A 20-year-old college student goes to the student health center because of dysuria, frequency, and urgency on urination for 24 hours. She has recently become sexually active. On urinalysis, many polymorphonuclear cells are seen. The most likely organism responsible for these symptoms and signs is
(A) Staphylococcus aureus
(B) Streptococcus agalactiae
(C) Gardnerella vaginalis
(D) Lactobacillus species
A 27-year-old woman is admitted to the hospital because of fever, with increasing anorexia, headache, weakness, and altered mental status of 2 days’ duration. She works for an airline as a cabin attendant, flying between the Indian subcontinent and other places in Southeast Asia and the West Coast of the United States. Ten days before admission, she had a diarrheal illness that lasted for about 36 hours. She has been constipated for the past 3 days. Her temperature is 39°C, heart rate is 68 beats/min, blood pressure is 120/80 mm Hg, and respirations are 18 breaths/min. She knows who she is and where she is but does not know the date. She is picking at the bedclothes. Rose spots are seen on her trunk. The remainder of the physical examination is normal. Blood cultures are done, and an intravenous line is placed. The most likely cause of her illness is
(A) Enterotoxigenic Escherichia coli (ETEC)
(C) Salmonella enterica subspecies enterica serotype Typhimurium (Salmonella Typhimurium)
(D) Salmonella enterica subspecies enterica serotype Typhi (Salmonella Typhi)
(E) Enteroinvasive Escherichia coli (EIEC)
A 27-year-old woman is admitted to the hospital because of fever, with increasing anorexia, headache, weakness, and altered mental status of 2 days’ duration. She works for an airline as a cabin attendant, flying between the Indian subcontinent and other places in Southeast Asia and the West Coast of the United States. Ten days before admission, she had a diarrheal illness that lasted for about 36 hours. She has been constipated for the past 3 days. Her temperature is 39°C, heart rate is 68 beats/min, blood pressure is 120/80 mm Hg, and respirations are 18 breaths/min. She knows who she is and where she is but does not know the date. She is picking at the bedclothes. Rose spots are seen on her trunk. The remainder of the physical examination is normal. Blood cultures are done, and an intravenous line is placed.
Blood cultures from the patient grow a non–lactose-fermenting gram-negative bacillus. Which of the following is likely to be a constituent of this organism?
(A) O antigen 157, H antigen 7 (O157:H7)
(B) Vi antigen (capsule; virulence antigen)
A 37-year-old woman with a history of urinary tract infections comes to the emergency department with burning on urination along with frequency and urgency. She says her urine smells like ammonia. The cause of her urinary tract infection is likely to be
(A) Enterobacter aerogenes
An 18-year-old student has abdominal cramps and diarrhea. A selective agar plate is inoculated and grows suspicious gram-negative rods. Triple sugar iron agar is used to identify the isolates as salmonellae or shigellae. A result suggesting one of these two pathogens would be
(B) Motility in the medium
(C) Inability to ferment lactose and sucrose
(D) Fermentation of glucose
(E) Production of gas in the medium
An uncommon serotype of Salmonella enterica subspecies enterica was found by laboratories in the health departments of adjacent states. The isolates were all from a small geographic area on either side of the border between the states, suggesting a common source for the isolates. (All of the isolates were from otherwise healthy young adults who smoked marijuana; the same Salmonella was isolated from a specimen of the marijuana.) By what method did the public health laboratories determine that these isolates were the same?
(A) Capsular (K antigen) typing
(B) O antigen and H antigen typing
(D) Sugar fermentation pattern determination
(E) Decarboxylase reaction pattern determination
A 43-year-old man with diabetes has a 4-cm nonhealing foot ulcer. Culture of the ulcer yields Staphylococcus aureus, Bacteroides fragilis, and a gram-negative bacillus that swarms across the blood agar plate covering the entire surface of the agar after 36 hours. The gram-negative bacillus is a member of the genus
A 4-year-old boy from Kansas City who recently started attending preschool and after-school daycare is brought to his pediatrician for a diarrheal illness characterized by fever to 38.2°C, severe lower abdominal pain, and initially watery diarrhea. His mother became concerned because the stools are now blood tinged 24 hours into the illness, and the child appears quite ill. The mother reports that two other children who attend the same after-school daycare have recently had diarrheal disease, one of whom likewise had bloody stools. Which of the following is the most likely pathogen causing the illness in these children?
(A) An enterotoxigenic strain of Escherichia coli
(B) Salmonella enterica subspecies enterica serotype Typhi (Salmonella Typhi)
A 5-year-old girl attended a birthday party at a local fast food restaurant. About 48 hours later, she developed cramping abdominal pain and a low-grade fever and had five episodes of loose, bloody stools. She is taken to a local emergency department the next evening because the diarrhea has continued, and she now appears pale and lethargic. On presentation, she has a temperature of 38°C, and she is hypotensive and tachycardic. The abdominal examination reveals tenderness in the lower quadrants. Laboratory work is remarkable for a serum creatinine of 2.0 mg/dL, a serum hemoglobin of 8.0 mg/dL, thrombocytopenia, and evidence of hemolysis. What is the most likely pathogen causing this child’s illness?
(A) Escherichia coli O157:H7
(B) Salmonella enterica subspecies enterica serotype Typhimurium
(C) Enteropathogenic Escherichia coli
(E) Plesiomonas shigelloides
A 55-year-old homeless man with alcoholism presents with severe multilobar pneumonia. He requires intubation and mechanical ventilation. A Gram stain of his sputum reveals numerous polymorphonuclear leukocytes and gram-negative rods that appear to have a capsule. The organism is a lactose fermenter on MacConkey agar and is very mucoid. It is nonmotile and lysine decarboxylase positive. What is the most likely organism causing this man’s illness?
(B) Enterobacter aerogenes
(D) Klebsiella pneumoniae
Which of the following statements regarding O antigens is correct?
(A) All Enterobacteriaceae possess identical O antigens.
(B) They are found in the polysaccharide capsules of enteric bacteria.
(C) They are covalently linked to a polysaccharide core.
(D) They do not stimulate an immune response in the host.
(E) They are not important in the pathogenesis of infection caused by enteric bacteria.
Which of the following test methods is the least sensitive procedure for diagnosis of colitis caused by Shiga toxin–producing Escherichia coli?
(A) Culture on sorbitol MacConkey agar
(B) Toxin testing using an enzyme immunoassay
(C) Cell culture cytotoxin assay using Vero cells
(D) Polymerase chain reaction for detection of the genes that encode Shiga toxin
An HIV-positive man recently traveled to the Caribbean for a 2-week vacation. He developed acute watery diarrhea and abdominal pain without fever during the second week of his vacation. Three weeks later, he is seen in clinic for persistent symptoms, and he is concerned because he is beginning to lose weight. Given this history, you suspect:
(A) Enteroinvasive Escherichia coli
(C) Enteropathogenic Escherichia coli
(E) Enteroaggregative Escherichia coli
Heat-labile toxin of ETEC acts by which of the following mechanisms?
(A) Attachment and effacement
(B) Activation of adenylyl cyclase
(C) Aggregative adherence
(D) Ribosomal dysfunction
A young woman presents with recurrent urinary tract infections caused by the same Proteus mirabilis strain. What is the major concern?
(A) She does not take her medication.
(B) She is pregnant because pregnant patients are more susceptible to UTIs.
(C) She has a bladder or kidney stone.
(D) Her partner is infected.
(E) She has occult diabetes and should have a glucose tolerance test.