 So just drawing this up, we can see that the pH decreases from the mucus layer 4:14 up the top. 4:16 So the acid layer, the hydrochloric acid layer is the most acidic. 4:22 So H-pylori, how does it survive in this acidic environment? 4:26 You see in the stomach, you find the chemical urea, and H-pylori can convert u 4:33 rea to carbon 4:34 dioxide and ammonia. 4:38 H-pylori can do this because it has the enzyme urease, and urease converts urea 4:43 and 4:43 water to carbon dioxide and ammonia. 4:47 And ammonia is sort of alkaline, so it sort of neutralizes the acidity there. 4:53 And therefore, the H-pylori is able to move down towards the cells of the 5:00 stomach. 5:01 And it can move down with the help of its flagella, which helps in motility. 5:07 So two things it's doing, it is using its enzyme urease to make ammonia, which 5:13 neutralizes 5:15 the acidity, and the H-pylori is using the flagella to help in moving down 5:21 towards the 5:22 stomach cells. 5:26 Once it makes contact with the stomach cells, it can adhere to the stomach 5:31 cells using lipopoly 5:33 saccharide. 5:35 And once H-pylori adheres to the stomach cells, it can secrete these dangerous 5:41 exotoxins, 5:42 such as KAG-A and VAC-A. 5:45 And as I mentioned, KAG-A disrupts cell integrity and essentially breaks down 5:51 this tight junctions 5:52 between the stomach cells. 5:55 At the same time, KAG-A stimulates the production of certain cytokines within 6:03 these cells, cytokines 6:05 such as interleukin-8. 6:08 So what does interleukin-8 do? 6:10 Well interleukin-8 is sort of like a chemokine, which attracts neutrophils into 6:16 the area. 6:17 And neutrophils are highly inflammatory and can damage essentially the stomach 6:24 tissue. 6:24 So interleukin-8 promotes inflammation. 6:28 Now we have VAC-A. 6:30 VAC-A essentially induces or causes apoptosis of the stomach cells. 6:36 So the combination of KAG-A and VAC-A causes essentially the breakage of the 6:43 stomach cells. 6:44 And this essentially allows the hydrochloric acid layer and mucous layer on top 6:50 to basically 6:51 come in. 6:52 And as the hydrochloric acid layer comes in, it will really damage and eat up 6:57 the surrounding 6:59 tissue. 7:00 And this is how the ulcer is formed. 7:05 We should be pointed out that the H-Pylori infection in the stomach, which will 7:10 promote 7:10 inflammation, will actually result in a lot more hydrochloric acid being 7:17 produced by the 7:18 parietal cells. 7:20 And this is because inflammation essentially promotes hydrochloric acid 7:24 secretion in the 7:25 stomach due to histamine, for example. 7:32 And with so much hydrochloric acid being produced by the stomach, the hydro 7:35 chloric acid can actually 7:37 enter the duodenum, which is normally basic. 7:41 And so this H-Pylori infection can result in a duodenal ulcer as well. 7:49 I hope this makes sense. 7:52 So I hope that made sense. 7:53 Now to diagnose a H-Pylori ulcer, you will use a Urea breath test. 8:04 A Urea breath test is essentially when a Urea chemical is tagged. 8:10 The carbon of the Urea chemical is tagged. 8:14 And then the person basically eats the Urea and then so the Urea sample will go 8:24 down to 8:25 the stomach where maybe the H-Pylori is. 8:29 If the H-Pylori is there, the Urea with water will be converted to carbon 8:36 dioxide and ammonia. 8:40 And then this carbon dioxide will actually have that chemical tagged on the 8:46 carbon. 8:46 The carbon dioxide will then leave the stomach to the bloodstream. 8:53 The carbon dioxide will travel up to the heart and then the heart will pump the 8:58 blood with 8:59 this chemically tagged carbon dioxide to the lungs. 9:03 And then the carbon dioxide will be exhaled out. 9:07 And so the presence of a chemically tagged carbon dioxide will indicate that it 9:15 is a 9:15 H-Pylori infection. 9:19 Other ways to diagnose a H-Pylori infection include a stool sample test. 9:25 Now to treat H-Pylori infections, you usually use proton pump inhibitors to 9:32 sort of prevent 9:33 hyper secretion of hydrochloric acid and you also use antibiotics to target the 9:42 H-Pylori. 9:44 Anyway, I hope you enjoyed this video. 9:48 Thank you for watching. 9:49 Bye.
