Helicobacter pylori (H. pylori)

Helicobacter pylori is a bacterium that infects the mucus lining of the stomach and duodenum. During my undergraduate research, our sister lab was working to characterize the flagella of this little guy. We discussed H. Pylori in my Cell Bio course last week, and given its importance, I thought this was an imporant bacteria for all to know about.

Distilled from Wikipedia and Lecture Notes: Found in up to 50% of the world’s population, making it the most common infectious disease worldwide, a main cause of peptic ulcers and stomach cancer. H. pylori is an unusual bacteria — the only known bacteria that can cause cancer and one of the only bacteria that can survive in the acidic environment of the stomach. The corkscrew-shaped bacteria drills itself into the stomach lining and, while nourishing itself, reduces the stomach’s ability to produce acid. This often leads to pepticulcers, non-Hodgkins lymphoma of the stomach and gastricadenocarcinoma. Now usually can be eradicated with a combination of proton pump inhibitors and antibiotics.

In their original paper, Robin Warren and Barry Marshall (Australians who studied the bug) contended that most stomach ulcers and gastritis were caused by colonization with this bacterium, not by stress or spicy food as had been assumed before. The medical community was slow to recognize the role of this bacterium in stomach ulcers and gastritis, believing that no bacterium could survive for long in the acidic environment of the stomach. The community began to come around after further studies were done, including one in which Marshall drank a Petri dish of H. pylori, developed gastritis, and the bacteria were recovered from his stomach lining, thereby satisfying three out of the four Koch’s postulates.

Infection may be symptomatic or asymptomatic (without visible ill effects). It is estimated that up to 70% of infection is asymptomatic. The bacteria have been isolated from feces, saliva and dental plaque of infected patients, which suggests gastro-oral or fecal-oral as possible transmission routes. Infection rates vary from nation to nation – the West (Western Europe, North America, Australasia) having rates around 25% and much higher in the Third World. In the latter, it is common, probably due to poor sanitary conditions, to find infections in children. In the United States, infection is primarily in the older generations and the poorest. This is largely attributed to higher hygiene standards and widespread use of antibiotics. However, antibiotic resistance is appearing in H. pylori . It is widely believed that in the absence of treatment, H. pylori infection–once established in its gastric niche–persists for life.