A gram-positive cocci in clusters most consistently indicates which organism, commonly found on human skin and capable of causing impetigo?

• A. Staphylococcus aureus
• B. Streptococcus pyogenes
• C. Staphylococcus epidermidis
• D. Enterococcus faecalis

Answer: (A)

Gram-positive cocci in clusters point to a Staphylococcus species. On human skin, the most common and virulent member that causes impetigo is Staphylococcus aureus. It routinely colonizes skin and nares and, with its toxins and enzymes, can invade superficial skin to produce the characteristic honey-crusted lesions of impetigo. Other options either form clusters but are less virulent and more associated with foreign-body infections (Staphylococcus epidermidis), or they present as chains rather than clusters (Streptococcus pyogenes), or are primarily gut-associated organisms (Enterococcus faecalis). Thus, the organism most consistent with this presentation is Staphylococcus aureus.