WBR0382

Author	[[PageAuthor::Rim Halaby, M.D. [1] (Reviewed by Alison Leibowitz)]]
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Microbiology
Sub Category	SubCategory::Genitourinary
Prompt	[[Prompt::A 38-year-old male presents to the ER with complaints of fever and back pain, radiating to the inguinal area. Vital signs reveal a temperature of 38.5 °C, heart rate of 98 beats per minute, and blood pressure measuring 122/88 mmHg. Following appropriate work-up, you diagnose him with struvite stone and preform a stone and urine culture. The cultures reveal a urea-splitting organism with swarming motility. Which of the following characteristics most likely corresponds to this organism?]]
Answer A	AnswerA::Oxidase-positive, catalase-positive, urease-positive
Answer A Explanation	AnswerAExp::''Proteus mirabilis'' is not oxidase-positive.
Answer B	AnswerB::Oxidase-negative, catalase-negative, urease-positive
Answer B Explanation	AnswerBExp::''Proteus mirabilis'' is not catalase-positive.
Answer C	AnswerC::Oxidase-positive, catalase-negative, urease-negative
Answer C Explanation	AnswerCExp::''Proteus mirabilis'' is not oxidase-positive, catalase-negative, nor urease-negative.
Answer D	AnswerD::Oxidase-negative, catalase-positive, urease-positive
Answer D Explanation	AnswerDExp::''Proteus mirabilis'' is correctly an oxidase-negative, catalase-positive, urease-positive organism.
Answer E	AnswerE::Oxidase-positive, catalase-positive, urease-negative
Answer E Explanation	AnswerEExp::''Proteus mirabilis'' is not oxidase positive nor urease-negative.
Right Answer	RightAnswer::D
Explanation	[[Explanation::Proteus mirabilis, a causative agent of struvite stones, is an oxidase-negative, catalase-positive, urease-positive organism, which has a characteristic “swarming” motility in cultures. Proteus mirabilis is a known pathogen of the urogenital tract. Other examples of urea-splitting organisms are Pseudomonas, Klebsiella, Staphylococcus, and Mycoplasma. Educational Objective: Proteus mirabilis is a common causative agent of struvite stones. It is an oxidase-negative, catalase-positive, urease-positive organism with characteristic “swarming” motility. References: First Aid 2014 page 173]]
Approved	Approved::Yes
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