Blood cultures from a patient with prosthetic valve endocarditis grow a coagulase-negative Staphylococcus. The isolate tests negative with the tube coagulase test and positive with the latex agglutination test for clumping factor. Which species is most likely, and what is its key virulence factor for biofilm formation on prosthetics?

• A Staphylococcus saprophyticus; surface hemagglutinin
• B Staphylococcus lugdunensis; FAME enzyme
• C Staphylococcus epidermidis; polysaccharide intercellular adhesin (PIA) ✓
• D Staphylococcus haemolyticus; fibronectin-binding protein

Explanation

Staphylococcus epidermidis is the most common coagulase-negative Staphylococcus causing prosthetic valve endocarditis and device-related infections. Its key virulence factor is polysaccharide intercellular adhesin (PIA), encoded by the ica operon, which facilitates slime/biofilm formation on implanted materials, protecting bacteria from antibiotics and host immunity. S. lugdunensis is more virulent than other CoNS and can mimic S. aureus clinically. S. saprophyticus causes uncomplicated UTI in young women via hemagglutinin-mediated uroepithelial adherence.

Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.