Management of Partial Response to Flucloxacillin for Foot Cellulitis
For a 56-year-old patient with partial response to 7 days of flucloxacillin for left foot swelling, continue flucloxacillin for an additional 7-14 days to complete a total course of 14-21 days, provided the patient remains clinically well and is showing improvement. 1
Clinical Assessment Required
Before extending therapy, evaluate for:
- Presence of diabetes or other risk factors - Check for loss of protective sensation, peripheral pulses, and signs of deeper infection that would warrant imaging or specialist referral 1
- Degree of improvement - Measure reduction in erythema, warmth, and swelling compared to baseline 1
- Systemic features - Confirm patient remains afebrile with normal vital signs 1
- Underlying complications - Examine for abscess formation, lymphangitis, or involvement of deeper structures 1
Treatment Algorithm for Partial Response
Continue Current Antibiotic (Preferred Approach)
Extend flucloxacillin for another 7-14 days if the patient demonstrates:
- Reduction in swelling (even if incomplete) 1
- No fever or systemic symptoms 1
- Improving erythema and warmth 1
The rationale: Cellulitis typically requires 10-14 days total treatment, with some patients needing continuation until near-complete resolution 1. Recent evidence from the Duration of Antibiotic Therapy for Cellulitis trial showed cure rates of 67-74% with 6-12 days of flucloxacillin after initial improvement 1.
Switch Antibiotics (If Poor Response)
Change to broader spectrum coverage only if: 1
- No improvement after 3-5 days of initial therapy
- Worsening symptoms despite treatment
- Development of systemic features (fever, tachycardia)
Options include:
- High-dose amoxicillin-clavulanate (covers beta-lactamase producing organisms and gram-negatives) 1
- Cephalosporins (cefuroxime, cefpodoxime) 1
Key Considerations for Foot Infections
Diabetes-Related Concerns
If diabetes is present or suspected:
- Obtain wound cultures from tissue (not swabs) if there is any ulceration or discharge 1
- Assess vascular status - palpate pedal pulses, consider ankle-brachial index if pulses absent 1, 2
- Rule out osteomyelitis - probe-to-bone test if ulcer present; plain x-ray has low sensitivity initially but repeat in 2-3 weeks if concerns persist 1
- Ensure offloading if ulceration present 1
Duration Principles
Total antibiotic duration should be 10-14 days minimum for uncomplicated cellulitis 1. Some clinicians continue until the patient is "improved symptomatically to near normal" 1. For skin and soft tissue infections, flucloxacillin has demonstrated 88.5% cure rates with 3-12 days of treatment 3, and 92% cure rates for cellulitis with continuous infusion 4.
Common Pitfalls to Avoid
- Switching antibiotics prematurely - Partial response at 7 days is expected; complete resolution may take 14-21 days 1
- Inadequate total duration - Stopping at 7 days risks relapse even with improvement 1
- Missing deeper infection - Persistent swelling despite clinical improvement may indicate abscess, osteomyelitis, or Charcot arthropathy in diabetic patients 1
- Ignoring vascular insufficiency - Poor circulation significantly impairs healing; assess pulses and consider vascular imaging if absent 1, 2
- Relying on superficial swabs - If infection suspected, obtain deep tissue cultures after debridement 1
When to Escalate Care
Refer urgently or consider admission if: 1
- Development of systemic toxicity (fever, tachycardia, hypotension)
- Rapid progression of erythema or swelling
- Crepitus, bullae, or skin necrosis suggesting necrotizing infection
- Suspected osteomyelitis or deep abscess
- Critical limb ischemia (absent pulses, cold foot, rest pain)
Follow-Up Timing
Reassess in 3-5 days after extending therapy to confirm continued improvement 1. If no further improvement or worsening occurs, switch to broader spectrum antibiotics and investigate for complications 1.