Clinical VignetteQuestion 1 of 26
Bubbly Umbilical Clot
A 4-day-old male neonate develops several pustular skin lesions around the umbilicus. A swab from one of the pustules is processed in the microbiology laboratory. The Gram stain reveals gram-positive cocci arranged in grape-like clusters. When hydrogen peroxide is added to a colony on a glass slide, vigorous bubbling is observed immediately. A loopful of the organism is then added to a tube of rabbit plasma and incubated at 37°C; after 4 hours, the plasma has solidified into a firm clot. When the organism is plated onto mannitol salt agar, the colonies are surrounded by a bright yellow halo.
Which of the following organisms is most consistent with these laboratory findings?