Chapter 34: Gastrointestinal Infections and Food Poisoning. Answers Explained

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MULTIPLE CHOICE 1. Why is the travel history of the patient important when evaluating a person with acute diarrhea? a. Travel to different countries puts one at risk for various infections. b. S... ome countries are dirtier than others. c. The United States is clean, and usually bad infections cannot be contracted here. d. All of the above. A Recent travel history is also important, as travelers to underdeveloped areas are at risk for various types of infections. REF: 836 OBJ: Level 2: Interpretation 2. All of these patient history questions will help focus the search for the pathogen except: a. Does the patient have a history of previous gastrointestinal symptoms? b. Did the patient eat any hot food? c. Does the patient have an underlying illness? d. Is the patient taking any medication? B Chronic inflammation, immunosuppression, and medications may themselves be causes for diarrhea. A patient’s diarrhea may not be caused by an infection. REF: 836 OBJ: Level 1: Recall 3. How is diarrhea disease usually contracted? a. By air b. By blood c. By contaminated food or water d. By respiratory droplet C Although there are exceptions, diarrheal pathogens are usually acquired by ingesting a contaminated food or beverage. REF: 836 OBJ: Level 1: Recall 4. How does the small intestine try to prevent infection? a. Caustic secretions b. Acidic secretions c. Anatomic structure d. Peristalsis D The small intestine has a different mechanism to prevent infection—it is constantly in motion (peristalsis). Organisms that rely on adhering to the intestinal wall to cause infection may be hampered by the peristaltic movements. REF: 836 OBJ: Level 2: Interpretation 5. What defense mechanism does the colon have to guard against infection? a. IgA antibody is produced. b. IgE antibody is produced. c. Nonspecific immune defenses are resident here and take care of pathogens. d. The anatomic structure makes it tough for organisms to adhere. A The colon also has defense mechanisms. Antibody is produced locally—primarily IgA—which may have some effect against pathogenic organisms. Also, an enormous number of other bacteria already live in the colon (the host’s normal gut flora). REF: 836 OBJ: Level 1: Recall 6. What is the most common cause of travelers’ diarrhea? a. Giardia lamblia b. Escherichia coli c. Entamoeba histolytica d. Clostridium difficile B Travelers’ diarrhea is most commonly caused by enteropathogenic E. coli. This illness has a short incubation period (usually less than 24 hours) and normally lasts between 1 and 3 days. If a diarrheal illness lasts longer than this or develops in the days or weeks after a traveler returns home, the patient more likely has a different pathogen. REF: 837 OBJ: Level 1: Recall 7. What is the most common cause of death among patients with diarrhea? a. Sepsis b. Septic shock c. Dehydration d. Secondary bacterial infections C The first step in the physical examination of a patient with a diarrheal illness is to determine the patient’s state of hydration, as dehydration is the most common cause of death in patients with diarrhea. REF: 838 OBJ: Level 1: Recall 8. What type of diarrheal illness has no fever and no blood or pus in the stool? a. Diarrhea where the mucosal surface is invaded b. Diarrhea where the full bowel thickness is invaded c. Diarrhea caused by endotoxins d. Diarrhea caused by enterotoxins D The lack of fever and absence of blood or pus in the stool points toward an enterotoxin-mediated illness. The bacteria associated with enterotoxin production do not invade the gut wall, and the toxin does not elicit an inflammatory response, so microscopic examination of the stool does not reveal any red or white blood cells. REF: 839 OBJ: Level 2: Interpretation 9. What type of diarrheal illness has a rapid onset of symptoms after food ingestion (usually less than 12 hours)? a. Diarrhea where the mucosal surface is invaded b. Diarrhea where the full bowel thickness is invaded c. Diarrhea caused by endotoxins d. Diarrhea caused by enterotoxins D The rapid onset of symptoms after food ingestion suggests that the illness in this case is enterotoxin mediated. The preformed toxin is usually present in the contaminated food and is then ingested by the patient, leading to the symptoms. Because toxin may already be present and can act fairly proximally in the bowel, the incubation period is relatively short, usually less than 12 hours. REF: 840 OBJ: Level 2: Interpretation 10. All of the following organisms can cause enterotoxin-mediated diarrhea except: a. Salmonella typhi. b. Clostridium perfringens. c. Vibrio cholerae. d. Staphylococcus aureus. A Enterotoxigenic E. coli accounts for the largest percentage of cases of diarrhea in travelers to underdeveloped areas. Other organisms responsible for enterotoxin-mediated disease are Vibrio cholerae, Staphylococcus aureus, Clostridium perfringens, and Bacillus cereus. REF: 840 OBJ: Level 1: Recall 11. What type of diarrheal illness produces fever, leukocytosis in peripheral blood, and fecal leukocytes? a. Diarrhea in which the mucosal surface is invaded b. Diarrhea in which the full bowel thickness is invaded c. Diarrhea caused by endotoxins d. Diarrhea caused by enterotoxins A As opposed to the enterotoxin-mediated illnesses, organisms that invade the bowel mucosal surface cause an inflammatory response. This is manifested by the presence of fecal leukocytes, and the organisms may also cause fever and leukocytosis in peripheral blood. REF: 840 OBJ: Level 2: Interpretation 12. All the following organisms invade the bowel mucosal surface to produce diarrhea except: a. Salmonella spp. b. Vibrio cholerae. c. Campylobacter spp. d. Shigella spp. B The most common organisms that invade the bowel mucosal surface to produce diarrhea include Salmonella spp., Campylobacter spp., Shigella spp., some Escherichia coli, and Entamoeba histolytica. REF: 840 OBJ: Level 1: Recall 13. What common organism invades the full thickness of the bowel with lymphatic spread? a. Vibrio cholerae b. Campylobacter jejuni c. Salmonella typhi d. Aeromonas spp. C The most common invasive enteric organisms are S. typhi and Yersinia enterocolitica. REF: 840 OBJ: Level 2: Interpretation 14. What diarrheal illness occurs when organisms invade through the bowel wall, cause bacteremia, and also cause a mesenteric lymphadenitis that may be confused with appendicitis? a. Diarrhea in which the mucosal surface is invaded b. Diarrhea in which the full bowel thickness is invaded c. Diarrhea caused by endotoxins d. Diarrhea caused by enterotoxins B Salmonella typhi and Yersinia enterocolitica organisms can invade through the bowel wall, cause bacteremia, and also cause a mesenteric lymphadenitis that may be confused with appendicitis. Diarrhea often is not the presenting symptom, and patients may actually have constipation at the onset of illness. REF: 840 OBJ: Level 2: Interpretation 15. What virus is the leading cause of diarrhea in children younger than age 5? a. Enteric adenoviruses b. Astroviruses c. Rotavirus d. Calicivirus C Rotaviruses are the major cause of diarrhea in children younger than age 5, causing an estimated 130 million episodes of illness worldwide each year. REF: 841 OBJ: Level 1: Recall 16. What virus causes an acute self-limited diarrheal illness that is highly contagious through contaminated food, water, fomites, or person-to-person contact and is associated with vomiting and low-grade fever? a. Astroviruses b. Rotaviruses c. Enteric arenaviruses d. Norovirus D The noroviruses are named after the original strain (Norwalk virus), first isolated in patients from a town with that name in Ohio in 1968. These viruses cause an acute, self-limited diarrheal illness associated with vomiting and low-grade fever. The disease is highly contagious and is transmitted by the fecal-oral route, fecally contaminated food or water, environmental fomites, and by person-to-person contact. REF: 841 OBJ: Level 2: Interpretation 17. Which of the following is an opportunistic virus that can lead to diarrhea in an immunocompromised host? a. Rubella b. Parvo B19 c. Cytomegalovirus d. Filovirus C Cytomegalovirus (CMV) is an opportunistic virus that can lead to diarrhea. Typical symptoms consist of watery diarrhea, pain, and blood in the stool. Fever is often present. REF: 848 OBJ: Level 1: Recall 18. What is the most common cause of bacterial gastroenteritis in the world? a. Salmonella typhi b. Campylobacter jejuni c. Shigella sonnei d. Yersinia enterocolitica B Although various Campylobacter spp. have been isolated as a cause of diarrhea, C. jejuni is the most common bacterial cause of gastroenteritis in the world. REF: 841 OBJ: Level 1: Recall 19. Disease caused by which of the following organisms has fever, abdominal cramping, diarrhea, and stools with gross blood and pus? a. Staphylococcus aureus b. Clostridium difficile c. Campylobacter jejuni d. Bacillus cereus C Infections with this organism usually result in a self-limited disease characterized by fever, abdominal cramping, and diarrhea. The incubation period is normally 2 to 5 days, but in some cases has extended up to 10 days. Diarrhea is often preceded by a period of febrile malaise with myalgias and abdominal pain. Stools may have gross blood and pus present. REF: 842 OBJ: Level 2: Interpretation 20. What is the environmental reservoir of Campylobacter? a. Lakes and rivers b. Fish c. Arthropod vector d. Wild and domestic animals D The environmental reservoir of Campylobacter includes both wild and domestic animals, most frequently birds. This is usually a foodborne infection, often with poultry as the source. REF: 842 OBJ: Level 1: Recall 21. What organism that causes gastroenteritis can be found in aquaculture-farmed fish? a. Salmonella b. Campylobacter c. Vibrio d. Shigella A Nontyphoidal Salmonella spp. can lead to gastroenteritis through ingestion of contaminated meat, poultry, eggs, and dairy products, as well as aquaculture-farmed fish and shellfish. REF: 842 OBJ: Level 2: Interpretation 22. What organ is colonized in a patient that carries Salmonella typhi? a. Colon b. Gallbladder c. Rectum d. Small intestine B The organism can frequently be recovered from both blood and stool cultures. Appropriate antibiotic use results in clinical improvement; however, stool cultures often remain positive, which can serve as a source of infection for other individuals. Some patients can also develop chronic colonization of their gallbladder and biliary tree, leading to persistent shedding of the organism and infections in multiple other people (the classic “Typhoid Mary” case). REF: 842 OBJ: Level 1: Recall 23. What toxin does Shigella spp. produce? a. Typhi b. Enterotoxin c. Shiga d. Campy C The bacteria produce several toxins, one of which is the Shiga toxin, which can have cytotoxic, enterotoxic, and neurotoxic effects. REF: 842 OBJ: Level 1: Recall 24. What diarrheal pathogen can produce a disease that may lead to hemolytic-uremic syndrome (hemolytic anemia, low platelet count, and kidney failure)? a. Enterohemorrhagic Escherichia coli (EHEC) b. Enteroinvasive E. coli (EIEC) c. Enteropathogenic E. coli (EPEC) d. Enterotoxigenic E. coli (ETEC) A EHEC usually starts as a watery diarrhea. However, over the next day or two, abdominal pain increases and stools become bloody. Stool may contain some fecal leukocytes, so there may be some confusion between this infection and EIEC or Shigella. Although the disease is usually self-limited, patients can develop hemolytic-uremic syndrome (HUS), characterized by hemolytic anemia, low platelet count, and kidney failure. REF: 842 OBJ: Level 2: Interpretation 25. What types of stools are characteristic of someone who has cholera? a. Black-blood stools b. Coffee-ground stools c. Black tar stools d. Rice-water stools D Once in the cell, through various enzymatic effects, the toxin results in an increase in the amount of cyclic adenosine monophosphate, which causes the cell to secrete large amounts of water and electrolytes. This increased secretion causes the rice-water stools characteristic of cholera. REF: 843 OBJ: Level 2: Interpretation 26. A man and his family drive to the coast and have an oyster dinner. A couple of days later, the man arrives at the emergency department with a fever, bullous skin lesions, and diarrhea. He is extremely ill and the physician questions whether he is septic. Blood and stool specimens are collected. The microbiologist notices curved gram-negative rods on the stool Gram stain. What is the most probable organism causing this condition? a. Yersinia enterocolitica b. Cryptosporidium jejuni c. Vibrio vulnificus d. Vibrio cholerae C V. vulnificus is the most virulent of all noncholera vibrios, causing an often fulminant illness characterized by sepsis and bullous skin lesions in patients with a recent ingestion of shellfish (i.e., raw oysters). This Vibrio sp. is part of the marine flora, making a common colonizer of a large percentage of oysters harvested in the warmer months. REF: 843 OBJ: Level 3: Synthesis 27. What is the most important cause of iatrogenic diarrhea in adults? a. Yersinia enterocolitica b. Cryptosporidium jejunum c. Vibrio vulnificus d. Clostridium difficile D C. difficile is the most important cause of hospital-acquired diarrhea in adults. This infection demonstrates the importance of normal colonic bacterial flora in preventing disease. REF: 844 OBJ: Level 1: Recall 28. What is the most commonly identified intestinal parasite in the United States? a. Giardia lamblia b. Entamoeba histolytica c. Cryptosporidium parvum d. Microsporidia A The most commonly identified intestinal pathogen in the United States, G. lamblia, is acquired by ingestion of contaminated water and person-to-person spread. REF: 845 OBJ: Level 1: Recall 29. What intestinal parasite is able to leave the intestines and cause metastatic diseases, especially liver abscesses? a. Giardia lamblia b. Entamoeba histolytica c. Cryptosporidium parvum d. Microsporidia B The trophozoites of E. histolytica are able to leave the intestine and can cause metastatic illness, most frequently as a liver abscess. REF: 845 OBJ: Level 1: Recall 30. What condition caused by acute diarrheal disease can significantly contribute to the morbidity and mortality of the disease? a. Metabolic alkalosis b. Metabolic acidosis c. Volume depletion d. Starvation C The most important factor to consider when treating a patient with acute diarrhea is his or her hydration status. Volume depletion and electrolyte derangements are major sources of morbidity and mortality from diarrheal illnesses. Since patients lose electrolytes in diarrheal stools, rehydration cannot occur with water alone. The best hydration solution contains both glucose and sodium. REF: 852 OBJ: Level 2: Interpretation 31. All of the following organisms are commonly implicated in a foodborne outbreak except: a. Staphylococcus aureus. b. Salmonella spp. c. Clostridium botulinum. d. Vibrio cholerae. D Vibrio cholerae causes the disease cholera. The most commonly identified bacterial agents involved in foodborne outbreaks are Salmonella spp., C. jejuni, S. aureus, Clostridium botulinum, and C. perfringens. G. lamblia, Cryptosporidium, and Cyclospora have also been associated with outbreaks, usually linked to contaminated fruits and vegetables. REF: 846 OBJ: Level 1: Recall 32. A microbiologist is reading a Gram stain and observes gram-negative, curved rods with a seagull-wing appearance. What organism could this be? a. Campylobacter or Vibrio b. Shigella or Vibrio c. Campylobacter or Shigella d. All of the above A The bacterial pathogen may be visible on direct microscopic examination of the stool. If gram-negative, curved rods with a sea-gull-wing appearance are present, the patient may have a Campylobacter or Vibrio infection. REF: 849 OBJ: Level 2: Interpretation 33. What organism grows best at 42 C and in a reduced oxygen atmosphere (5% to 10%)? a. Shigella sonnei b. Clostridium difficile c. Campylobacter jejuni d. Escherichia coli C C. jejuni grows best at 42 C and in an atmosphere of reduced oxygen content (5% to 10%), making them microaerophilic organisms. REF: 849 OBJ: Level 1: Recall [Show More]

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