Antimicrobials Practice Questions

Question 1

A 64-year-old woman with a past medical history of poorly managed diabetes presents to the emergency department with nausea and vomiting. Her symptoms started yesterday and have been progressively worsening. She is unable to eat given her symptoms. Her temperature is 102°F (38.9°C), blood pressure is 115/68 mmHg, pulse is 120/min, respirations are 17/min, and oxygen saturation is 98% on room air. Physical exam is notable for left-sided costovertebral angle tenderness, and urinalysis demonstrates bacteriuria and pyuria. The patient is admitted to the hospital and started on IV ceftriaxone. On day 3 of her hospital stay she is afebrile, able to eat and drink, and feels better. Which of the following antibiotic regimens should be started or continued as an outpatient upon discharge?

Accepted Answer

Trimethoprim-sulfamethoxazole

Answer

Amoxicillin

Answer

Nitrofurantoin

Answer

Ciprofloxacin

Answer

Ceftriaxone

Question 2

A 77-year-old woman is brought to the emergency department from her nursing home because she was found down overnight. On presentation she was found to be delirious and was unable to answer questions. Chart review shows that she is allergic to cephalosporins. Her temperature is 102.2°F (39°C), blood pressure is 105/52 mmHg, pulse is 94/min, and respirations are 23/min. Physical exam reveals a productive cough. A metabolic panel is obtained with the following results:

Serum:
Na+: 135 mEq/L
Cl-: 95 mEq/L
K+: 4 mEq/L
HCO3-: 19 mEq/L
BUN: 40 mg/dL
Creatinine: 2.5 mg/dL
Glucose: 150 mg/dL

Based on these findings two different drugs are started empirically. Gram stain on a blood sample is performed showing the presence of gram-positive organisms on all samples. One of the drugs is subsequently stopped. The drug that was most likely stopped has which of the following characteristics?

Accepted Answer

Single-ringed ß-lactam structure

Answer

Resistance conveyed through acetylation

Answer

Associated with red man syndrome

Answer

Causes discolored teeth in children

Answer

Accumulates inside bacteria via O2-dependent uptake

Question 3

A 64-year-old female with type 2 diabetes mellitus comes to the physician because of a 1-week history of painful red swelling on her left thigh. Examination shows a 3- x 4-cm, tender, fluctuant mass. Incision and drainage of the abscess are performed. Culture of the abscess fluid grows gram-positive, coagulase-positive cocci that are resistant to oxacillin. Which of the following best describes the mechanism of resistance of the causal organism to oxacillin?

Accepted Answer

Altered target of the antibiotic

Answer

Degradation of the antibiotic

Answer

Decreased uptake of the antibiotic

Answer

Decreased activation of the antibiotic

Answer

Acetylation of the antibiotic

Question 4

Three days after admission to the hospital following a motor vehicle accident, a 45-year-old woman develops a fever. A central venous catheter was placed on the day of admission for treatment of severe hypotension. Her temperature is 39.2°C (102.5°F). Examination shows erythema surrounding the catheter insertion site at the right internal jugular vein. Blood cultures show gram-positive, catalase-positive cocci that have a high minimum inhibitory concentration when exposed to novobiocin. Which of the following is the most appropriate pharmacotherapy?

Accepted Answer

Vancomycin

Answer

Clarithromycin

Answer

Metronidazole

Answer

Penicillin G

Answer

Polymyxin B

Question 5

A scientist is studying the mechanisms by which bacteria become resistant to antibiotics. She begins by obtaining a culture of vancomycin-resistant Enterococcus faecalis and conducts replicate plating experiments. In these experiments, colonies are inoculated onto a membrane and smeared on 2 separate plates, 1 containing vancomycin and the other with no antibiotics. She finds that all of the bacterial colonies are vancomycin resistant because they grow on both plates. She then maintains the bacteria in liquid culture without vancomycin while she performs her other studies. Fifteen generations of bacteria later, she conducts replicate plating experiments again and finds that 20% of the colonies are now sensitive to vancomycin. Which of the following mechanisms is the most likely explanation for why these colonies have become vancomycin sensitive?

Accepted Answer

Plasmid loss

Answer

Point mutation

Answer

Gain of function mutation

Answer

Viral infection

Answer

Loss of function mutation

Question 6

A 62-year-old man is brought to the emergency department from a senior-care facility after he was found with a decreased level of consciousness and fever. His personal history is relevant for colorectal cancer that was managed with surgical excision of the tumor. Upon admission, he is found to have a blood pressure of 130/80 mm Hg, a pulse of 102/min, a respiratory rate of 20/min, and a body temperature 38.8°C (101.8°F). There is no rash on physical examination; he is found to have neck rigidity, confusion, and photophobia. There are no focal neurological deficits. A head CT is normal without mass or hydrocephalus. A lumbar puncture was performed and cerebrospinal fluid (CSF) is sent to analysis while ceftriaxone and vancomycin are started. Which of the following additional antimicrobials should be added in the management of this patient?

Accepted Answer

Ampicillin

Answer

Trimethoprim-sulfamethoxazole (TMP-SMX)

Answer

Amphotericin

Answer

Meropenem

Answer

Clindamycin

Question 7

A drug that inhibits mRNA synthesis has the well-documented side effect of red-orange body fluids. For which of the following is this drug used as monotherapy?

Accepted Answer

Neisseria meningitidis prophylaxis

Answer

Brucellosis

Answer

Tuberculosis

Answer

Methicillin-resistant staphylococcus aureus infection

Answer

Mycobacterium avium intracellulare infection

Question 8

A 15-year-old boy presents with his father to the urgent care with 5 days of frequent diarrhea, occasionally with streaks of blood mixed in. Stool cultures are pending, but preliminary stool samples demonstrate fecal leukocytes and erythrocytes. His vital signs are as follows: blood pressure is 126/83 mm Hg, heart rate is 97/min, and respiratory rate is 15/min. He is started on outpatient therapy for presumed Shigella infection. Which of the following is the most appropriate therapy?

Accepted Answer

Oral azithromycin

Answer

Oral doxycycline

Answer

Oral vancomycin

Answer

Oral TMP-SMX

Answer

Oral ciprofloxacin

Question 9

An 82-year-old man is brought to the emergency department because of severe pain and joint stiffness in his right knee. The pain started 3 days ago and has worsened despite acetaminophen intake. He has benign prostatic hyperplasia and hypertension. One week ago, he had a urinary tract infection and was treated with nitrofurantoin. He does not smoke or drink alcohol. His current medications include enalapril, hydrochlorothiazide, and tamsulosin. He appears to be in severe pain and has trouble moving his right knee. His temperature is 38.7°C (101.5°F), pulse is 92/min, and blood pressure is 135/90 mm Hg. Physical examination shows a swollen, erythematous, warm right knee; range of motion is limited by pain. Synovial fluid aspiration shows a yellow-green turbid fluid. Gram stain of the synovial aspirate shows numerous leukocytes and multiple gram-negative rods. An x-ray of the right knee shows no abnormalities. Which of the following is the most appropriate pharmacotherapy?

Accepted Answer

IV cefepime

Answer

IV ceftazidime and gentamicin

Answer

IV vancomycin and ceftazidime

Answer

IV vancomycin

Answer

IV nafcillin

Question 10

A 49-year-old man presents to the emergency department with acute onset of pain and redness of the skin of his lower leg for the past 3 days. He has had type 2 diabetes mellitus for the past 12 years, but he is not compliant with his medications. He has smoked 10–15 cigarettes per day for the past 20 years. His temperature is 38°C (100.4°F), pulse is 95/min, and blood pressure is 110/70 mm Hg. On physical examination, the pretibial area is erythematous, edematous, and tender. He is diagnosed with acute cellulitis, and intravenous ceftazidime sodium is started. On the 5th day of antibiotic therapy, the patient complains of severe watery diarrhea, fever, and abdominal tenderness without rigidity. Complete blood count is ordered for the patient and shows 14,000 white blood cells/mm3. Which of the following is the best initial therapy for this patient?

Accepted Answer

Oral vancomycin

Answer

Intravenous vancomycin

Answer

Oral ciprofloxacin

Answer

Fecal microbiota transplantation

Answer

Oral metronidazole

Antimicrobials

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Antiparasitic drugs (antiprotozoals)

Antimalarial medications

Anthelmintics

Antiseptics and disinfectants

Antimicrobial stewardship principles

Empiric antimicrobial selection

Antimicrobial dosing in special populations

Antimicrobial pharmacokinetics/pharmacodynamics

Antimicrobial toxicities

Antimicrobial allergies and cross-reactivity

Combination antimicrobial therapy

Cost-effective antimicrobial strategies

New antimicrobial development

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About Antimicrobials for USMLE

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