What are the recommended antibiotics for perianal cellulitis (inflammation of the skin and subcutaneous tissues)/phlegmon (collection of pus in the subcutaneous tissue)?

From the Guidelines

For perianal cellulitis or phlegmon, empiric antibiotic therapy should include coverage for mixed aerobic and anaerobic bacteria, with a recommended regimen being amoxicillin-clavulanate 875/125 mg orally twice daily for 7-10 days, as supported by the most recent guidelines 1. The choice of antibiotic is crucial in managing perianal cellulitis or phlegmon, as these infections can be caused by a variety of bacteria, including Escherichia coli, Bacteroides species, Enterococcus, and other enteric bacteria.

• The recommended regimen of amoxicillin-clavulanate provides broad-spectrum coverage against these pathogens.
• Alternatives to amoxicillin-clavulanate include clindamycin 300-450 mg orally four times daily, or a combination of ciprofloxacin 500 mg twice daily plus metronidazole 500 mg three times daily for the same duration.
• For more severe infections requiring intravenous therapy, options include piperacillin-tazobactam 3.375 g IV every 6 hours, ampicillin-sulbactam 3 g IV every 6 hours, or ceftriaxone 1-2 g IV daily plus metronidazole 500 mg IV every 8 hours, as suggested by guidelines for complicated skin and soft tissue infections 1. In addition to antibiotics, supportive care such as warm sitz baths 2-3 times daily can help reduce inflammation and pain.
• If an abscess is present, surgical drainage is essential as antibiotics alone are insufficient.
• Patients should maintain good perianal hygiene, use gentle cleansing after bowel movements, and follow up if symptoms worsen or fail to improve within 48-72 hours of treatment, emphasizing the importance of monitoring and adjusting treatment as necessary 1.

From the FDA Drug Label

The two trials were similar in design but differed in patient characteristics, including history of diabetes and peripheral vascular disease There were a total of 534 adult patients treated with daptomycin for injection and 558 treated with comparator in the two trials. Patients could switch to oral therapy after a minimum of 4 days of IV treatment if clinical improvement was demonstrated. Table 15 Investigator’s Primary Diagnosis in the cSSSI Trials in Adult Patients (Population: ITT) Primary DiagnosisAdult Patients (Daptomycin for Injection / Comparator*)

• Comparator: vancomycin (1 g IV every 12h) or an anti-staphylococcal semi-synthetic penicillin (i.e., nafcillin, oxacillin, cloxacillin, or flucloxacillin; 4 to 12 g/day IV in divided doses). Wound Infection 99 (38%) / 116 (44%) Major Abscess 55 (21%) / 43 (16%) Ulcer Infection 71 (27%) / 75 (28%) Other Infection† 39 (15%) / 32 (12%)

The recommended antibiotics for perianal cellulitis/phlegmon are vancomycin or an anti-staphylococcal semi-synthetic penicillin (such as nafcillin, oxacillin, cloxacillin, or flucloxacillin) as comparators to daptomycin, based on the provided drug label information 2.

• Vancomycin: 1 g IV every 12h
• Anti-staphylococcal semi-synthetic penicillin: 4 to 12 g/day IV in divided doses Key points:
• The drug label does not explicitly mention perianal cellulitis/phlegmon, but it does mention complicated skin and skin structure infections (cSSSI), which may include perianal cellulitis/phlegmon.
• The efficacy of daptomycin was compared to vancomycin and anti-staphylococcal semi-synthetic penicillins in the treatment of cSSSI.
• The clinical success rates in the ITT population were similar between daptomycin and the comparators.

From the Research

Recommended Antibiotics for Perianal Cellulitis/Phlegmon

• The recommended antibiotics for perianal cellulitis/phlegmon are not directly mentioned in the provided studies. However, based on the information available, the following antibiotics may be considered:
  • Ampicillin-sulbactam, ceftriaxone, metronidazole, clindamycin, amoxicillin, amoxicillin-clavulanate, cefuroxime, and vancomycin are often used in the treatment of infections such as orbital and preseptal cellulitis 3
  • Amoxycillin/clavulanate (Augmentin) has been shown to be effective in the treatment of severe staphylococcal infections, including those caused by methicillin-sensitive Staphylococcus aureus (MSSA) 4
  • For methicillin-resistant Staphylococcus aureus (MRSA) skin and soft tissue infections, oral antibiotics such as linezolid, TMP-SMX, and the tetracyclines may be considered 5

Important Considerations

• The choice of antibiotic should be based on the suspected or confirmed causative organism, as well as local antibiotic resistance patterns 3, 5
• Antimicrobial stewardship programs can help optimize antibiotic use and reduce the risk of resistance 3
• The duration of therapy and the transition from intravenous to oral antibiotics should be individualized based on the patient's response to treatment 3