What is the most common etiologic agent of infections associated with prosthetic devices such as artificial heart valves and CSF shunts?

• A. Corynebacterium urealyticum
• B. Staphylococcus capitis
• C. Staphylococcus epidermidis
• D. Streptococcus mutans

Answer: (C)

Infections on implanted devices are most often caused by organisms that can easily stick to artificial surfaces and form a protective biofilm. Staphylococcus epidermidis is a common skin bacterium that readily adheres to prosthetic materials such as artificial heart valves and CSF shunts and produces a slimy biofilm. This biofilm shields the bacteria from immune defenses and many antibiotics, allowing persistent, low-grade infections around the prosthesis. Because of its frequent presence on implants and its strong biofilm-forming ability, Staphylococcus epidermidis is the most common cause of device-associated infections. Other choices are less typically linked to implanted devices—for example, Streptococcus mutans is associated with dental caries, Corynebacterium urealyticum with urinary infections, and Staphylococcus capitis is less commonly the primary agent for these hardware-related infections.