WBR0382

Author	[[PageAuthor::Yazan Daaboul, M.D. (Reviewed by Yazan Daaboul, M.D.)]]
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Microbiology
Sub Category	SubCategory::Genitourinary
Prompt	[[Prompt::A 38-year-old man presents to the emergency department with complaints of fever and back pain that radiates to the inguinal area. His temperature of 38.5 °C (101.3 °F), heart rate is 98/min, and blood pressure is 122/88 mmHg. Following appropriate work-up, the patient is diagnosed with struvite kidney stone. Urine cultures demonstrate a urea-splitting organism with swarming motility. Which of the following characteristics most likely correspond to the organism responsible for this patient's symptoms?]]
Answer A	AnswerA::Oxidase-positive, catalase-positive, urease-positive
Answer A Explanation	AnswerAExp::''Proteus mirabilis'' is oxidase-negative.
Answer B	AnswerB::Oxidase-negative, catalase-negative, urease-positive
Answer B Explanation	AnswerBExp::''Proteus mirabilis'' is catalase-positive.
Answer C	AnswerC::Oxidase-positive, catalase-negative, urease-negative
Answer C Explanation	AnswerCExp::''Proteus mirabilis'' is oxidase-negative, catalase-positive, and urease-positive.
Answer D	AnswerD::Oxidase-negative, catalase-positive, urease-positive
Answer D Explanation	AnswerDExp::''Proteus mirabilis'' is correctly an oxidase-negative, catalase-positive, urease-positive, gram-negative rod.
Answer E	AnswerE::Oxidase-positive, catalase-positive, urease-negative
Answer E Explanation	AnswerEExp::''Proteus mirabilis'' is oxidase-negative and urease-positive.
Right Answer	RightAnswer::D
Explanation	[[Explanation::Proteus mirabilis is the most common causative agent of struvite stones. It is an oxidase-negative, catalase-positive, urease-positive, gram-negative rod that 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, gram-negative rod with characteristic “swarming” motility in culture. References: First Aid 2014 page 173]]
Approved	Approved::Yes
Keyword	WBRKeyword::Proteus mirabilis, WBRKeyword::Struvite stones, WBRKeyword::Oxidase, WBRKeyword::Catalase, WBRKeyword::Urease, WBRKeyword::Gram negative, WBRKeyword::Rod, WBRKeyword::Swarming motility
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