USMLE (United States Medical Licensing Examination) Step 1 Practice Exam

Which of the following is associated with Staphylococcus epidermidis infections?

1. Coagulase positive

2. Novobiocin resistant

3. Common in infective endocarditis

4. Common in urinary tract infections

The correct answer is: Common in infective endocarditis

Staphylococcus epidermidis is a coagulase-negative staphylococcus that is part of the normal flora of human skin and mucous membranes. It is known to be a major opportunistic pathogen, especially in individuals with compromised immune systems or those with implanted medical devices such as catheters and prosthetic devices. The infection it causes can often lead to infections associated with devices or biofilms, making it a concerning pathogen in clinical settings. One of the notable associations of Staphylococcus epidermidis infections is its role in infective endocarditis, particularly in patients who have prosthetic heart valves or other cardiac devices. This pathogen can adhere to foreign surfaces in the body and form biofilms, which are protective layers that enable bacteria to resist the host’s immune response and standard treatment. The other options do not accurately reflect the characteristics of Staphylococcus epidermidis. While it is a coagulase-negative organism, it is specifically coagulase-negative rather than positive, and it may exhibit sensitivity to novobiocin, contrary to some other Staphylococcus species. While Staphylococcus species can cause urinary tract infections, Staphylococcus epidermidis is not the primary organism responsible for these infections compared to other pathogens like E. coli.