A purulent skin lesion after a spider bite is most likely caused by which organism?

• A. MRSA
• B. Staphylococcus aureus (MSSA)
• C. Streptococcus pyogenes
• D. Pseudomonas aeruginosa

Answer: (A)

Purulent skin lesions come from pus-forming infections, and Staphylococcus aureus is the typical organism that creates abscesses and boils. A spider bite disrupts the skin barrier, giving bacteria an entry point, and S. aureus is a common skin colonizer that can establish a focal purulent infection. In many communities today, the methicillin-resistant strain of S. aureus (MRSA) is a leading cause of these purulent skin and soft tissue infections, making it the most likely culprit after a spider bite.

Streptococcus pyogenes more often causes nonpurulent cellulitis, while Pseudomonas is associated with specific settings like hot tub exposure or certain wound types, not the classic purulent lesion after a spider bite.