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Three months ago, a 53-year-old woman had surgery and chemotherapy for breast cancer. Four weeks ago, she developed a cough occasionally productive of purulent sputum. About 2 weeks ago, she noted a slight but progressive weakness of her left arm and leg. On chest examination, rales were heard over the left upper back when the patient breathed deeply. Neurologic examination confirmed weakness of the left arm and leg. Chest radiography showed a left upper lobe infiltrate. Contrast-enhanced computed tomography showed two lesions in the right hemisphere. Gram stain of a purulent sputum specimen showed branching gram-positive rods that were partially acid fast. Which of the following organisms is the cause of this patient’s current illness?
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(B) Corynebacterium pseudodiphtheriticum
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(C) Aspergillus fumigatus
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(E) Erysipelothrix rhusiopathiae
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Three months ago, a 53-year-old woman had surgery and chemotherapy for breast cancer. Four weeks ago, she developed a cough occasionally productive of purulent sputum. About 2 weeks ago, she noted a slight but progressive weakness of her left arm and leg. On chest examination, rales were heard over the left upper back when the patient breathed deeply. Neurologic examination confirmed weakness of the left arm and leg. Chest radiography showed a left upper lobe infiltrate. Contrast-enhanced computed tomography showed two lesions in the right hemisphere. Gram stain of a purulent sputum specimen showed branching gram-positive rods that were partially acid fast.
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The drug of choice to treat this patient’s infection is
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(B) Trimethoprim–sulfamethoxazole
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(E) A third-generation cephalosporin
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It is particularly difficult to differentiate Erysipelothrix rhusiopathiae from
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(A) Corynebacterium diphtheriae
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(E) Lactobacillus species
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Movement of Listeria monocytogenes inside of host cells is caused by
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(A) Inducing host cell actin polymerization
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(B) The formation of pili (fimbriae) on the listeriae surface
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(D) The motion of listeriae flagella
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An 8-year-old boy, who recently arrived in the United States, develops a severe sore throat. On examination, a grayish exudate (pseudomembrane) is seen over the tonsils and pharynx. The differential diagnosis of severe pharyngitis such as this includes group A streptococcal infection, Epstein-Barr virus (EBV) infection, Neisseria gonorrhoeae pharyngitis, and diphtheria. The cause of the boy’s pharyngitis is most likely:
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(A) A gram-negative bacillus
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(B) A single-stranded positive-sense RNA virus
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(C) A catalase-positive, gram-positive coccus that grows in clusters
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(D) A club-shaped gram-positive bacillus
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(E) A double-stranded RNA virus
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An 8-year-old boy, who recently arrived in the United States, develops a severe sore throat. On examination, a grayish exudate (pseudomembrane) is seen over the tonsils and pharynx. The differential diagnosis of severe pharyngitis such as this includes group A streptococcal infection, Epstein-Barr virus (EBV) infection, Neisseria gonorrhoeae pharyngitis, and diphtheria.
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The primary mechanism in the pathogenesis of the boy’s disease is
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(A) A net increase in intracellular cyclic adenosine monophosphate
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(B) Action of pyrogenic exotoxin (a superantigen)
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(C) Inactivation of acetylcholine esterase
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(D) Action of enterotoxin A
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(E) Inactivation of elongation factor 2
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Corynebacterium jeikeium is
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(C) Often multidrug resistant
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(E) Common but clinically unimportant
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Which of the following aerobic gram-positive bacilli is modified acid-fast positive?
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(A) Nocardia brasiliensis
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(B) Lactobacillus acidophilus
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(C) Erysipelothrix rhusiopathiae
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(D) Listeria monocytogenes
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Skin diphtheria as occurs in children in tropical areas typically
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(A) Does not occur in children who have been immunized with diphtheria toxoid
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(B) Is clinically distinct from skin infections (pyoderma, impetigo) caused by Streptococcus pyogenes and Staphylococcus aureus
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(C) Is also common in northern latitudes
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(D) Results in protective antitoxin levels in most children by the time they are 6–8 years old
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(E) Yields toxin-mediated cardiomyopathy
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A 45-year-old fisherman imbedded a fishhook into his right forefinger. He removed it and did not seek immediate medical therapy. Five days later, he noted fever, severe pain, and nodular-type swelling of the finger. He sought medical therapy. The violaceous nodule was aspirated, and after 48 hours of incubation, colonies of a gram-positive bacillus that caused greenish discoloration of the agar and formed long filaments in the broth culture were noted. The most likely cause of this infection is
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(A) Lactobacillus acidophilus
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(B) Erysipelothrix rhusiopathiae
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(C) Listeria monocytogenes
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(E) Nocardia brasiliensis
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A 45-year-old fisherman imbedded a fishhook into his right forefinger. He removed it and did not seek immediate medical therapy. Five days later, he noted fever, severe pain, and nodular-type swelling of the finger. He sought medical therapy. The violaceous nodule was aspirated, and after 48 hours of incubation, colonies of a gram-positive bacillus that caused greenish discoloration of the agar and formed long filaments in the broth culture were noted.
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A biochemical reaction that is useful in the identification of the causative agent of the infection is
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(B) Acid fastness using modified Kinyoun stain
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Listeria monocytogenes is frequently a foodborne pathogen because
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(A) It can survive at 4°C.
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(B) It survives under conditions of low pH.
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(C) It survives in the presence of high salt concentrations.
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(D) All of the above are correct.
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After recovery on laboratory media, the aerobic Actinomycetes are best identified by
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(A) An automated system used in the laboratory
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(B) Classical biochemicals
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(C) Antigen detection tests such as an ELISA
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(D) Molecular methods such as 16SrRNA gene sequencing
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Which of the following statements regarding Rhodococcus equi is correct?
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(A) It is transmitted person to person.
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(B) It causes tuberculosis in cattle.
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(C) It is a rare cause of pulmonary infection in humans.
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(D) It produces a black pigment on sheep blood agar.
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A hospitalized patient who had an indwelling urinary catheter develops fever, chills, suprapubic pain, and difficulty voiding 48 hours after the catheter is removed. His bladder appears obstructed, and he has white blood cells and bacteria on a urinalysis. Cystoscopy reveals a large bladder stone, and the urine culture grows greater than 10,000 CFU/mL of a short, irregular gram-positive rod. The most likely organism causing this infection is
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(A) Corynebacterium urealyticum
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(B) Nocardia brasiliensis
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(D) Erysipelothrix rhusiopathie
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(E) Lactobacillus acidophilus