Cellulitis Antibiotic Selection: Management Updates

Authors: Josh Bucher, MD (Assistant Professor of Emergency Medicine, Rutgers – RWJMS) and Darren Cuthbert, MD, MPH (EM Resident Physician, Rutgers – RWJMS) // Edited by: Alex Koyfman, MD (@EMHighAK, EM Attending Physician, UTSW / Parkland Memorial Hospital) and Brit Long, MD (@long_brit, EM staff physician at SAUSHEC, USAF)

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The treatment of cellulitis has changed tremendously in the last ten years. With the development of community-acquired MRSA infections along with an increasing number of immunocompromised hosts, there is concern about missing MRSA if not treating cellulitis for it.1 However, the Infectious Disease Society of America (IDSA) released their skin and soft tissue guidelines in 2014, providing clear instructions for both antibiotic choice and who should be treated for suspected MRSA. We will start with four cases and then describe the IDSA recommendations.

These cases will highlight the recent updates to the Infectious Disease Society’s Practice Guidelines for the management of cellulitis and soft tissue infections. It is vital that emergency providers stay current with their clinical judgment in disposition as well as the use of appropriate antibiotic therapy.



Case 1 – A 47 year-old Hispanic male with a history of poorly controlled type II diabetes mellitus presents to your ED complaining of pain with redness to the distal posterior leg.  He reports an onset of 1 week with the pain progressively worsening while the area has quadrupled in size. He denies recollection of a triggering event.  He describes his pain as throbbing in quality, worsening from 1/10 at first instance, to 5/10 today, non-radiating, with mild exacerbation upon light touch and ambulation.  The patient has spent the past month living in a homeless shelter while in recovery for alcoholism. He has no primary doctor.   Visual inspection reveals a right leg with a 10” by 8” area that is red, warm, and erythematous, with sharply demarcated borders. The area is tender to touch with a negative Pratt’s or Homan’s sign.  His leg has adequate distal pulses, with no motor or sensory deficits.  He has no fever, chills, and his vital signs are within normal limits. A bedside ultrasound performed shows no fluid collection.

Case 2 – A 28 year-old Caucasian female with a 9-year history of intravenous heroin use presents to your ED complaining of fever and pain with redness to the right antecubital space. The patient states she first noticed redness surrounding an injection site 3 days prior, but continued to inject within that proximity. Yesterday she was unable to find a vein and noticed pus oozing from the site.  Over the past 24 hours the area has become more painful, and she feels what she describes as a “ball” underneath the skin within the region. Visual inspection shows a poorly demarcated area of redness in the right antecubital space that is circumferential around the elbow, spreading half way down the forearm.  The area is warm and tender to light touch, spanning approximately 4.5” by 7”. There is a smaller area in the middle with fluctuance and induration. Her temperature is 101.6, with a blood pressure and heart rate of 102/55 and 103, respectively.  She has adequate distal pulses, with no motor or sensory deficits.

Case 3 – A 25 year-old health male presents with the complaint of flank pain. He reports he scraped it a few days ago inside his house. He cleaned it, but it has progressively became more painful. On exam, he has a 4 x 4 cm area of erythema that is tender without crepitus. He is afebrile, has no medical problems, and has an appointment with his primary doctor in two days but could not wait due to pain so came in for evaluation today.

Case 4 – A 66 year-old patient with an aggressive leukemia presents with altered mental status. He last received chemotherapy 3 days ago. His family stated he has become progressively confused and noted a weird rash. On his left lower extremity there is erythema, purple discoloration, and large bullae up to the proximal thigh. He is febrile, tachycardia, and hypotensive. His sodium is 127 and his WBC is 35.


When approaching the management of skin in soft tissue infections in the ED, it must first be determined whether the infection is purulent or non-purulent, followed by assessing the severity.  Non purulent infections vary in form from erysipelas and cellulitis.  Purulently draining skin and soft tissue infections usually come in the form of furuncles, carbuncles, or abscesses.1 Feasibility and specification of antibiotic use, need for surgical evaluation, and need for culture and sensitivity are all dependent upon these factors.

Distinguishing the mild purulent skin and soft tissue infection from a moderate or severe infection begins with the physical exam and vital signs.  Both the moderate and severe cases show signs of systemic disease.1 In the case of skin and soft tissue infections, systemic disease is defined as a temperature >38C, tachycardia >90 bpm, respiratory rate >24, or an abnormal white blood cell count >12,000 or < 4,000.  Immunocompromised patients are also considered as having systemic disease.  A severe patient is one with systemic disease who has failed a round of antibiotic therapy or incision and drainage.1 Non-purulent infection severity is defined similarly, but rather than failing incision and drainage, which isn’t indicated for non-purulent cellulitis, a severe infection demonstrates deeper spread and systemic signs of sepsis including hypotension and other organ dysfunction.1

If no focal purulence is found, incision and drainage is not indicated, while antibiotics are.  Mild and moderate cases in a stable patient can be managed as an outpatient, with no culture and sensitivity required.  A beta-lactam, cephalosporin (with sea water exposure), or clindamycin is efficacious per the IDSA.1 Many treatment plans will depend on institution sensitivities and antibiogram, so if possible utilize these helpful resources.

In the case of a severe non-purulent infection, a necrotizing process must be ruled out.1  Necrotizing fasciitis comes in three forms: type I which is polymicrobial (most common), type II which typically occurs on the extremities and is caused by a Group A streptococcus, and type III which is caused by vibrio vulnificus via underwater sea injury.2 The most important risk factor for necrotizing fasciitis is a weakened immune system such as diabetes, cancer, or HIV.2  Suspicion for necrotizing fasciitis requires immediate surgical inspection in conjunction with empiric antibiotics (vancomycin plus piperacillin/tazobactam and clindamycin).1 The patient requires ICU admission and empiric antibiotics, along with surgical debridement.1

Purulent skin and soft tissue infections on the other hand require incision and drainage; in fact, a mild infection only requires incision and drainage without culture/sensitivity or antibiotic therapy.  Moderate and severe disease are treated with empiric antibiotics (TMP/SMX or doxycycline in moderate disease, or vancomycin or daptomycin in severe disease) pending the results of a culture and sensitivity.1


Case Resolutions

Case 1 – The patient is unable to obtain any outpatient follow up as he is homeless with no primary doctor. The patient agrees with the plan for admission for intravenous antibiotics, and 1 gram of cefazolin is ordered.

Case 2 – The abscess is incised with greater than 20 mL of purulent fluid expressed from the wound. An appropriate weight-based dose of vancomycin is administered, and the patient is admitted.

Case 3 – The patient is appropriately treated in the mild, non-purulent category and leaves with a prescription for penicillin VK for one week.

Case 4 – Emergent surgical consultation is obtained. The patient is administered vancomycin, piperacillin/tazobactam as well as clindamycin, and the surgical service takes the patient to the operating room for an obvious necrotizing infection.


Take Home Points

  1. Patients with uncomplicated cellulitis, with no co-morbidities, and without purulence, require coverage for MSSA with penicillins or first-generation cephalosporins.
  2. Patients with non-purulent cellulitis requiring admission only need coverage for MSSA and not MRSA.
  3. Purulent cellulitis requires coverage for MRSA.
  4. Necrotizing fasciitis requires broad-spectrum coverage, and, most importantly, immediate surgical consultation for debridement.
  5. Know your hospital’s antibiogram and availability of timely outpatient follow-up.


References / Further Reading

  1. Stevens D.L., Bisno A.L., et al. (2014). Practice Guidelines for the Diagnosis and Management of Skin and Soft Tissue Infections: 2014 Update by the Infectious Diseases Society of America. Infectious Diseases Society of America: Clinical Infectious Diseases Advance Access, June 18th, 2014. (1). DOI: 10.1093/cid/ciu296
  2. Babak S., Strong M., Pascual J., Schwab W. (2009). Necrotizing Fasciitis: Current Concepts and Review of the Literature. Journal of the American College of Surgeons. 208-2 (279-288). DOI: http://dx.doi.org/10.1016/j.jamcollsurg.2008.10.032

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