WBR0945

Author	[[PageAuthor::William J Gibson (Reviewed by Yazan Daaboul, M.D.)]]
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Microbiology
Sub Category	SubCategory::Genitourinary
Prompt	[[Prompt::A sexually active 22-year-old woman presents to her primary care physician with complaints of burning sensation on urination for the past 2 days. Urine culture demonstrates colonies of catalase-positive, coagulase-negative, gram-positive cocci with novobiocin resistance. Which of the following pathogen's is most likely responsible for this patient's condition?]]
Answer A	AnswerA::''Escheria coli''
Answer A Explanation	AnswerAExp::While ''E. coli'' is the leading cause of urinary tract infections among sexually active women, ''E.coli'' is a gram-negative rod.
Answer B	AnswerB::''Staphylococcus aureus''
Answer B Explanation	AnswerBExp::While ''S. aureus'' is a catalase-positive, gram-positive coccus, it is coagulase-positive.
Answer C	AnswerC::''Staphylococcus epidermidis''
Answer C Explanation	[[AnswerCExp::S. epidermidis is a catalase-positive, coagulase-negative, gram-positive coccus with novobiocin sensitivity. S. epidermidis is a component of the normal skin flora but can become pathogenic typically by infecting prosthetic devices. It is a common cause of endocarditis among patients with artificial valves.]]
Answer D	AnswerD::''Staphylococcus saprophyticus''
Answer D Explanation	AnswerDExp::''S. Saprophyticus'' is a catalase-positive, coagulase-negative, gram-positive coccus with novobiocin resistance. It is the second most common cause of urinary tract infections among sexually active women, following ''E. coli''.
Answer E	AnswerE::''Streptococcus agalactiae''
Answer E Explanation	AnswerEExp::''S agalactiae'' is a catalase-negative, beta-hemolytic, gram-positive coccus with bacitracin resistance. It is alternatively referred to as Group B streptococci and is a common cause of neonatal meningitis.
Right Answer	RightAnswer::D
Explanation	[[Explanation::The patient in this vignette has a urinary tract infection caused by Staphylococcus saprophyticus. S. saprophyticus is a catalase-positive, coagulase-negative, gram-positive coccus with novobiocin resistance. It is the second most common cause of urinary tract infections among sexually active women (10-20%) following E. coli. Educational Objective: S. Saprophyticus is a catalase-positive, coagulase-negative, gram-positive coccus with novobiocin resistance. It is the second most common cause of urinary tract infections among sexually active women. References: Hovelius, Birgitta, and Per-Anders Mardh. Staphylococcus saprophyticus as a common cause of urinary tract infections. Review of Infectious Diseases. 1984; 6(3):328-337. First Aid 2015 page 174.]]
Approved	Approved::Yes
Keyword	WBRKeyword::Bacteria, WBRKeyword::Staphylococcus saprophyticus, WBRKeyword::Gram positive, WBRKeyword::Gram positive bacteria, WBRKeyword::UTI, WBRKeyword::Urinary tract infection, WBRKeyword::Laboratory classification, WBRKeyword::Catalase, WBRKeyword::Novobiocin, WBRKeyword::Coagulase
Linked Question	Linked::
Order in Linked Questions	LinkedOrder::