What is the best treatment approach for a patient presenting with an axillary abscess, potentially complicated by underlying conditions such as diabetes or immunocompromised status?

Treatment of Axillary Abscess

Incision and drainage is the primary and essential treatment for axillary abscess, with antibiotics mandatory for patients with diabetes, immunocompromised status, systemic signs of infection, or extensive surrounding cellulitis. 1

Primary Treatment: Surgical Drainage

• Incision and drainage must be performed as the cornerstone of treatment for all axillary abscesses, regardless of patient immune status 1
• The incision should be made as close as possible to minimize potential fistula tract length while ensuring complete drainage of all purulent material and loculations 1
• Complete evacuation is critical because inadequate drainage is the most common cause of treatment failure and recurrence, which can reach 44% 1
• Obtain cultures from abscess material during drainage to guide subsequent antibiotic selection 1
• Packing after drainage is optional and not routinely required based on current evidence, as it adds pain and cost without proven benefit in reducing recurrence or healing time 1, 2

Antibiotic Therapy: When and What to Use

Indications for Antibiotics (Mandatory in High-Risk Patients)

Antibiotics are required for axillary abscesses when any of the following are present: 1

• Diabetes mellitus or immunocompromised status (including neutropenia, HIV, chronic steroids, chemotherapy) 1, 3
• Systemic signs of infection: temperature ≥38.5°C, pulse ≥100 bpm, or signs of sepsis 1
• Extensive surrounding cellulitis (>5 cm of erythema and induration) 1
• Multiple sites of infection or rapid progression 1
• Lack of response to incision and drainage alone 1

Empirical Antibiotic Selection

For axillary location specifically, gram-negative organisms are recovered more frequently than other body sites, requiring broader coverage: 1

Outpatient oral options (for stable patients without sepsis):

• Clindamycin 300-450 mg PO three times daily (covers MRSA, streptococci, and some gram-negatives) 1
• TMP-SMX 1-2 double-strength tablets twice daily PLUS amoxicillin 500 mg three times daily (to cover both MRSA and streptococci) 1
• Doxycycline 100 mg twice daily plus amoxicillin (alternative combination) 1

Inpatient IV options (for patients with systemic signs, diabetes, or immunocompromised):

• Vancomycin 15-20 mg/kg IV every 8-12 hours (target trough 15-20 mcg/mL for serious infections) 1
• Piperacillin-tazobactam 4 g/0.5 g IV every 6 hours for broader gram-negative and anaerobic coverage 3, 4
• For severe sepsis or septic shock: vancomycin PLUS piperacillin-tazobactam or a carbapenem (meropenem 1 g IV every 8 hours) 1, 3

Duration of Antibiotic Therapy

• 5-10 days total duration for most cases with adequate drainage 1
• Extend therapy if infection has not improved within 5 days 1
• For immunocompromised patients, continue until clinical resolution with normalization of inflammatory markers 3, 4

Special Considerations for High-Risk Patients

Diabetic Patients

• Require urgent drainage (ideally within 24 hours) due to increased risk of rapid progression 1
• Mandatory antibiotic coverage even for small abscesses 3
• Monitor blood glucose closely as infection worsens glycemic control 1

Immunocompromised Patients

• Emergent drainage is required as these patients have decreased ability to control local infection 1
• Consider broader gram-negative coverage including Pseudomonas, as ecthyma gangrenosum can occur in the axilla with neutropenia 1
• Serial assessment of WBC, CRP, and procalcitonin is mandatory 3, 4
• Evaluate for clinical improvement within 48-72 hours; if no improvement, consider imaging (ultrasound or CT) to assess for deeper collections or inadequate drainage 3, 4

Critical Pitfalls to Avoid

• Never rely on antibiotics alone without drainage in diabetic or immunocompromised patients—this leads to treatment failure 3, 4
• Do not underestimate severity in immunocompromised patients who may not mount typical inflammatory responses 1, 3
• Inadequate drainage with residual loculations is the most common cause of recurrence—ensure complete evacuation 1
• For recurrent axillary abscesses, consider hidradenitis suppurativa (especially if bilateral), which may require radical surgical excision rather than simple drainage 5
• In elderly diabetic patients with non-healing axillary abscess despite adequate drainage, obtain tissue biopsy to rule out underlying malignancy 6

Microbiology Considerations

• Staphylococcus aureus (including MRSA) accounts for approximately 65% of axillary abscesses 5, 7
• Anaerobic bacteria are present in 23% of cases, particularly in hidradenitis suppurativa 5
• Gram-negative organisms are more common in axillary location compared to other body sites 1
• Mixed flora is common, especially in diabetic and immunocompromised patients 1, 7