MedSmarter Question Break Down of the Week - Micro - 07/07/2021

QBDOTW: A 50-year-old Obese Female Patient w/ Diabetes Mellitus

Welcome to MedSmarter’s USMLE Style Question Break Down of the Week.  For those preparing for the USMLE Step 1, this week we break down a high-yield Microbiology question.  As always you want to begin with reading the last sentence of the vignette first to get an understanding of what the question is asking for.

Question Break Down of the Week:

A 50-year-old obese female with poorly controlled non-insulin-dependent diabetes mellitus presents with fever to 39.4° C (102.9° F), jaundice, hypotension, and acute onset of right upper quadrant pain. Abdominal imaging shows multiple gallstones and cholecystitis. Urgent cholecystectomy is performed, and subsequent gall bladder fluid and blood cultures grow aerobic, non-lactose-fermenting, oxidase-positive, gram-negative rods. Blood tests show:

Hematocrit: 25%
WBC count: 15,300/mm3
Platelet count: 80,000/mm3
International Normalized Ratio: 3.2
D-dimer: 8200 ng/mL
Fibrinogen levels: low

Microscopic inspection of peripheral blood smear shows schistocytes and multiple helmet cells. Clinically, there is no evidence of active bleeding. What is the most appropriate treatment for this patients’ coagulopathy?

A)  Fresh frozen plasma
B)  Vancomycin
C)  Amoxicillin
D)  Aztreonam
E)  Vitamin K

The correct answer is D. This patient has Charcot’s triad (fever, jaundice, right upper quadrant pain) paired with leukocytosis, along with low blood pressure, giving us a clear clinical picture of cholecystitis. On top of that, he has Pseudomonas aeruginosa (aerobic, non-lactose-fermenting, oxidase-positive, gram-negative rods) sepsis and disseminated intravascular coagulation (DIC). Gram-negative rod sepsis is the obvious cause of this patient’s DIC, and antipseudomonal coverage with aztreonam is most appropriate. Aztreonam is a β-lactamase-resistant monobactam that interferes with cell wall biosynthesis by binding to penicillin-binding protein 3. Aztreonam is a potent antipseudomonal agent indicated for pseudomonal sepsis. Aztreonam has low bioavailability when given orally, so it is either IV or nebulized.

Did you think the answer was different?

Did you think that the correct answer choice was other than D?  You can view this video for a deeper discussion of why A, B, C, and E were not the correct answer choices.

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