Infectious disease · USMLE Step 1 and Step 2

Staph epidermidis & saprophyticus song

Staph epidermidis vs saprophyticus, as a song. Hear the short teaser here. The full song is on YouTube and Spotify.

Staph epidermidis & saprophyticus

Full song on YouTube ↗Spotify ↗

Key points in this song10

Staphylococcus epidermidis is a coagulase-negative Staph and the leading cause of prosthetic valve endocarditis, catheter-associated infections, and infections in immunocompromised or post-surgical patients.
S. epidermidis forms biofilms on prosthetic devices (heart valves, joint prostheses, IV catheters) by producing a polysaccharide slime layer, making it inherently resistant to antibiotics and immune clearance.
S. epidermidis is novobiocin-sensitive, which distinguishes it from S. saprophyticus on laboratory testing.
S. saprophyticus is a coagulase-negative Staph that is novobiocin-resistant — the classic mnemonic: "SAProticus is RESistant" (SAPRES).
S. saprophyticus is the second most common cause of uncomplicated UTI in sexually active young women, after E. coli.
S. saprophyticus UTI classically presents with dysuria, urinary frequency, and a positive urine culture showing gram-positive cocci in clusters with a positive urease test.
Treatment of uncomplicated S. saprophyticus UTI is trimethoprim-sulfamethoxazole or nitrofurantoin; fluoroquinolones are an alternative.
S. epidermidis infections on prosthetic material are treated with vancomycin plus rifampin, because rifampin penetrates biofilms; rifampin is never used alone due to rapid resistance development.
S. epidermidis appearing on a blood culture from a non-immunocompromised patient with no prosthetic device most likely represents a contaminant, not true bacteremia.
Both S. epidermidis and S. saprophyticus are catalase-positive (distinguishing all Staph from Strep) and coagulase-negative (distinguishing them from S. aureus).