tailieunhanh - Chapter 144. Helicobacter pylori Infections

Helicobacter pylori, which persistently colonizes the stomachs of ~50% of the world's human population, is the main risk factor for peptic ulceration (Chap. 287) as well as for gastric adenocarcinoma and gastric MALT (mucosa-associated lymphoid tissue) lymphoma (Chap. 87). Treatment for H. pylori has revolutionized the management of peptic ulcer disease, providing a permanent cure in many cases. The prevention of H. pylori colonization could potentially represent primary prevention of gastric malignancy and peptic ulceration. However, controversial but increasing evidence indicates that H. pylori may in fact offer some protection against recently emergent diseases—most notably gastroesophageal reflux disease (GERD). | Chapter 144. Helicobacter pylori Infections Helicobacter pylori which persistently colonizes the stomachs of 50 of the world s human population is the main risk factor for peptic ulceration Chap. 287 as well as for gastric adenocarcinoma and gastric MALT mucosa-associated lymphoid tissue lymphoma Chap. 87 . Treatment for H. pylori has revolutionized the management of peptic ulcer disease providing a permanent cure in many cases. The prevention of H. pylori colonization could potentially represent primary prevention of gastric malignancy and peptic ulceration. However controversial but increasing evidence indicates that H. pylori may in fact offer some protection against recently emergent diseases most notably gastroesophageal reflux disease GERD and its complications . esophageal adenocarcinoma . Thus clearance of H. pylori from human populations may not be without negative repercussions. Etiologic Agent H. pylori is a gram-negative bacillus that has naturally colonized humans for at least tens of thousands of years. It is noninvasive and lives in gastric mucus with a small proportion of the bacteria adherent to the mucosa. Its spiral shape and flagella render H. pylori motile in the mucus environment. This organism has several acid-resistance mechanisms most notably a highly expressed urease that catalyzes urea hydrolysis to produce buffering ammonia. H. pylori is microaerophilic requiring low levels of oxygen is slow-growing and requires complex growth media in vitro. Publication of several complete genomic sequences of H. pylori since 1997 has led to significant advances in the understanding of the organism s biology. A very small proportion of gastric Helicobacter infections are due to species other than H. pylori which probably are acquired most often as zoonoses. Whether these non-pylori gastric helicobacters cause disease remains controversial. In immunocompromised hosts several nongastric intestinal Helicobacter species can cause disease with clinical .