What antibiotics are recommended for septic prepatellar bursitis?

Antibiotic Treatment for Septic Prepatellar Bursitis

For septic prepatellar bursitis, initiate empiric anti-staphylococcal antibiotics immediately, with the specific choice depending on illness severity and local MRSA prevalence: outpatients with mild disease should receive oral TMP-SMX, doxycycline, or cephalexin, while hospitalized patients with systemic toxicity require IV vancomycin or nafcillin. 1, 2

Pathogen and Clinical Context

• Staphylococcus aureus causes 80-87.5% of all septic prepatellar bursitis cases, making anti-staphylococcal coverage the cornerstone of empiric therapy 3, 2
• Prepatellar bursitis presents more aggressively than olecranon bursitis, with higher rates of fever (71%), leukocytosis (76%), cellulitis (59%), and bacteremia (25%) 3
• Less common pathogens include Streptococcus species (particularly beta-hemolytic streptococci and S. pneumoniae) and rarely Pseudomonas aeruginosa in immunocompromised patients 3, 4

Outpatient Antibiotic Regimens (Mild Cases)

For patients who are not acutely ill and can be managed as outpatients, the following oral regimens are appropriate 1, 2:

• TMP-SMX 160-320/800-1600 mg PO every 12 hours (provides excellent MRSA coverage) 1
• Doxycycline 100 mg PO every 12 hours (covers both MSSA and community-acquired MRSA) 1
• Cephalexin 500 mg PO four times daily (for MSSA when MRSA risk is low) 5
• Clindamycin 300-400 mg PO three times daily (particularly useful for penicillin-allergic patients or when MRSA is suspected) 5

Inpatient IV Antibiotic Regimens (Severe Cases)

Hospitalize and initiate IV antibiotics for patients with systemic toxicity, extensive cellulitis, or signs of sepsis 1, 2:

For MSSA Coverage:

• Nafcillin or oxacillin 1-2 g IV every 4 hours (preferred for MSSA) 1, 5
• Cefazolin 1 g IV every 8 hours (alternative for non-immediate penicillin allergy) 1, 5

For MRSA Coverage (when local prevalence is high or beta-lactam failure):

• Vancomycin 30-60 mg/kg/day IV in 2-4 divided doses (drug of choice for MRSA) 1
• Linezolid 600 mg IV/PO every 12 hours (alternative for MRSA with good oral bioavailability) 1
• Daptomycin 4 mg/kg IV daily (for complicated MRSA skin and soft tissue infections) 1

Treatment Duration and Transition Strategy

• Total antibiotic duration should be 7-14 days for uncomplicated cases 1, 3
• The majority of patients (80%) initially require IV therapy averaging 11 days, though this can be shortened with appropriate drainage 3
• Transition to oral antibiotics when the patient is afebrile for 24-48 hours, local inflammation is improving, and oral intake is tolerated 5
• IV therapy averaged 19 days in one series using suction-irrigation, compared to 24 days without this adjunctive measure 6

Critical Adjunctive Measures

Bursal aspiration or drainage is essential and should be performed alongside antibiotic initiation 3, 6, 2:

• Aspiration alone may be sufficient for mild cases, but repeated aspirations are often necessary 2
• Percutaneous suction-irrigation with local antibiotic instillation (1% kanamycin and 0.1% polymyxin) can reduce treatment duration and prevent recurrence 6
• Surgical drainage is reserved for cases not responsive to antibiotics or recurrent infections (needed in only 5% of cases with appropriate medical management) 3, 7

Important Clinical Pitfalls

• Do not delay antibiotic administration beyond 1 hour of recognizing septic bursitis with systemic signs, as this constitutes septic shock requiring urgent treatment 1
• Avoid intrabursal corticosteroid injections in suspected septic bursitis, as this can worsen infection 2
• Obtain bursal fluid for Gram stain and culture before starting antibiotics when feasible, but do not delay treatment if aspiration would cause significant delay (>45 minutes) 1, 2
• Prepatellar septic bursitis has a 25% rate of concurrent bacteremia, so obtain blood cultures in systemically ill patients 3
• Reassess daily and consider de-escalation based on culture results and clinical response 1