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A 68-year-old woman was seen in the clinic because she had felt feverish and had been experiencing increasing pain and swelling in her left knee during the past 3 weeks. Four years earlier, a prosthetic joint had been placed in her left knee. On examination, the knee was swollen, and fluid could be detected. An aspirate of the fluid was obtained. There were 15,000 polymorphonuclear cells/mL in the fluid. No organisms were seen on Gram stain. A routine culture was done. On the fourth day of incubation, colorless colonies smaller than 1 mm in diameter were seen on the blood and chocolate agar plates. The organism was a tiny gram-negative coccobacillus that was catalase positive and oxidase positive. A urea slant was inoculated and was positive for urease activity after overnight incubation. The patient was probably infected with which of the following microorganisms?
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(A) Haemophilus influenzae
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(C) Francisella tularensis
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(E) Staphylococcus aureus
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A 68-year-old woman was seen in the clinic because she had felt feverish and had been experiencing increasing pain and swelling in her left knee during the past 3 weeks. Four years earlier, a prosthetic joint had been placed in her left knee. On examination, the knee was swollen, and fluid could be detected. An aspirate of the fluid was obtained. There were 15,000 polymorphonuclear cells/mL in the fluid. No organisms were seen on Gram stain. A routine culture was done. On the fourth day of incubation, colorless colonies smaller than 1 mm in diameter were seen on the blood and chocolate agar plates. The organism was a tiny gram-negative coccobacillus that was catalase positive and oxidase positive. A urea slant was inoculated and was positive for urease activity after overnight incubation.
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After the culture turned positive, additional history was obtained. Approximately 4 weeks before the onset of her knee pain, the patient had visited relatives in Israel and traveled to other countries in the Mediterranean area. She had a particular fondness for one food product that was the probable vehicle for her infection. The product most likely was
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(B) Unpasteurized goat’s cheese
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A 55-year-old game warden in Vermont found a dead muskrat on the bank of a stream. He picked up the animal, thinking it might have been illegally trapped or shot; it was not, and the game warden buried it. Four days later, he developed a 1.5-cm painful ulcer on the index finger of his right hand, a 1-cm ulcer on his right forehead, and pain in his right axilla. Physical examination also revealed right axillary lymphadenopathy. This patient is most likely infected with
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(B) Rickettsia rickettsii
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(E) Francisella tularensis
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An 18-month-old boy has been playing with a child who develops Haemophilus influenzae meningitis. The boy’s parents consult his pediatrician, who says she is comfortable that the child will be fine because he has been fully immunized with the polyribitol ribose phosphate (PRP)–protein conjugate vaccine. For what reason is it necessary to immunize infants of 2 months to 2 years of age with polysaccharide–protein conjugate vaccines?
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(A) The conjugate protein is diphtheria toxoid, and the goal is for the infant to develop simultaneous immunity to diphtheria.
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(B) Infants 2 months to 2 years of age do not immunologically respond to polysaccharide vaccines that are not conjugated to a protein.
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(C) The conjugate vaccine is designed for older children and adults as well as infants.
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(D) Maternal (transplacental) antibodies against Haemophilus influenzae are gone from the infant’s circulation by 2 months of age.
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An 11-year-old boy from Peru was referred to the Brain Tumor Institute. Three months earlier he had developed headaches and then slowly progressive right-sided weakness. A CT scan showed a mass lesion in the left hemisphere. He was thought to have a brain tumor. A lumbar puncture was not done because of concern about increased intracranial pressure and brain herniation through the tentorium cerebelli. During surgery, a mass lesion in the left hemisphere was found. Frozen sections of the tissue were done while the patient was in the operating room. Microscopy of the sections showed a granulomatous inflammatory reaction. No tumor was seen. Tissue was submitted for culture for Mycobacterium tuberculosis. Middlebrook 7H9 broth medium was used. Six days after the culture was set up, the automated machine detected that the culture result was positive. Results of an acid-fast stain and a Gram stain were both negative. Subcultures were done. Two days later, very small colonies were seen on the sheep blood agar plate. The organism was a tiny gram-negative coccobacillus that was catalase positive and oxidase positive. It showed urease activity after 2 hours of incubation on urea-containing medium. This child had infection with
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(B) Mycobacterium tuberculosis
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(C) Francisella tularensis
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(D) Haemophilus influenzae
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(E) Moraxella catarrhalis
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A 3-year-old child develops Haemophilus influenzae meningitis. Therapy is begun with cefotaxime. Why is this third-generation cephalosporin used rather than ampicillin?
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(A) About 80% of Haemophilus influenzae organisms have modified penicillin-binding proteins that confer resistance to ampicillin.
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(B) The drug of choice, trimethoprim–sulfamethoxazole, cannot be used because the child is allergic to sulfonamides.
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(C) It is easier to administer intravenous cefotaxime than intravenous ampicillin.
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(D) There is concern that the child will rapidly develop a penicillin (ampicillin) allergy.
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(E) About 20% of Haemophilus influenzae organisms have a plasmid that encodes for β-lactamase.
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A 55-year-old man with severe dental caries presented with 1 month of fever, malaise, and back pain and now presents with moderately severe shortness of breath. The examination reveals a febrile man who appears pale and dyspneic. Other physical findings include conjunctival petechiae, a grade III/VI systolic murmur, and an enlarged spleen. Blood cultures grow a pleomorphic gram-negative rod that is not hemolytic and that when tested is X and V factor negative. The most likely causative pathogen is
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(A) Haemophilus influenzae
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(C) Aggregatibacter aphrophilus
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(D) Actinobacillus hominis
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(E) Haemophilus parainfluenzae
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All of the following statements regarding acellular pertussis vaccines are correct except
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(A) All formulations of the vaccine contain at least two antigens.
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(B) The acellular vaccine has replaced the whole cell vaccine in the childhood vaccine series.
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(C) All children should receive five doses of the vaccine before school entry.
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(D) The vaccine is approved only for young children and adolescents.
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(E) The vaccine is safer than and as immunogenic as whole-cell vaccines.
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Which of the following subspecies of Francisella tularensis is the most virulent for humans?
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All of the following statements regarding the etiologic agent of chancroid are correct except
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(A) The organism is a small gram-negative rod.
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(B) The organism requires X factor but not V factor.
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(C) The organism grows well on standard chocolate agar.
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(D) On Gram stain of lesions, the organism occurs in strands.
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(E) The organism is susceptible to erythromycin.
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A 3-month-old infant is brought to the pediatric emergency department in severe respiratory distress. The child appears dehydrated, and there is a prominent peripheral lymphocytosis. The chest radiograph reveals perihilar infiltrates. The child’s grandmother, who watches the infant now that the mother has returned to work, has had a dry hacking cough for about 2 weeks. The most likely causative agent is
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(A) Haemophilus influenzae type b
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(C) Streptococcus agalactiae
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(E) Bordetella bronchiseptica
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A 3-month-old infant is brought to the pediatric emergency department in severe respiratory distress. The child appears dehydrated, and there is a prominent peripheral lymphocytosis. The chest radiograph reveals perihilar infiltrates. The child’s grandmother, who watches the infant now that the mother has returned to work, has had a dry hacking cough for about 2 weeks.
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The factor responsible for the profound lymphocytosis is
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(B) A polysaccharide capsule
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(C) An A/B structured toxin
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All of the following cause zoonotic infections except
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(A) Francisella tularensis
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(E) Leptospira interrogans
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Which of the following is not a recognized virulence factor of Bordetella pertussis?
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(B) Filamentous hemagglutinin
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Which of the following pathogens discussed in this chapter is on the select agent list?
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(A) Haemophilus influenzae
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(B) Aggregatibacter aphrophilus
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(D) Francisella tularensis
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