n Case 1: At the age of 63 years, Mr. O. had an operation to remove a tumor that obstructed his stomach. The surgeon resected part of stomach and connected the remainder part with the jejunum, bypassing the un-resected duodenum. Two years later, Mr. O. developed chronic diarrhea, and his weight dropped from 139 to 97 pounds. On examination he was extremely thin, fatigued with short of breath and numbness and tingling in his hands and feet.

N Laboratory tests showed a severe anemia with large red blood cells (ovalocytes) and hypersegmented neutrophils. Serum levels of Vitamin A, and Carotene were depressed. Serum Vitamin B 12 was undetectable. Specific test for fat contents in stool analysis revealed steatorrhea CFU of Bacteroides fragilis and 10 6 E.coli CFU per mL were isolated from small bowel specimens.

N 1- What is your diagnosis? 2- What is the cause of this abnormality? 3-How can you confirm your answer? 4-What is the underlying cause of the numbness and tingling experienced by Mr. O? 5- What is the mechanism of the diarrhea that established due to this conditions?

n Case 2: Mr. R., an 85-year-old resident of a nursing home was visited by E., his 3-year-old granddaughter. The two shared a fast-food hamburger for lunch. One day later, Mr. R had a watery diarrhea every 15 to 30 minutes, initially with small amount of visible blood. Later that day, bright red stools consisting of pure blood appeared. Mr. R was hospitalized and a barium enema revealed edema of the ascending and transverse colon.

n Routine stool cultures were negative for Salmonella and Shigella. However, Sorbitol non-fermenting E. coli was identified by Lab as a serotype O157:H7. One day after Mr. R fell ill, E. developed watery bloody diarrhea that increased over the next 2 days. When E. began to vomit and her urine output appeared to diminish, her parents took her to the pediatrician. The laboratory reported a significant decrease in platelets and red blood cells, many of which looked abnormal. Serum creatinine level was slightly elevated.

N The patient was treated with intravenous fluids and no antibiotics were given. No hypertension developed and she was discharged 1 week later due to improvement in the blood count and kidney function test. 1-What is the likely source of infection? 2-Diagnosis of E. case. 3-How can you confirm this diagnosis? 4-By which mechanism does the responsible etiological agent cause these diseases in Mr. R and E case? 5-What are the principle therapeutic concerns in such case.

N Case 3: Mr. L., a 23-year-old patient came to the emergency department because of jaundice. For several days he had felt increasingly weak, nauseated, and feverish and had pain on the right side of his abdomen. He reported that he had experimented with a variety of oral and injectable drugs. The emergency physician suspected that Mr. L. had acute hepatitis. The laboratory reported increased SGPT, Alkaline phosphatase, and total and direct bilirubin.

N HBsAg was detected in serum. Anti-HBsAg Antibodies were negative. 1-By what route might Mr. L. have become infected? 2-What is the period of Hepatitis B infection seen in this case? 3- How can you confirm your answer? 4-What follow-up tests will be required to determine his long-term prognosis? 5-What advice can Mr. L be given to avoid further transmission of infection.

N Case 4: An elderly patient is placed on ampicillin and develops fever, and acute diarrhea with blood and mucus. Laboratory results of Complete blood count (C.B.C) reported leukocytosis and elevated neutrophils count. Which one of the following organisms is the most likely cause of this patient’s diarrhea? A. Staphylococcus aureus. B. Streptococcus pyogenes. C. Clostridium difficile. D. Clostridium perfringens. E. Bacillus cereus.

N Case 5: A 45-year-old tourist returned from a trip to South America and began having cramps and diarrhea. The watery bowel movements came rapidly, one after another, and contained small bits of grayish-white stool. The man was sweaty and nauseated. Upon admission to hospital, 2 liters of fluid were administered intravenously, which was supplemented by oral fluid. The patient was discharged 48 hours after admission. A Gram’s negative non-lactose fermenting non-halophilic rods was isolated by alkaline peptone media. Which of the following microbes produces these symptoms? A. Vibrio parahaemolyticus. D. Helicobacter pylori. B. ETEC. E. Vibrio cholerae. C. Campylobacter jejuni.