This tissue gram stain of an acute pneumonia demonstrates dark purple dot-like gram positive cocci that have been eaten by the numerous PMN's exuded into the alveolar space. Opsonins such as IgG and C3b facilitate the attachment of PMN's to offending agents such as bacteria so that the PMN's can phagocytose them. An elevated serum procalcitonin level is a marker of severe sepsis.

Question: What organisms may be implicated?

AnswerCommon gram positive cocci causing pneumonia include streptococci (Streptococcus pneumoniae, Enterococcus) and Staphylococcus aureus.