lecture 11 Flashcards
1
Q
- Your patient is a 10-year-old boy who has a high fever and swollen, painful axillary lymph nodes on the left side. His mother says
that he brought home a dead rat a few days ago. You suspect he
may have bubonic plague. Regarding the causative organism,
which one of the following is most accurate?
(A) It has a very low ID50.
(B) It is transmitted from rodents to humans by ticks.
(C) It is endemic primarily in the states along the East Coast of the
United States.
(D) Its main virulence factor is an exotoxin that induces interleukin-2 (IL-2) production by CD4-positive helper T cells.
(E) Infection should be treated with high doses of penicillin G
intravenously.
A
(A) It has a very low ID50.
2
Q
- Your patient is a 20-year-old man who was bitten on the hand
when he tried to break up a fight between two cats yesterday. He
now has a red, hot, tender, swollen lesion at the bite site that has
spread rapidly across his hand. Which one of the following bacteria is the most likely cause of his cellulitis?
(A) Brucella melitensis
(B) Francisella tularensis
(C) Pasteurella multocida
(D) Yersinia pestis
A
(C) Pasteurella multocida
3
Q
- Your patient is a 30-year-old woman who reports that she has
had intermittent fever of 102°F, sweating, and fatigue for the past
one month or so. She has lost her appetite and has lost about
10 pounds in that period. She enjoys eating unpasteurized goat
cheese. On examination, hepatosplenomegaly is detected. A
blood count reveals pancytopenia. Which one of the following
bacteria is the most likely cause of this infection?
(A) Brucella melitensis
(B) Francisella tularensis
(C) Pasteurella multocida
(D) Yersinia pestis
A
(A) Brucella melitensis
4
Q
- Regarding Bartonella henselae, which of the following is most
accurate?
(A) Bartonella henselae is an anaerobic, spore-forming, gram positive rod.
(B) The natural habitat of Bartonella henselae is the cat’s mouth.
(C) Bartonella henselae causes cellulitis in immunocompromised
patients such as AIDS patients.
(D) Diagnosis in the clinical laboratory depends on detecting antibodies in the patient’s serum that will agglutinate cardiolipin.
(E) The drug of choice for Bartonella henselae infections is
metronidazole.
A
(B) The natural habitat of Bartonella henselae is the cat’s mouth.
5
Q
- Your patient is a 25-year-old homeless man who complains of a
cough for the past month. The cough is now productive of several
tablespoons of blood-streaked sputum per day. The sputum is not
foul-smelling. He has lost 10 pounds but says that he doesn’t eat
regularly. On physical exam, temperature is 38°C, and coarse rales
are heard in the apex of the left lung. An acid-fast stain of the
sputum reveals acid-fast rods. Culture of the sputum shows no
growth at 7 days, but buff-colored colonies are visible at 21 days. Of the following organisms, which one is most likely to be the
cause of this infection?
(A) Mycobacterium fortuitum-chelonae
(B) Mycobacterium leprae
(C) Mycobacterium marinum
(D) Mycobacterium tuberculosis - Which one of the following regimens is optimal initial treatment
for the patient in Question 1?
(A) Isoniazid for 9 months
(B) Isoniazid and gentamicin for 2 weeks
(C) Isoniazid and rifampin for 4 months
(D) Isoniazid, rifampin, ethambutol, and pyrazinamide for 2 months
A
(D) Mycobacterium tuberculosis
(D) Isoniazid, rifampin, ethambutol, and pyrazinamide for 2 months
6
Q
- Your patient is a 70-year-old man with progressive weakness in
both legs that began about a week ago. He reports back pain and
fever for the past month. Magnetic resonance imaging (MRI) of
the spine revealed destruction of the seventh thoracic vertebra
and a paravertebral mass. Surgical decompression and debridement were performed. Histologic examination of the mass
revealed caseating granulomas, and Langhans’ giant cells were
observed in the granulomas. Gram stain revealed no organisms,
but an acid-fast stain showed red rods. Culture showed no growth
at 7 days, but growth was seen at 28 days. Of the following, which
one is the most likely cause?
(A) Mycobacterium fortuitum-chelonae
(B) Mycobacterium leprae
(C) Mycobacterium marinum
(D) Mycobacterium tuberculosis
A
(D) Mycobacterium tuberculosis
7
Q
- Your patient is a 30-year-old woman who is infected with HIV
and has a low CD4 count. She now has the findings of pulmonary tuberculosis, but you are concerned that she may be infected
with Mycobacterium avium-intracellulare (MAI). Regarding MAI,
which one of the following is most accurate?
(A) Disseminated disease caused by MAI is typically the result of
decreased antibody production, whereas disseminated disease
caused by M. tuberculosis is typically caused by reduced cellmediated immunity.
(B) Immigrants from Southeast Asia are more likely to be infected
with MAI than with M. tuberculosis.
(C) In the clinical laboratory, MAI forms colonies in 7 days,
whereas M. tuberculosis colonies typically require at least 21 days
of incubation for colonies to appear.
(D) MAI is typically susceptible to a drug regimen of isoniazid and
rifampin, whereas M. tuberculosis is often resistant.
(E) The natural habitat of MAI is the environment, whereas the
natural habitat of M. tuberculosis is humans.
A
(E) The natural habitat of MAI is the environment, whereas the
natural habitat of M. tuberculosis is humans.
8
Q
- Regarding the patient in Question 4, if MAI was shown to be the
cause of her symptoms, which one of the following is the best
choice of antibiotics to prescribe?
(A) Amikacin and doxycycline
(B) Clarithromycin, ethambutol, and rifabutin
(C) Dapsone, rifampin, and clofazimine
(D) Isoniazid and gentamicin
(E) Isoniazid, rifampin, ethambutol, and pyrazinamide
A
(B) Clarithromycin, ethambutol, and rifabutin
9
Q
- Your patient is a 20-year-old man with a single, slowly expanding, nonpainful scaly lesion on his chest for the past 2 months.
The lesion is nonpruritic, and he has lost sensation at the site of
the lesion. He is otherwise well. He is a recent immigrant from
Central America. An acid-fast stain of a scraping of the lesion is
positive. Which one of the following diseases is he most likely to
have?
(A) Cutaneous tuberculosis
(B) Fish tank granuloma
(C) Lepromatous leprosy
(D) Scrofula
(E) Tuberculoid leprosy
A
(E) Tuberculoid leprosy
