Cellulitis: On the lookout for infiltration
Cellulitis is a bacterial infection of the skin that affects approximately 24.6 in 1000 people and is rarely associated with death.21 It occurs when bacteria enter through disrupted areas in the skin, particularly when skin integrity is compromised by recent surgery, piercing, wounds, athlete’s foot, or even dermatitis.22,23Streptococcus and Staphylococcus are the 2 most common infectious agents, and methicillin-resistant Staphylococcus aureus (MRSA) is increasingly common.22,23
Although cellulitis is primarily superficial in nature, it may progress to a serious condition by infiltrating underlying tissues and spreading to nearby lymphatic tissue and the bloodstream to cause lymphadenitis or bacteremia.21,23 In instances of cellulitis-induced bacteremia, mortality rates increase if prompt, targeted treatment is not provided.23
Raised erythematous plaques are the cardinal features of cellulitis, with the affected areas warm to the touch, red, and tender.21,23 As the condition progresses, the affected area tends to enlarge and expand (FIGURE 2),24 and the patient often becomes febrile.22,24
The risk of developing cellulitis increases with age, compromised immune status, diabetes, obesity, IV drug use, lymphedema, and chronic corticosteroid use.22,24
Cellulitis is often diagnosed solely on the basis of clinical presentation, although aspiration of purulent discharge from the wound and a gram stain of the culture can confirm the diagnosis.25,26 (See “Is it cellulitis or stasis dermatitis?”.)
Direct immunofluorescence can be used when cultures are difficult to obtain, but this technique is seldom necessary.22 If infiltration of underlying soft tissues is suspected based on clinical findings, magnetic resonance imaging can be a useful tool in evaluating the extent of the infection and in directing appropriate debridement and drainage of affected areas.22,27
Is it cellulitis or stasis dermatitis?
Patients with venous insufficiency may present with stasis dermatitis, which often results in breakdown of the skin and ulceration that bears a striking resemblance to cellulitis. Thus, these conditions can be easily confused, and may lead to unnecessary antibiotic use and, possibly, hospitalization in patients with venous insufficiency.26,28
Despite the similarities of these conditions, a focused patient history and physical exam can prevent such confusion. Stasis dermatitis arises as a result of venous insufficiency, so it is likely to be accompanied by pitting edema that responds to leg raising and to the use of elastic compression stockings—interventions that are seldom effective for cellulitis.26 In addition, cellulitis tends to be unilateral, while stasis dermatitis often has bilateral involvement.
FIGURE 2
Diagnosing cellulitis based on clinical presentation
The raised erythematous lesions that are a hallmark of cellulitis, shown here on the arm and face, are warm to the touch, red, and tender.
Treatment: Targeted antibiotics and preventive measures
Because of the likelihood of recurrence with cellulitis, treating the condition involves both preventive and curative measures. Mild cases can be treated in an outpatient setting with a 7- to 10-day course of oral cephalosporins or antibiotics with similar coverage.22,25,26 A recent randomized study involving 391 patients found that cure rates for cellulitis treated with cephalexin were between 83% and 92%, depending on the pathogen involved.26
For severe cases of cellulitis, patients who are immunocompromised, and cases that are refractory to oral medications, hospital admission is recommended, and use of IV antibiotics is routinely required.22,25,26 For patients with MRSA, a drug such as vancomycin IV may be warranted; a reasonable dose would be 15 mg/kg every 12 hours.22,26,27,29
A recent randomized, multicenter study demonstrated that vancomycin effectively treated approximately 67% of cases of MRSA-induced cellulitis.26 Neomycin should be strictly avoided whenever cellulitis is suspected, because of its propensity to promote antibiotic resistance to S. aureus.29
Patient education emphasizing preventive measures is critical for minimizing recurrence of cellulitis.22,25,26 Encourage patients to wash with antibacterial soap and water daily, apply topical antibiotic ointment, and keep the wound completely covered at all times. Advise them to change bandages and wash their hands frequently.27,29 Patients with diabetes and others with decreased circulation in the extremities need to take further precautions, such as moisturizing the skin regularly in order to prevent cuts in their skin.22,29