This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Microbiology
True statement regarding non-coagulase staphylococci is - 
Select and explain. 
A. They are non-pathogenic, B. They commonly infect indwelling prosthesis, C. They may cause scarlet fever, D. They are seperated by gram staining
B: They commonly infect indwelling prosthesis
Answer: B: They commonly infect indwelling prosthesis 
Explanation: Staph epidermidis 

Most common coagulase negative staph. causing human infections.
It is present on the normal human skin (where it is the most abundant bacterial species) as well as in the oropharynx and vagina.
It is a common cause of stitch abscesses.
It has a predilection for growth on the implanted foreign bodies such as artificial heart valves, shunts, intravascular catheters and prosthetic appliances leading to bacteremia.
S. epidermidis is uniquely adopted to colonize these devices by its capacity to elaborate the extracellular poly­saccharide (slime) that facilitates the formation of a protective biofilm (slime layer) on the device surface. This biofilm acts as a barrier protecting bacteria from host defense mechanisms as well as from antibiotics.
The surface - associated staphylococcal enzyme autolysin (Atle) may play a role in attachment to prosthetic surfaces, which are often coated with host serum or tissue constituents such as fibrinogen or fibronectin.
It can cause cystitis and endocarditis.