Page 106 - Review of Medical Microbiology and Immunology ( PDFDrive )

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CHAPTER 11 Antimicrobial Drugs: Resistance
SELF-ASSESSMENT QUESTIONS
organism to penicillin is 1 μg/mL and the MIC to gentamicin
1. The spread of antibiotic resistance from one bacterium to
is 8 μg/mL. However, the MIC to a combination of penicillin
another is a well-recognized and clinically important phe-
and gentamicin is 0.01 μg/mL. Which one of the following
nomenon. Which one of the following mechanisms is most
terms is the most accurate to describe this effect?
likely to be involved with the spread of resistance?
(A) Activation
(A) Acetylation
(B) Antagonism
(B) Conjugation
(C) Reassortment
(C) Programmed rearrangement
(D) Recombination
(D) Protoplast mobility 5. Regarding the mechanisms of resistance to specific drugs,
(E) Synergism
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(E) Translation
2. Regarding the specific mechanisms by which bacteria
which one of the following is most accurate?
become resistant to antimicrobial drugs, which one of the
(A) Certain strains of Enterococcus faecalis produce d-lactate
following is the most accurate?
rather than d-alanine, which causes them to be resistant
(A) Some bacteria contain an enzyme that cleaves the ring of
to vancomycin.
aminoglycosides.
(B) Some bacteria contain clavulanic acid, which binds to
which causes them to be resistant to gentamicin.
penicillin G and inactivates it.
(C) Certain strains of Neisseria gonorrhoeae produce a mutant
(C) Some bacteria contain a mutated gene encoding an
peptidyl transferase, which causes them to be resistant to
altered transpeptidase, which makes it resistant to
tetracycline.
doxycycline.
(D) Certain strains of Streptococcus pyogenes produce a β-lactamase,
(D) Some bacteria contain a mutated gene that encodes an
which causes them to be resistant to erythromycin.
altered RNA polymerase, which makes it resistant to
rifampin. ANSWERS
(E) Some bacteria contain an altered ribosomal protein,
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which makes it resistant to isoniazid.
1. (B)
3. The susceptibility of bacteria to an antibiotic is often deter-
2. (D)
mined by using the minimal inhibitory concentration (MIC)
assay. Regarding the MIC assay, which one of the following is
4. (E)
the most accurate?
5. (A)
(A) MIC is the lowest concentration of the bacteria isolated
from the patient that inhibits the activity of a standard
PRACTICE QUESTIONS: USMLE &
dose of antibiotic.
COURSE EXAMINATIONS
(B) MIC is the lowest concentration of antibiotic that inhibits
the growth of the bacteria isolated from the patient.
(C) MIC is the lowest concentration of antibiotic that kills the
found in the Basic Bacteriology section of Part XIII:
bacteria isolated from the patient.
USMLE (National Board) Practice Questions starting on
(D) MIC is the lowest concentration of antibiotic in the Questions on the topics discussed in this chapter can be
page 709. Also see Part XIV: USMLE (National Board)
patient’s serum that inhibits the activity of a standard dose
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Practice Examination starting on page 751.
of antibiotic.
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