What is the common cause of cellulitis and its treatment?

From the Guidelines

Cellulitis is most commonly caused by bacterial infections, particularly those involving Streptococcus and Staphylococcus bacteria, which enter the skin through cuts, cracks, or other breaks in the skin barrier. The treatment of cellulitis typically involves oral antibiotics such as cephalexin (500 mg four times daily), dicloxacillin (500 mg four times daily), or clindamycin (300-450 mg three times daily) for 5-10 days for mild to moderate cases 1.

Key Considerations

• For more severe infections, hospitalization may be necessary for intravenous antibiotics like vancomycin, ceftriaxone, or piperacillin-tazobactam.
• In addition to antibiotics, patients should elevate the affected area, apply warm compresses, take pain relievers as needed, and keep the area clean and dry.
• It's essential to complete the full course of antibiotics even if symptoms improve quickly.
• If MRSA (methicillin-resistant Staphylococcus aureus) is suspected, alternative antibiotics like trimethoprim-sulfamethoxazole (one double-strength tablet twice daily) or doxycycline (100 mg twice daily) may be prescribed 1.
• Cellulitis requires prompt treatment to prevent the infection from spreading deeper into the tissue or bloodstream, which could lead to more serious complications.

Treatment Guidelines

• The Infectious Diseases Society of America recommends empirical therapy for CA-MRSA in outpatients with purulent cellulitis and for infection due to b-hemolytic streptococci in outpatients with nonpurulent cellulitis 1.
• For hospitalized patients with complicated SSTI, empirical therapy for MRSA should be considered pending culture data, with options including intravenous vancomycin, linezolid, daptomycin, telavancin, or clindamycin 1.

Prevention of Complications

• Elevation of the affected area and keeping it clean and dry can help prevent the spread of infection.
• Patients should be monitored for signs of systemic illness, such as fever, tachycardia, and hypotension, and for local signs of infection, such as increased redness, swelling, and pain.
• If MRSA is suspected, patients should be isolated to prevent the spread of infection to others.

From the Research

Causes of Cellulitis

• The common causes of cellulitis are group A streptococci (Streptococcus pyogenes) and Staphylococcus aureus, including community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) 2, 3, 4.
• However, the role of CA-MRSA in nonpurulent cellulitis is less clear, and some studies suggest that it plays only a minor role in nonpurulent cellulitis 2.
• Methicillin-susceptible S. aureus was detected in some studies, but methicillin-resistant S. aureus or S. pyogenes were not found by culture or PCR in other studies 5.

Treatment of Cellulitis

• The treatment of cellulitis usually involves empiric antimicrobial therapy, with antibiotics such as cephalexin, trimethoprim-sulfamethoxazole, and clindamycin being commonly prescribed 2, 3.
• The choice of antibiotic depends on the severity of the infection, the presence of risk factors for treatment failure, and the prevalence of CA-MRSA in the community 3.
• Some studies suggest that antibiotics with activity against community-associated MRSA, such as trimethoprim-sulfamethoxazole and clindamycin, are preferred empiric therapy for outpatients with cellulitis in the community-associated MRSA-prevalent setting 3.
• Accurate diagnosis and subsequent management with the narrowest possible antimicrobial therapy is ideal both for individual patient outcomes and for public health 4.

Diagnosis of Cellulitis

• The diagnosis of cellulitis remains largely clinical, and evaluation by a dermatologist and/or infectious disease specialist continues to be the clinical gold standard 4.
• There is no gold standard diagnostic test for cellulitis, as laboratory assessments, tissue and blood cultures, and imaging studies have not been helpful 4.
• Adjunctive studies, such as thermal imaging, may be useful for ruling out mimickers or more serious or complicating conditions, such as osteomyelitis, necrotizing fasciitis, or abscess 4.