A 56-year-old woman comes to the emergency department because of worsening pain and swelling in her right knee for 3 days. She underwent a total knee arthroplasty of her right knee joint 5 months ago. The procedure and immediate aftermath were uneventful. She has hypertension and osteoarthritis. Current medications include glucosamine, amlodipine, and meloxicam. Her temperature is 37.9°C (100.2°F), pulse is 95/min, and blood pressure is 115/70 mm Hg. Examination shows a tender, swollen right knee joint; range of motion is limited by pain. The remainder of the examination shows no abnormalities. Blood cultures repeatedly grow gram-positive cocci in clusters, which are identified as Staphylococcus epidermidis. This pathogen most likely demonstrates which of the following characteristics?

Question

A 56-year-old woman comes to the emergency department because of worsening pain and swelling in her right knee for 3 days. She underwent a total knee arthroplasty of her right knee joint 5 months ago. The procedure and immediate aftermath were uneventful. She has hypertension and osteoarthritis. Current medications include glucosamine, amlodipine, and meloxicam. Her temperature is 37.9°C (100.2°F), pulse is 95/min, and blood pressure is 115/70 mm Hg. Examination shows a tender, swollen right knee joint; range of motion is limited by pain. The remainder of the examination shows no abnormalities. Blood cultures repeatedly grow gram-positive cocci in clusters, which are identified as Staphylococcus epidermidis.  This pathogen most likely demonstrates which of the following characteristics?

Quizplus · Accepted Answer

Eductional Objective: Staphylococcus epidermidis, a gram-positive coccus that grows in clusters, is a skin commensal that is a common cause of infection in patients with prosthetic devices such as artificial joints or heart valves.  Unlike S aureus, S epidermidis is coagulase-negative.  Unlike S saprophyticus (another coagulase-negative staphylococci species), S epidermidis is susceptible to novobiocin.

A 56-Year-Old Woman Comes to the Emergency Department Because of Worsening