What is the primary concern in a case of cellulitis that fails to resolve with antibiotics and is characterized by spikes of fever, abscess (A) or resistant organisms (B)?

Abscess Formation is the Primary Concern

When cellulitis fails to respond to appropriate antibiotics and is accompanied by fever spikes, the most likely explanation is an underlying abscess that requires drainage, not simply resistant organisms. 1

Why Abscess Takes Priority

• Antibiotics alone cannot penetrate and resolve a walled-off collection of pus, making incision and drainage the primary treatment for abscesses, with antibiotics playing only an adjunctive role 1

• The clinical scenario described—persistent infection despite antibiotics plus fever spikes—is the classic presentation of a collection requiring source control rather than just antimicrobial therapy 1

• For simple abscesses, incision and drainage is the definitive treatment, and antibiotics are not even needed unless there is significant surrounding cellulitis, systemic signs of infection, or immunocompromise 1

The Role of Resistant Organisms

• While resistant organisms (particularly MRSA) are important considerations in skin infections, MRSA is actually an unusual cause of typical cellulitis and routine coverage is unnecessary 2

• Even when MRSA is present, the fundamental problem in treatment failure with fever spikes is more likely inadequate source control (undrained abscess) rather than the organism's resistance pattern 1

• Studies show that adding MRSA coverage (trimethoprim-sulfamethoxazole) to standard cellulitis treatment does not improve outcomes in uncomplicated cases without abscess 3

Clinical Algorithm for This Scenario

When cellulitis doesn't resolve on antibiotics:

1. First, actively search for an abscess using physical examination and point-of-care ultrasound if available 4

   • Look for fluctuance, localized collection, or deeper extension
   • Fever spikes strongly suggest a drainable collection 1

2. If abscess is found, perform incision and drainage immediately 1, 4

   • This is the definitive treatment
   • Consider antibiotics only if there is extensive surrounding cellulitis, systemic signs, or immunocompromise 1

3. Only after ruling out abscess should you consider resistant organisms 5

   • Obtain cultures if not already done
   • Consider MRSA coverage if specific risk factors present: penetrating trauma, purulent drainage, known MRSA colonization, IV drug use 2
   • Consider other resistant or unusual organisms (though rare) 6

Critical Pitfall to Avoid

• Do not simply escalate antibiotics or add MRSA coverage without first ensuring adequate source control 1, 5
• An undrained abscess will continue to expand and cause systemic infection regardless of antibiotic choice 1
• Failure to drain an abscess can lead to progression into deeper tissue planes and life-threatening complications 1