What are the appropriate antibiotics (Abx) for the treatment of cellulitis?

From the Guidelines

For cellulitis, first-line antibiotic treatment should include a 5-7 day course of cephalexin 500mg orally four times daily, dicloxacillin 500mg orally four times daily, or clindamycin 300-450mg orally three times daily, as recommended by the most recent guidelines 1.

Key Considerations

• The choice of antibiotic should be based on the severity of the infection and the presence of risk factors for MRSA, such as penetrating trauma, nasal colonization, or injection drug use 1.
• For patients with suspected MRSA, consider adding trimethoprim-sulfamethoxazole (TMP-SMX) 1-2 double-strength tablets twice daily or doxycycline 100mg twice daily to the treatment regimen.
• In more severe cases requiring hospitalization, intravenous options include cefazolin 1-2g every 8 hours, oxacillin 1-2g every 4-6 hours, or vancomycin 15-20mg/kg every 8-12 hours for MRSA coverage.

Additional Recommendations

• Elevate the affected limb to reduce swelling and mark the border of the infection to monitor progression 1.
• Ensure adequate pain control and advise patients to seek immediate medical attention if they develop fever, increasing pain, rapid spread of redness, or systemic symptoms.
• The 2019 National Institute for Health and Care Excellence (NICE) guideline recommends a course of 5 to 7 days, which is supported by recent studies 1.

Important Notes

• The optimal duration of antibiotic therapy for cellulitis is still a topic of debate, but the current evidence suggests that a 5-7 day course is sufficient for most cases 1.
• Further study is needed to evaluate the optimal duration of antibiotic therapy for skin and soft tissue infections, but current guidelines provide a framework for treatment decisions 1.

From the FDA Drug Label

The types of ABSSSI included were cellulitis/erysipelas (41%), wound infection (29%), and major cutaneous abscess (30%) Clinical success by baseline pathogens from the primary infection site or blood cultures for the microbiological intent-to-treat (MITT) patient population for two integrated Phase 3 ABSSSI studies are presented in Table 8 and Table 9 Tedizolid phosphate was tested for genotoxicity, and was also tested for genotoxicity after metabolic activation.

Tedizolid can be used for the treatment of cellulitis as it has shown clinical success in patients with acute bacterial skin and skin structure infections (ABSSSI), including those with cellulitis/erysipelas 2.

• The primary endpoint in Trial 1 was early clinical response defined as no increase from baseline lesion area at 48-72 hours after the first dose and oral temperature of ≤37.6°C.
• Clinical success was defined as resolution or near resolution of most disease-specific signs and symptoms, absence or near resolution of systemic signs of infection if present at baseline.
• Tedizolid has been shown to be effective against various baseline pathogens, including Staphylococcus aureus, Methicillin-resistant S. aureus, and Streptococcus pyogenes 2.

From the Research

Antibiotics for Cellulitis

• The majority of non-purulent, uncomplicated cases of cellulitis are caused by β-hemolytic streptococci or methicillin-sensitive Staphylococcus aureus 3.
• Appropriate targeted coverage of this pathogen with oral antibiotics such as penicillin, amoxicillin, and cephalexin is sufficient for non-purulent cellulitis 3.
• Coverage for non-purulent cellulitis is generally not recommended, even with rising rates of community-acquired methicillin-resistant Staphylococcus aureus 3.

Empiric Antimicrobial Strategies

• Cephalexin is the most cost-effective option for outpatient empiric therapy of cellulitis, given various likelihoods of infection due to MRSA 4.
• Clindamycin becomes a more cost-effective therapy at MRSA probabilities from 41-80% when the probability of staphylococcal infection is greater than 40% 4.
• TMP/SMX is unlikely to be cost-effective for treatment of simple cellulitis 4.

Efficacy and Safety of Antibiotics

• There are no significant differences in cure rates for cellulitis among the antibiotics analyzed, with cefaclor demonstrating the most favorable profile for curative outcomes 5.
• Ceftriaxone is identified as the least likely to induce diarrhea or vomiting 5.
• Pristinamycin shows the most promising results in achieving cure rates for erysipelas, but with a higher risk of rash 5.