What is a suitable antibiotic to initiate treatment for cellulitis?

From the Guidelines

For uncomplicated cellulitis, a 5- to 6-day course of antibiotics active against streptococci, such as cephalexin 500 mg orally four times daily, is a good initial choice. This recommendation is based on the most recent and highest quality study available, which suggests that a shorter course of antibiotics may be effective for treating uncomplicated cellulitis 1. Alternatives to cephalexin include dicloxacillin 500 mg orally four times daily, clindamycin 300-450 mg orally three times daily (especially for penicillin-allergic patients), or trimethoprim-sulfamethoxazole (TMP-SMX) DS tablet twice daily if MRSA is suspected. The choice of antibiotic depends on local resistance patterns and patient factors, such as the presence of penetrating trauma, evidence of MRSA infection, or systemic inflammatory response syndrome.

Some key points to consider when treating cellulitis include:

• The importance of covering streptococci, as they are a common cause of cellulitis
• The potential need for MRSA coverage in certain cases, such as those with penetrating trauma or evidence of MRSA infection
• The use of a 5- to 6-day course of antibiotics, as recommended by the American College of Physicians 1
• The importance of monitoring patients for signs of worsening infection, such as spreading redness, increasing pain, fever, or red streaking, and adjusting treatment as needed.

It's also important to note that the 2019 National Institute for Health and Care Excellence (NICE) guideline recommends a course of 5 to 7 days of antibiotics for uncomplicated cellulitis 1. However, the more recent study from 2021 suggests that a 5- to 6-day course may be sufficient 1. Overall, the choice of antibiotic and duration of treatment should be individualized based on patient factors and local resistance patterns.

From the FDA Drug Label

Clindamycin is indicated in the treatment of serious infections due to susceptible strains of streptococci, pneumococci, and staphylocci... Serious skin and soft tissue infections; septicemia; intra- abdominal infections... infections of the female pelvis and genital tract such as endometritis, nongonococcal tubo-ovarian abscess, pelvic cellulitis For cellulitis, a good antibiotic to start may be clindamycin (PO), as it is indicated for the treatment of serious skin and soft tissue infections, including pelvic cellulitis 2.

• Key points:
  • Clindamycin is effective against susceptible strains of streptococci, pneumococci, and staphylococci
  • It is indicated for serious skin and soft tissue infections, including pelvic cellulitis
  • Bacteriologic studies should be performed to determine the causative organisms and their susceptibility to clindamycin

From the Research

Antibiotic Treatment for Cellulitis

• The choice of antibiotic for cellulitis depends on various factors, including the severity of the infection and the presence of methicillin-resistant Staphylococcus aureus (MRSA) 3.
• A study published in 2010 found that trimethoprim-sulfamethoxazole and clindamycin were effective empiric therapies for outpatients with cellulitis in areas with a high prevalence of community-associated MRSA infections 3.
• However, a randomized controlled trial published in 2013 found that the addition of trimethoprim-sulfamethoxazole to cephalexin did not improve outcomes in patients with uncomplicated cellulitis 4.
• Another study published in 2017 found that the use of cephalexin plus trimethoprim-sulfamethoxazole compared to cephalexin alone did not result in higher rates of clinical resolution of cellulitis in the per-protocol analysis, but the modified intention-to-treat analysis suggested a possible benefit 5.
• A systematic review and meta-analysis published in 2020 found no evidence of difference in clinical response rates for antibiotic route or duration, and highlighted the need for patient-tailored antibiotic prescribing to reduce unnecessary antibiotic use 6.
• A systematic review and meta-analysis published in 2019 found that there is low-quality evidence to support the use of any particular antibiotic, route of administration, or duration of treatment for cellulitis, and emphasized the need for future trials to use standardized outcomes 7.

Key Findings

• Trimethoprim-sulfamethoxazole and clindamycin may be effective empiric therapies for outpatients with cellulitis in areas with a high prevalence of community-associated MRSA infections 3.
• The addition of trimethoprim-sulfamethoxazole to cephalexin may not improve outcomes in patients with uncomplicated cellulitis 4, 5.
• There is a need for patient-tailored antibiotic prescribing to reduce unnecessary antibiotic use 6.
• Future trials should use standardized outcomes, including severity scoring, dosing, and duration of therapy 7.