CASE 2

A 24-year-old man college student presents with severe diarrhea and abdominal cramps, both of which appeared quite suddenly the day before he comes to your office for advice. He is not experiencing vomiting or nausea. His diarrhea is watery and, on gross examination, does not appear to be bloody. Vital signs are T = 37.2 C, P = 80, R = 18, BP = 120/85 mm Hg. The physical examination is unremarkable. A stool smear is prepared and examined microscopically, but there is no visible evidence for the presence of red blood cells or leukocytes in this specimen. Protozoan cysts or ova are not seen either. On taking the patient's history, you find out that he returned from a short trip to Mexico the day before his symptoms suddenly appeared. He says that he only ate thoroughly cooked food and only drank bottled soft drinks or beer during his trip. However, it was very hot, so he always asked that his soft drinks be served on ice.

Question 2.1: What is your preliminary diagnosis?

Question 2.2: What tests can you do to narrow the diagnosis?

Question 2.3: What is most likely causative agent?

Question 2.4: How does this causative agent produce disease?

Question 2.5: How is this disease acquired?

Question 2.6: How should this case be treated?

CASE 3

Three second-year medical students eat at a local Chinese restaurant that is perhaps better known for its low prices than the quality of its cuisine. Their lunch consists of hot and sour soup, spring rolls, fried rice, and three other Chinese entrees. The servings are plentiful, so the left-over fried rice and two of the entrees are taken back to their apartment and stored in their refrigerator. The students decide to reheat the food and have it for lunch two days after bringing it home. Two hours later - ironically right in the middle of their medical microbiology class - all three students are overcome with an urge to vomit and quickly excuse themselves from class. A bout of severe nausea, vomiting, and abdominal cramps follows, but only one of them experiences diarrhea (which is relatively mild). Being highly inquisitive and dedicated medical students who always like to practice their diagnostic skills, they check each other's vital signs, which turn out to be normal. The stool produced by the one student to experience mild diarrhea is watery, with no visible signs of blood or mucus. The symptoms all three victims subside within 10 hours, without treatment and without noticeable sequelae. None of the students have traveled outside of the city in which their university is located in the past six months. The reheated Chinese food is the only meal at which they all ate the same things since their lunch at the Chinese restaurant itself.

Question 3.1: How did this disease incident come about?

Question 3.2: What is the most likely causative agent?

Question 3.3: How does this causative agent produce disease?

Question 3.4: Does this causative agent produce any other forms of GI disease?

Question 3.5: How should this disease be treated?

CASE 4

An 81-year-old man is hospitalized with a history of fevers (38.6 C) for the preceding five days. Because of confusion and inability to care for himself, he has resided in a local nursing home for the past three years. However, he had been able to dress himself and move about the wards until a week before his hospital admission, when he complained of weakness and could not get out of bed. He had not experienced any recent illness, except for a urinary tract infection that occurred four weeks ago, for which he was treated with a ten-day course of ampicillin.

On physical examination, the patient is resting comfortably in bed but appears confused and rather unhappy about his change of surroundings. His temperature is 39 C, but his other vital signs are normal. There are no localized physical findings and the abdominal examination is unremarkable.

The next morning, the house staff and attending physician are pondering diagnostic possibilities at the patient's bedside when a nurse informs them that the patient passed two loose bowel movements during the night. Indeed, the attending physician's olfaction, perhaps heightened by the new information, now recognizes the occurrence of another such event, most likely triggered by deep palpation of the patient's abdomen. The attending physician calls the patient's nursing home and learns that none of the other residents have reported symptoms like those experienced by this patient.

Question 4.1: What is your preliminary diagnosis?

Question 4.2: What tests should you do?

Question 4.3: Where did the causative agent come from?

Question 4.4: What was the role of antibiotics in this case?

Question 4.5: How does this causative agent produce disease?

Question 4.6: How can this case be treated?

CASE 5

A group of FSU medical students goes to New Orleans for the weekend to celebrate after a big midterm exam. On Saturday evening, they all eat at a seafood restaurant in the French Quarter that might be considered by some to be a bit on the seedy side. The group enjoys a variety of shellfish and other local delicacies, along with the customary ethanol-containing supplements. The next morning, they head back to Tallahassee. Somewhere near Mobile, Alabama, several of them begin to feel a really urgent need for a rest area with working toilet facilities (inconvenient timing to say the least, but microbes wait for no one). Within the next hour, everyone is enjoying an explosive watery diarrhea, vomiting, nausea, abdominal cramps, and headaches. When they finally get to Tallahassee (after numerous intermediate stops), they are still experiencing intense symptoms, so they go to their student clinic. Vital signs are normal, except for one student (out of five) that has a low-grade fever. There are no gross signs of blood or mucus in the stool specimens. Microscopic examination of these specimens fails to detect protozoan cysts or ova.

Question 5.1: What is your preliminary diagnosis?

Question 5.2: What tests should be done to resolve this case?

Question 5.3: How does the causative agent get into food?

Question 5.4: How does the causative agent produce disease?

Question 5.5: What other diseases does this causative agent produce?

Question 5.6: How should the students be treated?

CASE 6

A family of five (with children aged 3, 4, and 5) decide to stop at their favorite fast-food restaurant for lunch. Everyone orders a chicken sandwich, with French fries and a large soft drink. The mother notices that the chicken filet in her sandwich is a tad pink in the middle and is tempted to take the sandwiches back to the counter. However, the children are quite hungry and were beginning to fuss in the car before the family stopped, so they are likely to throw a major tantrum if there is another delay. The mother wants to avoid this. Besides, her sandwich tastes OK, so she decides that she's just worrying about nothing.

The next day, the mother and two of the children begin to experience fever, headaches, myalgias, and general malaise. They do not seek medical attention because the symptoms are not all that severe. However, the symptoms persist for another day, when all three victims start to experience watery diarrhea, abdominal cramps, and continued fever. By the next morning they have each had about 10 bowel movements and it is apparent that additional movements are on the way, so they immediately go to their family physician. On examination, their vital signs are normal, except for fevers ranging from 38-38.5ºC. The physical examination is generally unremarkable, except that the two children are showing signs of mild dehydration. Smears of stool specimens are examined microscopically and found to contain fresh blood and PMNs (especially obvious in the specimens from the two children). There are no signs of protozoan cysts or ova. The mother relates her concerns about the chicken sandwiches but also dismisses them because only three family members are ill.

Question 6.1: What is your preliminary diagnosis?

Question 6.2: What tests should be performed?

Question 6.3: How does the lab detect and identify this causative agent?

Question 6.4: How does this causative agent produce diarrhea?

Question 6.5: What is the epidemiology of this disease?

Question 6.6: Why did only there of the family members become ill?

Question 6.7: How should these cases be treated?

CASE 7

Mr. Wilson, a 37-year-old man, decides to take his two children (Steven, age 5, and Linda, age 12) to Sweden to visit his parents, who are dairy farmers living just outside the town of Malmö. The children enjoy helping their grandparents care for the numerous domestic animals on the farm and love the home-cured meat and fresh raw milk served to them. Their father, on the other hand, is not a big fan of animals, raw milk, or home-cured meats, so he avoids them all whenever possible. Everything is fine until both children become ill 9 days after the family's arrival in Sweden. Steven develops a watery, mucoid diarrhea with occasional flecks of blood, a low-grade fever, and a diffuse abdominal pain, all of which resolve spontaneously after 4 days. Linda's episode begins in a similar fashion, but worsens after 3 days, when her pain localizes in the right lower quadrant and becomes associated with high fever and leukocytosis. She is brought to the hospital, where a tentative diagnosis of acute appendicitis is made. During surgery her appendix is found to be normal, but the terminal ileum is inflamed, with many enlarged mesenteric lymph nodes. Stool cultures were done when Linda was admitted, but they were incubated at 25(C for several days before culturing. By the time the lab reports its results, Linda has made a nearly complete recovery.

Question 7.1: What do you think the lab reported?

Question 7.2: How did the children acquire their infections?

Question 7.3: How does this causative agent produce disease?

Question 7.4: What complications may be associated with this disease?

Question 7.5: Who is most susceptible to this disease?

Question 7.6: How can this disease be treated?