lecture 13

Question 1

1. Mycoplasma pneumoniae is an important cause of atypical pneumonia. Regarding this organism, which one of the following is the most accurate?
   (A) Amoxicillin is the drug of choice for pneumonia caused by this
   organism.
   (B) Antibody in a patient’s serum will agglutinate human red
   blood cells at 4°C, but not at 37°C.
   (C) Gram stain of the sputum reveals small gram-negative rods.
   (D) It is an obligate intracellular parasite that can only grow within
   human cells in the clinical laboratory.
   (E) People with cystic fibrosis are predisposed to pneumonia
   caused by this organism.

Answer 1

(B) Antibody in a patient’s serum will agglutinate human red
blood cells at 4°C, but not at 37°C.

Question 2

2. Which one of the following is the drug of choice for atypical 
pneumonia caused by M. pneumoniae?
(A) Amoxicillin
(B) Azithromycin
(C) Ceftriaxone
(D) Gentamicin
(E) Vancomycin

Answer 2

(B) Azithromycin

Question 3

1. Your patient is a 65-year-old man with gradually increasing confusion and unsteadiness while walking. A lumbar puncture revealed clear spinal fluid, a normal glucose, and an elevated protein. There were 96 cells/μL, of which 86% were lymphocytes. Gram stain of the cerebrospinal fluid (CSF) was negative. Magnetic resonance imaging (MRI) of the brain was normal. A sample of CSF reacted with beef heart cardiolipin at a titer of 1/1024. Regarding the
   causative organism of his infection, which one of the following is
   most accurate?
   (A) It is transmitted by tick bite.
   (B) Resistance to penicillin G is common, so ceftriaxone should be
   used.
   (C) It has never been grown on bacteriologic media in the clinical
   laboratory.
   (D) It is unlikely to be eradicated because beef cattle are a major
   reservoir for the organism.
   (E) A confirmatory test for this organism utilizes an agglutination
   reaction with the capsular polysaccharide of the organism.

Answer 3

(C) It has never been grown on bacteriologic media in the clinical
laboratory.

Question 4

2. Your patient is a 20-year-old man with an erythematous, macular,
   nonpainful rash on the right arm for the past 4 days. The rash is
   approximately 10 cm in diameter. He also has a fever to 100°F and
   a mild headache. He reports hiking on several weekends recently
   in New York State. You suspect the rash is erythema migrans and that he has Lyme disease. Which one of the following is the best
   approach to confirm your clinical diagnosis?
   (A) Detect IgM antibodies in an ELISA assay
   (B) Determine the titer in a VDRL test
   (C) Gram stain and culture on blood agar incubated aerobically
   (D) Gram stain and culture on blood agar incubated
   (E) Grow on human cells in cell culture and identify with fluorescent antibody
3. Assume the patient in Question 2 does have Lyme disease. Which one of the following antibiotics is the most appropriate to treat his infection?
   (A) Azithromycin or trimethoprim-sulfamethoxazole
   (B) Doxycycline or amoxicillin
   (C) Gentamicin or amikacin
   (D) Metronidazole or clindamycin
   (E) Penicillin G or levofloxacin

Answer 4

(A) Detect IgM antibodies in an ELISA assay

(B) Doxycycline or amoxicillin

Question 5

4. Regarding syphilis, which one of the following is most accurate?
   (A) The characteristic lesion of primary syphilis is a painful vesicle
   on the genitals.
   (B) In secondary syphilis, the number of organisms is low, so the
   chance of transmitting the disease to others is low.
   (C) In secondary syphilis, both the rapid plasma reagin (RPR) and
   the fluorescent treponemal antibody-absorbed (FTA-ABS)
   tests are usually positive.
   (D) The antibody titer in the FTA-ABS test typically declines when
   the patient has been treated adequately.
   (E) In congenital syphilis, no antibody is formed against T. pallidum
   because the fetus is tolerant to the organism.

Answer 5

(C) In secondary syphilis, both the rapid plasma reagin (RPR) and
the fluorescent treponemal antibody-absorbed (FTA-ABS)
tests are usually positive.

Question 6

5. Regarding Borrelia burgdorferi and Lyme disease, which one of
   the following is most accurate?
   (A) Borrelia burgdorferi infects a larger percentage of the rodent
   reservoir in western states, such as California, than in northeastern states, such as New York.
   (B) Pathogenesis of Lyme disease is based on the production of an
   exotoxin that induces interleukin-2 production by T-helper
   cells.
   (C) The vaccine against Lyme disease contains the capsular polysaccharide of all four serotypes as the immunogen.
   (D) Close family members of those infected with Borrelia burgdorferi
   should be given ciprofloxacin.
   (E) Borrelia burgdorferi is transmitted to humans by the bite of
   ticks of the genus Ixodes.

Answer 6

(E) Borrelia burgdorferi is transmitted to humans by the bite of
ticks of the genus Ixodes.

Question 7

6. Benzathine penicillin G is used to treat primary and secondary
   syphilis rather than procaine penicillin G. Which one of the following is the best reason for this choice?
   (A) Patients allergic to procaine penicillin G are not allergic to
   benzathine penicillin G.
   (B) Benzathine penicillin G has a higher minimal inhibitory concentration than procaine penicillin G.
   (C) Benzathine penicillin G penetrates the central nervous system
   to a greater degree than procaine penicillin G.
   (D) Benzathine penicillin G is a depot preparation that provides a
   long-lasting, high level of drug that kills the slow-growing
   Treponema pallidum.

Answer 7

(D) Benzathine penicillin G is a depot preparation that provides a
long-lasting, high level of drug that kills the slow-growing
Treponema pallidum.