Case: I have a bite
Case Study: The Phantom “Spider Bite”
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“Three days ago I developed this really gross infection on my knee from a spider bite. I went to the Emergency Department and they gave me an antibiotic. It’s getting worse. Can you help?”
Case: Dylan is a 16-year old boy presenting to your office for follow-up of a swollen left knee that started several days ago. He was diagnosed with a patellar cellulitis and sent home on a cephalosporin 3 times daily. He now complains of a worsening abscess and left groin pain.
His medical history is unremarkable for allergies, injuries, or surgeries. He is a wrestler on his high school team and travels frequently for meets. He spent last weekend at a team camp-out in the woods and recently helped his dad restack the woodpile. He denies seeing any ticks, ants, or spiders, but thinks he may have felt a small ‘sting’ on his leg.
Social History: Patient is a healthy 16-year-old boy living in New England with his parents and 2 siblings. No history of allergies or skin diseases. Takes no medications and is the captain of his high school wrestling team. He loves being outdoors and is an avid camper and fisherman. He is up to date with all his immunizations.
Physical Examination:
Height 61”, weight 183 lbs. BP 115/75. Temperature 98.9°F
Review of Systems: WNL
Extremeties: Tender warm red patellar abscess with painful erythematous nodule and 2 x 3 cm cellulitis of the adjacent tissue. He has full range of motion of the knee. A tender 2-cm lymph node was palpable in his left groin.
How would you proceed?
Published on June 15, 2010
Updated on June 22, 2010
Discussion
While Dylan’s symptoms might appear to be the result of a spider bite, it is far more likely that a culture will reveal community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA). In fact, more than 75% of patients presenting with soft-tissue infections are found to have CA-MRSA on culture and many of these patients attribute the infection to spider bites—even in areas of the country where spiders capable of causing necrotic skin lesions are not endemic.[1] In almost every case, no spider is seen biting or is collected in the incident. CA-MRSA refers to an MRSA infection in an individual without established hospital-acquired MRSA risk factors, such as recent hospitalization, surgery, residence in a long-term care facility, or kidney dialysis.
Factors that have been associated with the spread of MRSA skin infections include close skin-to-skin contact, crowded living conditions, and skin cuts and abrasions. According to statistics from the Centers of Disease Control and Prevention, the risk for CA-MRSA is highest in athletes, prison inmates, military personnel, and children in daycare.[2] Dylan’s active participation and travel with the wrestling team is the likely source of his infection.The most frequently reported clinical manifestations of skin and soft tissue infections include furuncles, carbuncles, and abscesses.
Treatment
The primary indicated treatment for CA-MRSA abscess is incision and drainage (I&D). In fact, many patients will respond to I&D alone without any antibiotic therapy and some data suggest that there is no significant difference between patients who receive an antibiotic versus those who do not.[3]
Larger purulent skin lesions may require empiric antimicrobial therapy in addition to I&D. Beta-lactams like Dylan received (including penicillins and cephalosporins, and all flouroquinolones) should be avoided as first-line single drug therapy. Unlike hospital acquired MRSA, most CA-MRSA isolates are still susceptible to trimethoprim-sulfamethoxazole (TMP/SMX; Bactrim), gentamicin, tetracycline, and clindamycin. However, in various geographical areas throughout the United States, clindamycin is showing resistance trends. Treatment with TMP/SMX is a good choice and is especially successful in children. It is also relatively inexpensive. Since sulfamethoxazole contains sulfa, take care in prescribing it for patients with a sulfa allergy. The most effective dosage for treating MRSA is 10 mg/kg/day based on the trimethoprim component. This is equivalent to 2 double-strength tablets twice daily—double the strength typically used to treat urinary tract infections.[4] TMP/SMX is not advisable by itself if group A streptococci infection is also being considered in which case a second drug such as a beta-lactam should be added. Linezolid use should be severely limited due to its cost and toxicity.
Parental therapy should be considered in the presence of systemic signs such as fever or extensive disease, poor response to oral therapy, and in patients with diabetes or other causes of immune deficiency.
References
- Dominguez TJ. It’s not a spider bite, it’s community-acquired methicillin-resistant Staphylococcus aureus. J Am Board Fam Med. 2004;17(3):220-236.
- Community-associated MRSA information for clinicians. Centers for Disease Control and Prevention Web site. http://www.cdc.gov/ncidod/dhqp/ar_mrsa_ca_clinicians.html#5. Updated February 3, 2005. Accessed June 7, 2010.
- Elston DM. Community-acquired methicillin-resistant Staphylococcus aureus. J Am Acad Dermatol. 2007;56(1):1-16.
- Ellis MW, Lewis, JS II. Treatment approaches for community-acquired methicillin-resistant Staphylococcus aureus infections. Curr Opin Infect Dis. 2005;18(6):496-501.
admit pt to hospital and begin iv antibiotics, ones that are effective against mrsa. Labs: cultures and sensitivity, sed rate, cbc. I and D if area was fluccunet in center of abscess.
I agree with vernon smith. Admit to hospital. Start IV Antibiotics . Send wound for C& S, CBC, I and D if appropriate. Surprised he does not have a fever.
Community acquired MRSA is certainly a consideration as it is prevelant among athetes. Is he sexually active? Can’t tell by the image if the knee if the right or the left.
Community acquired MRSA is certainly a consideration as it is prevelant among athetes. Is he sexually active? Can’t tell by the image if the knee if the right or the left.
I do agree with all. Hwe has failed out-patient therapy with oral antibiotics and needs Iv antibiotics,most likely has MRSA.Vancomycin would be a good choice
Must think about sexual activity which means DGI which needs hospitalization. Along with discussing partners, as DGI is most always ASX.
And yes MRSA should be considered.
Brown recluse spider bites frequently present as above, not responding to cephalosporins. Is there any necrotic tissue? pain?, MRSA also may complicate the picture as it is in the differential. Would hospitalize and have ID take alook. Last Tetanus?
We know that Bactrim DS bid can be used as first line for Tx of MRSA. Based on complicated skin, soft tissue infection I will considere Linezolide 600 mg q 12 hrs ivpb or Clindamycine ( efficacity 92%).
Hope someone will replay to my thought.
Thanks.