Causative organism of late prosthetic valve endocarditis is :
**Core Concept**
Late prosthetic valve endocarditis (PVE) is a type of infection that occurs months to years after the implantation of a prosthetic heart valve. This condition is often caused by microorganisms that colonize the prosthetic material, leading to a complex interplay between the host immune response, microbial adherence, and biofilm formation.
**Why the Correct Answer is Right**
The correct answer is Staphylococcus epidermidis, a coagulase-negative staphylococcus that is commonly found on human skin. This organism is a leading cause of late PVE due to its ability to adhere to the prosthetic material, form a biofilm, and evade the host immune response. The biofilm matrix produced by S. epidermidis provides a protective environment for the bacteria, allowing them to persist in the face of antibiotic therapy. The pathogenesis of late PVE involves the interaction between S. epidermidis and the prosthetic material, as well as the host immune response, which is often impaired due to the presence of the foreign device.
**Why Each Wrong Option is Incorrect**
* **Option A:** Staphylococcus aureus is a common cause of early PVE, but it is less frequently associated with late PVE.
* **Option B:** Streptococci are also a common cause of endocarditis, but they are more frequently associated with native valve endocarditis rather than PVE.
* **Option D:** Enterococci are a type of gram-positive cocci that can cause endocarditis, but they are not the leading cause of late PVE.
**Clinical Pearl / High-Yield Fact**
To remember the causative organisms of PVE, use the mnemonic "SEPSA": Staphylococcus epidermidis (S), Staphylococcus aureus (E), Pseudomonas (P), Streptococci (S), and Anaerobes (A).
**Correct Answer:** C. Staphylococcus epidermidis.