Skin and soft tissue infections (SSTIs), also referred to as skin and skin structure infections, are a relatively common reason for health care visits in both the inpatient and outpatient settings.

More than 14 million people present to doctors’ offices and hospital emergency and outpatient departments each year for symptoms related to skin infections.1 Of the 3.5 million emergency department visits for skin infections, 1 in 5 leads to admissions.

SSTIs are classified as nonpurulent and purulent and can be subcategorized as mild, moderate, or severe. Mild infections present with local symptoms only, whereas moderate to severe infections have systemic signs of infection, such as a heart rate higher than 90 beats per minute, respiratory rate higher than 24 breaths/minute, temperature higher than 100.5°F, or white blood cell count higher than 12 × 103 cells/mm3.2

Over the past 2 decades, community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) has emerged as the most common cause of purulent skin infections in the United States. Patients with CA-MRSA report higher rates of complications (eg, abscess), recurrence, and treatment failures that often require hospitalization.

Most SSTIs are caused by bacteria and are referred to as acute bacterial skin and skin structure infections. Of the bacterial skin infections, cellulitis, impetigo, erysipelas, and folliculitis are the most frequently diagnosed, with cellulitis the most common, accounting for 200 cases per 100,000 patient-years.3

Presentation
Cellulitis is an acute infection of the dermis and subcutaneous tissue characterized by advancing borders, edema, and warmth. It mainly occurs near breaks in the skin, such as a cut, surgical wound,orevenaninsectbite. Occasionally,cellulitis presents in skin that appears normal. Athlete’s foot, chronic leg swelling, eczema, impetigo, and psoriasis can predispose an individual to cellulitis.

The most common cause of cellulitis is β-hemolytic streptococci, usually group A Streptococcus or Streptococcus pyogenes and S aureus (including methicillin-resistant strains).4 Gram-negative aerobic bacilli are identified in a minority of cases.

The signs and symptoms associated with cellulitis are a result of pathogenic microorganisms invading and causing damage to surrounding tissue, which leads to an inflammatory response characterized by edema, erythema, pain, and warmth. The most common sites of cellulitis are the arm, head, neck, and lower leg, though it can appear anywhere on the body. Some sites are further categorized by their location, such as buccal, facial, or periorbital cellulitis.

Patients with diabetes and those undergoing chemotherapy or receiving drugs that suppress the immune system are more susceptible to developing cellulitis, as are the elderly or anyone with a weakened immune system.

Do Not Jump to Conclusions
All that is red is not always cellulitis. A recent cross-sectional study found that 31% of patients hospitalized with cellulitis had misdiagnosed cases.1,5 The conditions that most likely looked like cellulitis were stasis dermatitis, stasis ulcers, gout, congestive heart failure, nonspecific edema, and deep venous thrombosis.5

Furthermore, when clinicians specifically consulted dermatologists because of uncertainty about a diagnosis of cellulitis, 74% of the patients turned out to have a form of pseudocellulitis, not cellulitis.6 In the same study, dermatologists were able to tailor care and discharge unnecessary admits, saving both cost and resources.6

Because many conditions can present like cellulitis and no diagnostic tools are available, history and physical examination are the most useful ways to diagnose uncomplicated cellulitis. Diagnosis should evaluate the infection’s cause and severity, and treatment must account for local antibiotic resistance and pathogen-specific patterns.1,4

Keep Tabs During Treatment
More than 90% of patients with mild cellulitis can be effectively managed with oral antibiotics in the outpatient setting. Patients with no abscess and nonpurulent cellulitis should be treated with empiric therapy for infection to cover β-hemolytic streptococci and methicillin-susceptible S aureus.4,7,8 Antibiotics such as cephalexin, clindamycin, dicloxacillin, and penicillin V potassium are usually effective first-line treatments.4,7,8

If an outpatient on oral therapy has not improved within 48 to 72 hours, the provider may need to reassess the condition and determine if skin culture or treatment modification is necessary. Hospitalization and intravenous antibiotics are sometimes required if oral antibiotics are not effective. If not properly managed, cellulitis can spread to the bloodstream and cause sepsis.

Additional empiric coverage for MRSA should be considered in the following circumstances4:
  • Known colonization or prior episode of MRSA
  • Lack of clinical response to antibiotic regimen that does not include activity against MRSA
  • Presence of risk factor(s) for MRSA infection, including hemodialysis, HIV infection, recent hospitalization, recent surgery, and residence in a long-term-care facility
  • Proximity of the lesion to an indwelling medical device (eg, prosthetic joint or vascular graft)
  • Systemic signs of toxicity (eg, fever >100.5°F, hypotension, or tachycardia)
In these cases and in patients with purulent infections, antibiotics such as clindamycin, tetracyclines, and trimethoprim-sulfamethoxazole, with a treatment duration of 5 to 14 days, depending on the severity, would be appropriate.Delafloxacin, linezolid, omadacycline, and tedizolid also have MRSA coverage, but these antibiotics should be reserved for when other treatment options cannot be used.

Know the Counseling Points
Patients present to community pharmacies and outpatient clin- ics all the time to pick up antibiotics and/or with symptoms of skin infections. Pharmacists should be ready to counsel on antibiotic therapy and duration, wound care, and when to call their doctor for further evaluation.

Patients should call their doctor’s office or seek evaluation if they have any of the following:
• Cellulitis with surrounding fluctuant, soft areas that suggest abscess formation
• Fever (>100.5°F), especially when associated with chills
• Inability to move an extremity or joint because of pain
• Red streaking from an area of cellulitis or a fast-spreading area of redness, which indicates that the infection may need a different antibiotic, closer observation, or inpatient supportive care
• Significant pain not relieved by acetaminophen or ibuprofen

Pharmacists should be familiar with the presentation and treatment for common skin infections. As frontline professionals, many pharmacists face skin infections almost daily. Although we cannot diagnosis or prescribe, our expertise is relied on often in ambulatory and hospital settings to help patients discern the severity and when a doctor’s visit is warranted.

REFERENCES
  1. Kaye KS, Petty LA, Shorr AF, Zilberberg MD. Current epidemiology, etiology, and burden of acute skin infections in the United States. Clin Infect Dis. 2019;68(suppl 3): S193-S199. doi: 10.1093/cid/ciz002.
  2. Anaya DA, Dellinger EP. Necrotizing soft-tissue infection: diagnosis and management. Clin Infect Dis. 2007;44(5):705-710. doi: 10.1086/511638.
  3. Ellis Simonsen SM, van Orman ER, Hatch BE, et al. Cellulitis incidence in a defined population. Epidemiol infect. 2006;134(2):293-299. doi: 10.1017/S095026880500484X.
  4. Stevens DL, Bisno AL, Chambers HF, et al. Practice guidelines for the diagnosis and management of skin and soft tissue infections: 2014 update by the Infectious Diseases Society of America. Clin Infect Dis. 2014;59(2):147-59. doi: 10.1093/cid/ciu296.
  5. Weng QY, Raff AB, Cohen JM, et al. Costs and consequences associated with misdiagnosed lower extremity cellulitis. JAMA Dermatol. 2017;153(2):141-146. doi: 10.1001/ jamadermatol.2016.3816.
  6. Strazzula L, Cotliar J, Fox LP, et al. Inpatient dermatology consultation aids diagnosis of cellulitis among hospitalized patients: a multi-institutional analysis. J Am Acad Dermatol. 2015;73(1):70-75. doi: 10.1016/j.jaad.2014.11.012.
  7. Liu C, Bayer A, Cosgrove SE, et al; Infectious Diseases Society of America. Clinical practice guidelines by the Infectious Diseases Society of America for the treatment of methicillin-resistant Staphylococcus aureus infections in adults and children. Clin Infect Dis. 2011;52(3):e18-e55. doi: 10.1093/cid/ciq146.
  8. Raff A, Kroshinsky D. Cellulitis: a review. JAMA. 2016;316:325-337. doi: 10.1001/ jama.2016.8825.