Long-term carriage and shedding is most likely to occur after gastrointestinal infection with which of the following species?
(A) Escherichia coli O157:H7
A 63-year-old man visited his favorite oyster restaurant in a small town on the eastern shore of the Gulf Coast of Texas. He ate two dozen oysters. Two days later, he was admitted to the hospital because of an abrupt onset of chills, fever, and lightheadedness when he stood up. (In the emergency department [ED], his blood pressure was 60/40 mm Hg.) While in the ED, he developed erythematous skin lesions. These rapidly evolved into hemorrhagic bullae, which then formed ulcers. The man drank a six-pack of beer and one half-bottle of whisky each day. A microorganism of major concern for this patient is
(D) Clostridium perfringens
(E) Streptococcus pyogenes (group A streptococci)
A family of four persons ate a meal that included undercooked chicken. Within 3 days, three members developed an illness characterized by fever, headache, myalgia, and malaise. Two of the patients had concomitant diarrhea and abdominal pain. The third person developed diarrhea after the systemic symptoms had cleared. Stool cultures grew Campylobacter jejuni. Which of the following culture conditions was most likely used to isolate C jejuni?
(A) Thiosulfate-citrate-bile-sucrose medium incubated at 37°C in 5% oxygen and 10% CO2
(B) Salmonella-Shigella selective medium incubated at 37°C in ambient air
(C) MacConkey agar and Hektoen enteric agar incubated at 42°C in 5% oxygen and 10% CO2
(D) 5% sheep blood agar incubated at 37°C in ambient air
(E) A medium containing vancomycin, polymyxin B, and trimethoprim incubated at 42°C in 5% oxygen and 10% CO2
Bacteremia associated with a gastrointestinal infection is most likely to occur with which of the following?
(D) Vibrio parahaemolyticus
During the El Niño years in the mid- to late 1990s, the waters of Puget Sound between Washington State and British Columbia warmed considerably. During this time, many people who ate clams and oysters from these waters became ill with a disease characterized by explosive diarrhea and moderately severe abdominal cramps. The diarrhea was usually watery, but in some patients, it was bloody. The diarrhea usually had an onset within 24 hours after eating the shellfish. Stool cultures typically yielded a pathogenic gram-negative bacillus. The microorganism of concern in this setting is
(A) Enterotoxigenic Escherichia coli
(C) Enterohemorrhagic Escherichia coli
(D) Vibrio parahaemolyticus
A patient presents to the emergency department with nonbloody diarrhea for 12 hours. The patient lives in Washington, DC, and has not recently traveled out of the area. Which one of the following is unlikely to be the cause of your patient’s diarrhea?
(A) Salmonella typhimurium
An 18-year-old woman in rural Bangladesh develops profuse (8 L/d) diarrhea. She has no symptoms other than the diarrhea and the manifestations of the fluid and electrolyte loss caused by the diarrhea. The most likely cause of her diarrhea is
(B) Enterotoxigenic Escherichia coli
(C) Salmonella typhimurium
Age and geography are major factors in the prevalence of colonization by Helicobacter pylori. In developing countries, the prevalence of colonization may be greater than 80% in adults. In the United States, the prevalence of colonization with this microorganism in adults older than age 60 years is
A 59-year-old man comes to the emergency department in the afternoon because of acute swelling and pain in his right leg. Earlier that morning, he had been working on a small sport fishing boat in an estuary on the Gulf Coast of Texas. While walking around the boat in shallow water, he scratched his leg, breaking the skin at the site of the current pain and swelling. He was not wearing boots. About 1 hour after the injury, the scratch became red and painful. Swelling developed. Within 3 hours, the leg below the knee had become markedly swollen. The skin was red and tender. There was serous drainage from the wound, which had ulcerated and was now much enlarged. Near the wound, bullae were forming—the largest approximately 2.5 cm in diameter. The most likely cause of this medical emergency is
(A) Staphylococcus aureus
(B) Streptococcus pyogenes
(C) Clostridium perfringens
The Vibrio cholerae factor responsible for diarrhea is a toxin that
(B) Yields increased intracellular levels of cAMP
(D) Blocks EF-1-dependent binding of amino-acyl-tRNA to ribosomes
In September 1854, a severe epidemic of cholera occurred in the Soho/Golden Square area of London. Dr. John Snow, a father of epidemiology, studied the epidemic and helped stop it by which of the following actions?
(A) Banning the sale of apples at the local markets
(B) Removing the handle of the Broad Street water pump
(C) Stopping the sale of shellfish imported from Normandy
(E) Promoted washing vegetables that were consumed raw
A 45-year-old man develops a gastric ulcer that can be visualized on a contrast medium–enhanced radiograph of his stomach. A biopsy specimen is taken from the gastric mucosa at the site of the ulcer. A presumptive diagnosis can be reached most rapidly by inoculating part of the specimen on which of the following?
(A) A medium used to detect urease incubated at 37°C
(B) A medium containing vancomycin, polymyxin B, and trimethoprim incubated at 42°C
(C) MacConkey agar medium incubated at 37°C
(D) Thiosulfate-citrate-bile-sucrose medium incubated at 42°C
(E) Blood agar medium incubated at 37°C