Bryan M. Dunn, MD, FACEP

Many people every week come to our Urgent Care Centers with what seems to be a “spider bite.” In virtually all cases, no spider was ever seen and no bite was ever felt. What people almost always report is that they noticed a small bump or lesion that looked like a pimple and over the course of two or three days it became larger and more painful. They frequently relate the story of a friend or family member with the same type of lesion in the recent past, further increasing the suspicion that a silent-assassin ninja spider is attacking friends and family alike. Are these lesions spider bites? In most cases, they are something else.

Since 2004, there has been a nationwide epidemic of CA-MRSA, or Community Acquired Methcillin Resistant Staphy-lococcus Aureus. MRSA is a bacterium which has been present in hospitals and nursing homes for decades. Recently, it has mutated into a form that has now spread throughout the general population. Eight to ten percent of all people are either colonized or are carriers of MRSA. A benign-appearing lesion that becomes red, warm and tender over the course of a few days is highly suspicious for MRSA. No wound, injury or break in the skin is necessary for MRSA to be introduced.

Spider bites, and more specifically, brown recluse spider bites are actually rare occurrences. Most spider bites will be felt and most of the time the attacking spider will be seen. Brown recluse bites many times are minimally painful, but recluse bites very commonly lead to a condition called loxoscelism. Loxoscelism is a flu-like illness with fever, body aches and a rash that occurs soon after envenomation by Loxosceles reclusa, otherwise known as the brown recluse spider. Recluse bites typically do not become infected or lead to pus-filled, draining wounds characteristic of MRSA. Recluse bites are an envenomation, not an infection. Rarely, recluse bites will become necrotic, where the tissue surrounding the bite site will deteriorate and slough away. Treatment is difficult and the lesions commonly take months to heal.

By contrast, MRSA wounds are infections and they are characteristically painful, hard, warm, red areas of the skin that require drainage and frequently, antibiotics. Evaluation by a physician is necessary to determine whether or not incision of the overlying skin and drainage of the infection will be beneficial and part of the treatment plan. Fortunately, adequate drainage and antibiotics are largely successful in treating an MRSA abscess (or boil, as they are sometimes called). There are several oral antibiotics that can treat MRSA infection. If an individual develops recurrences, or if MRSA has been identified in family members or other close contacts, then steps can be taken to help to decrease the degree of MRSA colonization.

Identifying exactly where one contracted MRSA can be almost impossible. However, effective treatment, when sought early, is highly effective. The good news is an exterminator doesn’t have to be called, because spiders aren’t the culprits.

Numerous clumps of methicillin-resistant Staphylococcus aureus bacteria,
commonly referred to by the acronym, MRSA; Magnified 2390x.