What is the recommended antibiotic dosage, duration, and frequency for an adult patient with lymphadenitis, with no known allergies or sensitivities?

Antibiotic Treatment for Lymphadenitis in Adults

For acute bacterial lymphadenitis in adults without known allergies, treat with flucloxacillin (or first-generation cephalosporins like cephalexin) 500 mg four times daily for 10-14 days, targeting the most common pathogens: methicillin-susceptible Staphylococcus aureus and Group A Streptococcus. 1

Uncomplicated Bacterial Lymphadenitis

First-Line Antibiotic Regimen

• Flucloxacillin 500 mg orally four times daily is the preferred narrow-spectrum beta-lactam agent for uncomplicated disease 1
• Alternative: First-generation cephalosporins (e.g., cephalexin 500 mg four times daily) are equally effective 1
• Duration: 10-14 days based on clinical response 1

Rationale for Narrow-Spectrum Therapy

• In low methicillin-resistant S. aureus (MRSA) prevalence settings, methicillin-susceptible S. aureus accounts for 49% of culture-positive cases and Group A Streptococcus for 43% 1
• MRSA represents only 6% of cases in these settings, making broad-spectrum coverage unnecessary 1
• Narrow-spectrum beta-lactam monotherapy demonstrates low rates of relapse or complications 1

Complicated Bacterial Lymphadenitis (With Abscess Formation)

Treatment Approach

• Consider clindamycin 300-450 mg orally three times daily for 14-21 days if abscess or collection is present 1
• Complicated disease requires longer antibiotic duration and higher frequency of surgical intervention 1
• Early imaging and prompt surgical drainage are recommended alongside antibiotic therapy 1

Key Clinical Indicators of Complicated Disease

• Presence of overlying skin changes (erythema, warmth, fluctuance) 2
• Multiple or bilateral nodal involvement 2
• Documented abscess or fluid collection on imaging 1
• These features significantly increase risk of treatment failure or recurrence 2

Special Considerations

Lyme Disease-Associated Lymphadenitis

If lymphadenitis occurs in the context of Lyme disease (mediastinal lymphadenitis):

• Treatment is usually unnecessary for isolated mediastinal lymphadenitis 3
• Itraconazole 200 mg three times daily for 3 days, then 200 mg once or twice daily for 6-12 weeks is recommended only if corticosteroids are administered or symptoms persist beyond 1 month 3
• Prednisone 0.5-1.0 mg/kg daily (maximum 80 mg) in tapering doses over 1-2 weeks for severe cases with compression symptoms 3

Non-Tuberculous Mycobacterial (NTM) Lymphadenitis

• Requires combination therapy with clarithromycin and rifabutin for 6-12 months if antibiotics are chosen 4
• Surgical excision is preferred over antibiotics for NTM, as antibiotic therapy alone takes months to years for resolution 4, 2
• Mycobacterium abscessus is the most common NTM species (47.8% of cases) 2

Common Pitfalls to Avoid

• Do not use amoxicillin-clavulanic acid as first-line therapy when flucloxacillin or first-generation cephalosporins are available, as this unnecessarily broadens antibiotic coverage and increases resistance risk 1
• Do not prescribe antibiotics for longer than 14 days in uncomplicated cases without documented treatment failure 1
• Do not delay surgical consultation in patients with overlying skin changes, multiple nodes, or documented abscess formation, as these require combined medical-surgical management 1, 2
• Do not assume all cervicofacial lymphadenitis is bacterial—consider NTM in children or immunocompromised adults with chronic, slowly progressive disease that fails to respond to standard antibiotics 2, 4