Diarrheal diseases are one of the leading causes of death worldwide, with poverty, lack of sanitation, and lack of good nutrition contributing to the vicious cycle of disease, malnutrition, and death. World wide, rotaviruses, E. coli, and Campylobacter jejuni are the leading causes of these illnesses. Amoeba and parasitic worms are also significant problems in many countries. In the US, viruses, Campylobacter, Shigella, and Salmonella are major causes. Pathogenic E. coli is difficult to test for due to the presence of an abundant non-pathogenic intestinal flora containing E. coli, although tests are available for specific strains such as E. coli 0157:H7. C. difficile is a nosocomial cause of a serious diarrhea. While not an infection, food intoxication (food poisoning) is a common cause of illness in the US and other countries. The term food poisoning should be reserved for true food intoxications, where bacteria need not be ingested, or if ingested, need not colonize; however, infections acquired from food are often (incorrectly) called food poisoning. The diarrheal infections are of two main types, 1) secretory or watery, and 2) inflammatory. The latter is sometimes referred to as dysentery. The pathogenesis of the two types is fundamentally different and contributes to their different symptomology. In secretory or watery diarrhea a bacterial toxin or virus alters the fluid balance in the intestines. In inflammatory diarrhea there is invasion of the intestinal wall with subsequent inflammation and release white blood cells and sometimes red blood cells into the lumen of the intestine. Enteric fever, such as typhoid fever, is a systemic disease that begins in the GI tract, but may not have any GI symptoms. In enteric fevers, the organisms invade through the intestine and become systemic. Chapter 8, pp 241 to 262, of Infectious Diseases in 30 Days by F.S. Southwick (McGraw-Hill, 2003) discusses these diseases from the point of view of a physician in the US (note that Salmonella nomenclature has been changed since this was written, see the Bugs index). After reading this, or the introduction to GI diseases in any Microbiology text book, you should be able to answer the following questions.
Question 1 - Single Best Answer
What is the primary non-specific host defense protecting the GI tract?
non-specific phagocytes killer T-cells complement stomach acid constant mucosal surface washing
Question 2 - Single Best Answer
What easy test detects Salmonella and/or Shigella in a stool sample?
Gram stain no growth on blood agar beta hemolysis on blood agar light color of colonies on EMB or MacConkeys agar plates acid-fast stain
Question 3 - Single Best Answer
Which of the following can reduce the inoculum size necessary to cause illness for Salmonella?
antacids antibiotics AIDS two of the above all of the above
Question 4 - Single Best Answer
Which of the following are most likely to be contaminated with Salmonella?
eggs and chicken beef milk apples raw oysters
Question 5 - Single Best Answer
What is the major difference in the epidemiology of Salmonella and Shigella
only elderly people get Shigella only individuals with AIDS get Salmonella Shigella is only transmitted from humans, not animals Shigella can be transmitted by water but Salmonella cannot only children get Shigella
Question 6 - Single Best Answer
Which of the following are true of Campylobacter?
Gram negative curved rod grows best at 42 degrees C transmitted from a variety of farm animals, raw milk, and chickens all of the above
Question 7 - Single Best Answer
What bacterium is associated almost exclusively with antibiotic-associated diarrhea?
Staphylococcus aureus Candida albicans Clostridium perfringins Clostridium difficile Salmonella typhi
Question 8 - Single Best Answer
Where do the bacteria come from that cause pseudomembranous (antibiotic associated) colitis?
the patientŐs GI tract the doctors the nurses water keeping flowers fresh improperly manufactured antibiotics