What are the treatment options for a patient with a sore that has purple drainage, potentially indicating a bacterial infection?

Purple Drainage from a Sore: Assessment and Management

Immediate Clinical Distinction Required

If this is a skin abscess or wound with purple-appearing drainage, proceed with incision and drainage as the definitive treatment, followed by antibiotics only if systemic signs of infection are present. 1

However, if this is purple discoloration in a urinary drainage bag (not the actual wound drainage), this represents Purple Urine Bag Syndrome (PUBS), which is a benign phenomenon requiring only treatment of the underlying urinary tract infection without intensive antibiotic therapy. 2

For Skin Abscess/Wound with Purulent Drainage

Assessment of Drainage Characteristics

• Frankly purulent or turbid/cloudy drainage indicates established infection requiring immediate drainage. 3, 4
• Seropurulent discharge (turbid or cloudy fluid) represents an intermediate infection stage with bacterial invasion and requires both drainage and antibiotics. 4
• Obtain cultures from the drainage material during any drainage procedure to guide subsequent antibiotic therapy if needed. 1

Primary Treatment: Drainage

• Incision and drainage is the definitive treatment for all abscesses, involving opening the abscess, evacuating infected material, and allowing healing by secondary intention. 1
• For well-localized fluid collections, percutaneous drainage is preferable to surgical drainage. 1

Indications for Antibiotic Therapy

Add antibiotics to drainage if ANY of the following are present:

• Temperature >38.5°C or heart rate >110 beats/minute (systemic inflammatory response). 1
• Cellulitis extending >5 cm beyond the abscess margins. 1
• Immunocompromised status (diabetes, HIV, chemotherapy, chronic steroids). 1
• Incomplete source control after drainage (residual fluid collection or inadequate drainage). 1

Antibiotic Selection for Skin/Soft Tissue Infection

• Target Staphylococcus aureus (including MRSA) and streptococcal species with trimethoprim-sulfamethoxazole, doxycycline, or clindamycin. 1
• Amoxicillin alone is NOT appropriate for skin abscesses as it lacks MRSA coverage. 5

Follow-Up Assessment

• Evaluate clinical improvement within 48-72 hours, including decreased pain, swelling, and systemic symptoms. 1
• If no improvement occurs, reassess for inadequate drainage, resistant organisms, or deeper infection. 1
• Patients with ongoing infection beyond 7 days warrant diagnostic investigation and multidisciplinary re-evaluation. 1

For Purple Urine Bag Syndrome (PUBS)

Recognition and Pathophysiology

• PUBS is characterized by purple discoloration of the urinary drainage bag (not the urine itself) in patients with prolonged catheterization. 2, 6
• This occurs due to bacteria producing indigo (blue) and indirubin (red) pigments, creating purple coloration. 6
• Almost exclusively affects elderly, bedridden, catheterized patients with alkaline urine (pH ≥7.0), constipation, and high bacterial loads. 2

Causative Organisms

• Common bacteria include Providencia stuartii, Citrobacter koseri, E. coli, and Enterococcus species. 7, 8, 9
• These are indigo-producing and indirubin-producing bacteria causing urinary tract infections. 2

Management Approach

• PUBS itself is almost always asymptomatic and harmless, and intensive antibiotic treatment is NOT recommended. 2
• Treat the underlying urinary tract infection with standard antibiotics based on culture results. 7
• Purple discoloration may indicate catheter malfunction requiring immediate catheter replacement. 9
• Evaluate for catheter obstruction or malfunction if purple coloration appears, as this can be the earliest sign of drainage problems. 9

Important Caveat

• While PUBS is generally benign, some cases have progressed to severe disease states, so monitor for signs of urosepsis (fever, hypotension, altered mental status). 2