USMLE-Rx Step 2 Qmax Challenge #21005

Check out today’s Step 2 CK Qmax Question Challenge.

Know the answer? Post it in the comments below! Don’t forget to check back for an update with the correct answer and explanation (we’ll post it in the comments section below).

USMLE-Rx Step 2 Qmax Challenge #21005A 2-year-old boy is brought to the clinic for evaluation after 2 days of low-grade tactile fever, irritability, and decreased activity. His mother reports that on waking him this morning, his pillow was stained with a small amount of yellow fluid. His heart rate is 92/min, blood pressure is 104/70 mm Hg, respiratory rate is 22/min, and temperature is 38.8°C (101.°F). His external ear canal is normal, and his otoscopic examination is shown in the image.

Which of the following is the most likely bacterial pathogen implicated in this condition?

A. Haemophilus influenzae type B
B. Neisseria meningitidis
C. Pseudomonas aeruginosa
D. Staphylococcus aureus
E. Streptococcus pneumoniae


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This practice question is an actual question from the USMLE-Rx Step 2 CK test bank. Get more Step 2 CK study help atUSMLE-Rx.com.

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8 replies »

  1. The correct answer is E. The patient described is typical for a young child with acute otitis media (AOM). Although patients with AOM can be asymptomatic, many present with myriad symptoms, including ear pulling, ear pain, ear drainage, fever, lethargy, irritability, decreased activity, and decreased appetite, to name a few. The image shown illustrates an otoscopic view of an erythematous, bulging tympanic membrane, which is typical of AOM. Combining the history and the physical examination, this patient is most likely to have a bacterial AOM. The most common pathogen causing about 40% of AOM episodes is Streptococcus pneumoniae.

    A is not correct. Nontypeable Haemophilus influenzae, not the type B form, may cause 25%-30% of episodes of acute otitis media (AOM) and is the second most common cause of this frequent pediatric ailment. H. influenza type B does not usually cause AOM. Although it was once a major cause of meningitis and epiglottitis, it has almost completely disappeared due to widespread inoculation with the Hib vaccine in infancy.

    B is not correct. Neisseria meningitidis is not an important cause of otitis media or otitis externa.

    C is not correct. Pseudmonas aeruginosa is the most common cause of otitis externa but is not a major cause of otitis media and is therefore not the correct answer for this question.

    D is not correct. Studies have implicated Staphylococcus aureus in about 5% of episodes of acute otitis media, making it a relatively rare pathogen for inner ear infections.


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