Read the text Describe the negative and positive roles that biological plausibility played in establishing causation. ►H.pylori and Peptic UlcersDuodenal ulcers and benign stomach ulcers are fre-quently referred to as peptic ulcers. Peptic ulcers areamong the digestive diseases with the highest inci-dence. Approximately 10% of the population experi-ence a peptic ulcer at some point in their life, thougha substantial proportion, perhaps a majority, are notmedically diagnosed. Peptic ulcers generally heal evenwithout prescribed treatment in 4-6 weeks. Approx-imately 1% of those with peptic ulcers experiencecomplications, with potentially life-threatening perfo-ration of the stomach or duodenum being the moreserious complications. The disease often recurs, with aprobability of recurrence in the range of 50%.For many years, peptic ulcers were believed to beexclusively the result of excess acid production dueto such factors as alcohol, aspirin, and other anti-inflammatory medications, spicy foods, and stress.The stomach and duodenum were known to be highlyacidic, and it was believed that bacteria were unable tosurvive in this high-acid environment.In the early 1980s, investigators observeda spiral-shaped bacterium, which they namedHelicobacter pylori, or H. pylori, in a number of patho-logical specimens from patients with disease of thestomach and duodenum. Most scientists doubted therelationship to disease, often concluding that the organ-ism must be a contaminant because of the belief thatbacteria could not grow in highly acidic environments.After many unsuccessful attempts, Australianresearchers Barry J. Marshall, MD, and J. Robin War-ren, MD, were able to culture the bacteria from thestomach and became convinced that the bacteria wereactually the cause of peptic ulcers. They were frus-trated in their attempts to demonstrate that H. pyloriwas the cause of the disease because of the absence ofgood animal models.To attempt to establish causation, Marshall dranka flask of the cultured bacteria. He became ill anddeveloped acute ulceration of the stomach. H. pyloriwas cultured from his ulcerations. This dramatic effortbrought attention and extensive investigations toaddress whether H. pylori is a contributory cause ofduodenal ulcers.Subsequent studies in the United States and othercountries established that H. pylori is a frequentlyoccurring organism that increases with increasingage. Overall, over 20 % of people in the United Stateshave H. pylori; that is its prevalence is over 20% in theUnited States, with a higher prevalence beginning atan early age in many developing countries, as well asJapan. In case-control studies, H. pylori was found to the time of their diagnosis.I have a strong association with duodenal ulcer,over 70% of peptic ulcer patients having H. pylori atRandomized controlled trials examined therecurrence rates of duodenal ulcers after treatmentof the bacteria with antibiotics shown to eliminateH. pylori. In one study among those randomized toplacebo, the recurrence rate was over 10 times as greadirected against H. pylori. This research led to a searchas among those randomized to antibiotic treatmentfor biological mechanisms. Extensive research estab-lished a greater understanding of the physiology ofpeptic ulcers, including identifying the production ofan enzyme by H. pylori that reduces acidity and thusfacilitates its growth in an acid environment.New tests demonstrated that H. pylori is associ-ated with the great majority of duodenal ulcers;withamongoutpatients. Randomized controlled trials and exten-sive clinical follow-up established the effectivenessand relative safety of antibiotic treatments of H.pylori.These investigations led to evidence-based recommen-dations for routine testing for H. pylori among outpa-tients diagnosed with peptic ulcers and treatment ofH. pylori with antibiotics when it was detected.300In the US diet can.

In order to examine the role of biological plausibility in demonstrating causation, the association…

Answered: H. pylori. In one study among those…