This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Microbiology
H. pylori is found in? 
Select and explain. 
A. Epithelial lining, B. Mucous layer, C. Lamina propria, D. Sub mucosa
B: Mucous layer
Answer: B: Mucous layer 
Explanation: Mucous layer REF: Jawett's 24' edition chapter 18 H pylori grows optimally at a pH of 6.0-7.0 and would be killed or not grow at the pH within the gastric lumen. Gastric mucus is relatively impermeable to acid and has a strong buffering capacity. On the lumen side of the mucus, the pH is low (1.0-2.0) while on the epithelial side the pH is about 7.4 H pylori is found deep in the mucous layer near the epithelial surface where physiologic pH is present. H pylori also produce a protease that modifies the gastric mucus and fuher reduces the ability of acid to diffuse through the mucus. H pylori produce potent urease activity, which yields production of ammonia and fuher buffering of acid. The mechanisms by which H pylori causes' mucosal inflammation and damage are not well defined but probably involve both bacterial and host factors. The bacteria invade the epithelial cell surface to a limited degree