LESSON 2.5 WORKBOOK Identifying infectious bacteria-ulcers, and what s up your nose?

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1 Helicobacter pylorii DEFINITIONS OF TERMS Peritonitis: inflammation of the peritoneum, the thin tissue that lines the inner wall of the abdomen and covers most of the abdominal organs. For a complete list of defined terms, see the Glossary. LESSON 2.5 WORKBOOK Identifying infectious bacteria-ulcers, and what s up your nose? This lesson continues to grapple with the problem of arriving at causation from correlation by looking at another infectious agent that does not perfectly fit into Koch s postulates, helicobacter pylori that is thought to cause stomach ulcers. Despite the Nobel Prize having been given to its discoverer, Koch s postulates have never been fully established for this infectious agent. Hence we can only say that helicobacter is the expected cause of ulcers. Pathophysiology of a stomach ulcer. An ulcer is a persistent wound in the epithelium of the stomach or small intestine that does not heal. Stomach (peptic) ulcers are particularly painful because of the strong acid secreted into the stomach during a meal. The stomach epithelia are normally resistant to the acid, but when they are damaged they expose parts that are acid sensitive. As a result, peptic ulcers cause the most pain during a meal. Duodenal ulcers Duodenal ulcers are found in the small intestine below the stomach. In this case eating food soothes the pain because the digested food protect the exposed damaged epithelia. In both cases, symptoms may include vomiting and in extreme cases peritonitis, which results from bacteria entering the sterile area of the abdomen through the ulcer. Up until 1982, Ulcers were thought to be caused by Fig 2.5.1: Peptic ulcers are found in the stomach, duodenal ulcers are found in the small intestine. What accounts for the differences in when you feel pain if you have an ulcer? How might an ulcer lead to peritonitis? Lesson 2.5 genetics, stress and/or diet. 1

2 DEFINITIONS OF TERMS Correlation: a connection between two things. Causation: When a change in one thing results in a change in another. For a complete list of defined terms, see the Glossary. LESSON MATERIALS Case Study: Stomach ulcers and the mysterious bug Background: Generally healthy, although a little overweight, Reg began to have problems with his digestion after work at the supermarket chain became stressful: There was some trouble over a missing piece of jewelry and the relationships between the staff became very strained. As the General Manager of the large store where it happened, I took the brunt of everyone s bad feelings. For the first time in my life, I experienced real stress. The woman whose expensive gold charm bracelet had gone missing accused a colleague of stealing. The bracelet never turned up, and both women left after a few weeks, but not before some intense bouts of recrimination and uncomfortable silences, all of which created a very bad atmosphere. Reg ignored the abdominal pain that came in the middle of the night, and began drinking a bit more than usual. Once things got back to normal at work after the two co-workers left, he expected to feel OK again, but the pain was worse than ever. I was not sleeping and I started to feel uncomfortable during the day as well. Reg said. His doctor suspected that he might have an ulcer and sent him for some tests. My brother and sister both have a history of ulcers, so I wasn t really surprised. I had never been troubled before but it puzzled me that the specialist at the hospital was so interested in my bad breath. I am famous for it and none of my grandchildren will come and sit on my knee for a cuddle, they say I am Granddad Firebreath, laughed Reg. Reg s bad breath had been with him as long as he could remember even though he had taken good care of his teeth, which were better than most men of his age. The test results revealed the Reg did indeed have an ulcer, and his blood showed high levels of antibodies to a bacterium Helicobacter pylori. Describe Reg s symptoms Lesson 2.5 2

3 How do you think the doctor confirmed that Reg had an ulcer? Stomach ulcers have been a health problem throughout history. There was some evidence from the case study that they may be an infectious disease. What is it? Would you be satisfied with this evidence as proof that stomach ulcers are an infectious diease? If you wanted to explore the possibility that stomach ulcers are caused by an infectious agent what steps would you take? Be as specific as you can. (Think about Koch s postulates: Association, Isolation, Causation, Re-isolation). Lesson 2.5 3

4 Where would you expect to find any microbes that could be culprits? How would you see them? How would you isolate the microbe? If you can t grow the microbe in culture what do you do next? Let s say you can culture the microbe, how would you know that the microbe causes the disease? Would you use a human to test this? What if the microbe does not cause disease in animal models? Lesson 2.5 4

5 Reg s Treatment: I had thought that stomach ulcers developed because of stress but I was told that over 80% are caused by a bacterial infection. I had never heard of Helicobacter pylori, but apparently people can be infected in childhood and never know it. We grew up in the South side of Chicago, it was tough and conditions were hardly luxurious. I ve probably had the infection since then, but it is only now that it has made its presence felt, explains Reg. Reg was given triple therapy with three antibiotic drugs known to clear H. pylori infections and was tested again six months later. Not only had the ulcer cleared up but, to the delight of all the family, my bad breath had gone too! says Reg. Tests showed that Reg was clear of the bacterial infection and that his ulcer had healed well. Reg s story included a stressful experience at work that he thought caused his ulcer. Do you think that his stress contributed to the ulcer? If bacteria caused his condition why would stress make it worse? Lesson 2.5 5