A 20-year-old woman presents with dysuria and frequency. Urine culture grows coagulase-negative, catalase-positive Gram-positive cocci. It is resistant to novobiocin. Which organism is this, and what is its typical niche?

• A Staphylococcus saprophyticus, genitourinary flora causing cystitis in young women ✓
• B Staphylococcus epidermidis, skin flora causing device infections
• C Enterococcus faecalis, intestinal flora causing urinary tract infection
• D Streptococcus agalactiae, vaginal flora causing ascending infection

Explanation

Novobiocin resistance is the classic laboratory marker of Staphylococcus saprophyticus, which causes acute uncomplicated cystitis in sexually active young women, second only to E. coli in this group. S. epidermidis is novobiocin susceptible and is associated with catheters and prosthetic devices rather than community cystitis. Enterococci are catalase negative, excluding option C.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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