Lippincott Chapter 37: Principles of Antimicrobial Therapy Flashcards
37.1 A 24-year-old pregnant female presents to the urgent
care clinic with fever, frequency, and urgency. She is
diagnosed with a urinary tract infection (UTI). Based
on potential harm to the fetus, which of the following
medications should be avoided in treating her UTI?
A. Nitrofurantoin.
B. Amoxicillin.
C. Cephalexin.
D. Tobramycin
Correct answer = D. Tobramycin (an aminoglycoside) is
considered a pregnancy risk category D drug which means
there is chance for potential harm to the fetus. Nitrofurantoin,
amoxicillin (a penicillin), and cephalexin (a cephalosporin)
are considered category B.
37.2 Which of the following is the primary method of β-lactam
resistance with Streptococcus pneumoniae?
A. Modification of target site.
B. Decreased drug levels due to changes in
permeability.
C. Decreased drug levels due to an efflux pump.
D. Enzymatic inactivation.
Correct answer = A. S. pneumoniae resistance to β-lactam
antibiotics involves alteration in one or more of the major
penicillin-binding proteins
37.3 Which of the following agents is considered a narrow-
spectrum antibiotic?
A. Ceftriaxone.
B. Ciprofloxacin.
C. Isoniazid.
D. Imipenem.
Correct answer = C. Isoniazid is only active against
Mycobacterium tuberculosis, while ceftriaxone, ciprofloxa-
cin, and imipenem are considered broad spectrum due to
their activity against multiple types of bacteria and risk for
developing a superinfection.
37.4 Which of the following antibiotics exhibits concentration-
dependent killing?
A. Clindamycin.
B. Linezolid.
C. Vancomycin.
D. Daptomycin.
Correct answer = D. Clindamycin, linezolid, and vancomycin
exhibit time-dependent killing, while daptomycin works best
in a concentration-dependent fashion.
37.5 Which of the following antibiotics exhibits a long post-
antibiotic effect that permits once-daily dosing?
A. Gentamicin.
B. Penicillin G.
C. Vancomycin.
D. Aztreonam.
Correct answer = A. Aminoglycosides, including gentami-
cin, possess a long post-antibiotic effect, especially when
given as a high dose every 24 hours. Penicillin G, clindamy-
cin, and vancomycin have a relatively short postantibiotic
effect and require frequent dosing to maintain activity.
37.6 A 58-year-old male with a history of hepatitis C,
cirrhosis, and ascites presents with spontaneous
bacterial peritonitis. Which of the following antibiotics
requires close monitoring and dosing adjustment in this
patient given his liver disease?
A. Penicillin G.
B. Tobramycin.
C. Erythromycin.
D. Vancomycin.
Correct answer = C. Erythromycin is metabolized by the liver
and should be used with caution in patients with hepatic
impairment. Penicillin G, tobramycin, and vancomycin are
primarily eliminated by the kidneys.
37.7 Which of the following antibiotics is considered safe to
use in neonates?
A. Chloramphenicol.
B. Sulfamethoxazole/trimethoprim.
C. Tetracycline.
D. Penicillin G.
Correct answer = D. Chloramphenicol and sulfonamides
(sulfamethoxazole) can cause toxic effects in newborns
due to poorly developed renal and hepatic elimination pro-
cesses. Tetracycline can have effects on bone growth and
development and should be avoided in newborns and young
children. Penicillin G is safe and effective in this population.
37.8 All of the following factors influence the penetration
and concentration of an antibacterial agent in the
cerebrospinal fluid except:
A. Lipid solubility of the drug.
B. Minimum inhibitory concentration of the drug.
C. Protein binding of the drug.
D. Molecular weight of the drug.
Correct answer = B. Although the minimum inhibitory con-
centration will impact the effectiveness of the drug against a
given bacteria, it does not affect the ability of a drug to pen-
etrate into the brain. The lipid solubility, protein binding, and
molecular weight all determine the likelihood of a drug to pen-
etrate the blood–brain barrier and concentrate in the brain.
37.9 A 72-year-old male presents with fever, cough, malaise,
and shortness of breath. His chest x-ray shows bilateral
infiltrates consistent with pneumonia. Bronchial wash
cultures reveal Pseudomonas aeruginosa sensitive
to cefepime. Which of the following is the best dosing
scheme for cefepime based on the drug’s time-
dependent bactericidal activity?
A. 1 g every 6 hours given over 30 minutes.
B. 2 g every 12 hours given over 3 hours.
C. 4 g every 24 hours given over 30 minutes.
D. 4 g given as continuous infusion over 24 hours.
Correct answer = D. The clinical efficacy of cefepime is
based on the percentage of time that the drug concentra-
tion remains above the MIC. A continuous infusion would
allow for the greatest amount of time above the MIC com-
pared to intermittent (30 minutes) and prolonged infusions
(3 to 4 hours).
37.10 Which of the following adverse drug reactions
precludes a patient from being rechallenged with that
drug in the future?
A. Itching/rash from penicillin.
B. Stevens-Johnson syndrome from
sulfamethoxazole–trimethoprim.
C. Gastrointestinal (GI) upset from clarithromycin.
D. Clostridium difficile superinfection from
moxifloxacin.
Correct answer = B. Stevens-Johnson syndrome is a
severe idiosyncratic reaction that can be life threatening,
and these patients should never be rechallenged with the
offending agent. Itching/rash is a commonly reported reac-
tion in patients receiving penicillins but is not life threaten-
ing. A patient may be rechallenged if the benefits outweigh
the risk (for example, pregnant patient with syphilis) or the
patient could be exposed through a desensitization proce-
dure. GI upset is a common side effect of clarithromycin but
is not due to an allergic reaction. Moxifloxacin is a broad-
spectrum antibiotic that can inhibit the normal flora of the GI
tract, increasing the risk for the development of superinfec-
tions like C. difficile. This is not an allergic reaction, and the
patient can be rechallenged; however, the patient might be
at risk for developing C. difficile infection again.
