A 34-year-old woman with Crohn's disease on adalimumab presents with a 10-day history of multiple painful nodules on both shins. The lesions are 2-4cm in diameter, raised, tender, and erythematous without ulceration or pustulation. She reports associated joint pains in her knees and ankles but no fever. Recent colonoscopy showed active inflammation. Blood tests reveal WCC 11.2 × 10⁹/L, CRP 78 mg/L, ESR 65 mm/hr. What is the most likely diagnosis?

Cellulitis secondary to immunosuppression

Sweet's syndrome (acute febrile neutrophilic dermatosis)

Subcutaneous nodular panniculitis from adalimumab injection sites

A 72-year-old man with chronic obstructive pulmonary disease is admitted with an exacerbation and started on prednisolone 30mg daily. On day 3 of admission, he develops a painful, erythematous rash on his right shin. The affected area is warm and tender with a well-demarcated, raised border and has a characteristic orange-peel (peau d'orange) appearance. His temperature is 38.4°C. Blood tests show WCC 16.2 × 10⁹/L, CRP 128 mg/L. Which organism is most likely responsible for this infection?

Streptococcus pyogenes (Group A Streptococcus)

A hospital trust implements a new antimicrobial stewardship intervention where all prescriptions for restricted antibiotics (carbapenems, colistin, linezolid, daptomycin, tigecycline) require approval from the on-call microbiology consultant before administration. After 6 months, audit data shows a 35% reduction in use of restricted antibiotics, but there have been 8 incidents where patients experienced delayed antibiotic administration due to difficulty contacting the on-call microbiologist. What modification to this intervention would best maintain stewardship benefits while improving patient safety?

Implement a policy allowing administration of the first dose pending approval, with mandatory review within 24 hours

Allow approval by infectious diseases specialty trainees (ST4 and above) as well as consultants

Restrict the approval requirement to working hours only (9am-5pm, Monday-Friday)

Provide a 24-hour dedicated antimicrobial stewardship telephone hotline with guaranteed response within 30 minutes

Allow junior doctors to prescribe restricted antibiotics with consultant countersignature within 12 hours

A 43-year-old woman with ulcerative colitis on infliximab presents with a 3-day history of painful vesicular lesions on her right buttock and posterior thigh following a dermatomal distribution. The lesions are at various stages with some showing crusting. She is immunosuppressed but otherwise systemically well with no fever. What is the most appropriate management?

Intravenous aciclovir 10mg/kg three times daily for 7-10 days

Oral aciclovir 800mg five times daily for 7 days

Oral valaciclovir 1g three times daily for 7 days

Topical aciclovir 5% cream five times daily for 5 days

Oral famciclovir 500mg three times daily for 7 days

A hospital antimicrobial stewardship committee reviews audit data showing that 40% of patients receiving intravenous antibiotics for community-acquired pneumonia remain on IV therapy beyond 48 hours despite clinical stability and ability to take oral medications. Average length of hospital stay for pneumonia patients is 7.2 days. Which intervention is most likely to reduce this inappropriate continued use of intravenous antibiotics?

Introduce a mandatory daily checklist requiring documentation of IV-to-oral switch criteria assessment

Implement automatic stop orders for all intravenous antibiotics after 72 hours

Restrict authority to prescribe intravenous antibiotics to consultant grade doctors only

Send weekly emails to clinical teams highlighting patients eligible for oral switch

Require microbiology approval for continuation of IV antibiotics beyond 48 hours

Skin and soft tissue infections for UKMLA AKT: High-Yield Infectious Diseases Lessons

Quick Overview

Skin and soft tissue infections (SSTIs) range from superficial impetigo to life-threatening necrotizing fasciitis. NICE NG190 provides evidence-based guidance for diagnosis, severity assessment, and antibiotic selection. Rapid recognition of severity (Eron classification) and necrotizing infection is critical for appropriate management and preventing complications.

Core Facts & Concepts

NICE NG190 Classification:

Condition	Clinical Features	Depth
Impetigo	Golden crusted lesions, bullous or non-bullous	Epidermis only
Erysipelas	Well-demarcated, raised, bright red, painful	Superficial dermis + lymphatics
Cellulitis	Poorly demarcated, spreading erythema, warmth	Deep dermis + subcutaneous
Abscess	Fluctuant collection, pointing	Dermis/subcutaneous

Eron Classification (Cellulitis Severity):

Class I: No systemic toxicity, no comorbidities → oral antibiotics, outpatient
Class II: Systemically unwell OR significant comorbidity → oral/IV antibiotics, consider admission
Class III: Systemic toxicity (confusion, tachycardia, hypotension) OR limb-threatening → IV antibiotics, admission
Class IV: Sepsis/life-threatening (necrotizing fasciitis) → urgent surgical review + IV antibiotics

Figure 1: Clinical photograph showing sharply demarcated raised erythematous plaque on lower leg

Key Numbers:

📊 Bilateral leg cellulitis = consider alternative diagnosis (venous stasis, lipodermatosclerosis)
📊 LRINEC score ≥6 = 92% PPV for necrotizing fasciitis
📊 Impetigo contagious until 48h after starting antibiotics or lesions crusted

Problem-Solving Approach

Step 1: Classify the SSTI

Assess depth and extent (superficial vs deep)
Look for systemic features (fever, tachycardia, hypotension)
Identify comorbidities (diabetes, immunosuppression, PVD)

Step 2: Assess Severity (Eron Classification)

Measure vital signs, assess mental status
Mark borders with pen + date/time for progression monitoring

Step 3: First-Line Antibiotic Selection (NICE NG190)

Infection	First-Line	Duration
Impetigo (localized)	Topical fusidic acid	5 days
Impetigo (widespread)	Oral flucloxacillin	5-7 days
Cellulitis/Erysipelas	Oral flucloxacillin 500mg-1g QDS	5-7 days
Severe cellulitis (Class III-IV)	IV flucloxacillin 1-2g QDS	Until improved, then oral

Penicillin allergy: Clarithromycin or doxycycline
MRSA suspected: Add doxycycline or clindamycin

Figure 2: Clinical photograph showing dusky purple skin with bullae and skin necrosis

🚩 Red Flags for Necrotizing Fasciitis:

Severe pain disproportionate to clinical signs
Rapid progression (hours)
Dusky/purple discoloration, bullae, crepitus
Systemic toxicity (shock, organ failure)
Hypoaesthesia (nerve involvement)

Step 4: When to Suspect MRSA

Recent hospitalization/nursing home resident
IV drug use
Known MRSA colonization/previous infection
Recurrent SSTIs despite appropriate antibiotics

Analysis Framework

Cellulitis vs DVT vs Venous Insufficiency:

Feature	Cellulitis	DVT	Venous Insufficiency
Onset	Acute (days)	Acute/subacute	Chronic
Distribution	Unilateral	Unilateral	Often bilateral
Erythema	Present, spreading	Absent	Hemosiderin staining
Warmth	Marked	Mild	Absent
Fever	Common	Rare	Absent
D-dimer	Variable	Elevated	Normal

LRINEC Score Components (for necrotizing fasciitis):

CRP >150mg/L (4 points)
WCC >25 (2 points), 15-25 (1 point)
Haemoglobin <110g/L (2 points), 110-135 (1 point)
Sodium <135mmol/L (2 points)
Creatinine >141μmol/L (2 points)
Glucose >10mmol/L (1 point)

⚠️ Warning: LRINEC score has limited sensitivity (68%) - clinical suspicion overrides negative score

Visual Aid

MRSA Coverage Indications:

Scenario	Action
Healthcare-associated risk factors	Add doxycycline/clindamycin
Culture-confirmed MRSA	Switch to appropriate agent
Recurrent infections	Consider decolonization (nasal mupirocin + chlorhexidine washes)

Key Points Summary

✓ Eron Classification determines management: Class I outpatient oral, Class III-IV admission + IV antibiotics

✓ First-line cellulitis: Flucloxacillin 500mg-1g QDS for 5-7 days; clarithromycin if penicillin-allergic

✓ Necrotizing fasciitis red flags: Pain >> signs, rapid progression, dusky skin, crepitus, systemic toxicity → emergency surgical debridement

✓ Bilateral leg cellulitis is rare - consider venous insufficiency, lipodermatosclerosis, or systemic causes

✓ MRSA coverage indicated for healthcare-associated risk, IV drug use, or recurrent infections despite treatment

✓ Mark cellulitis borders with pen + time to monitor progression objectively

✓ LRINEC score ≥6 suggests necrotizing infection but clinical suspicion overrides negative score (68% sensitivity)

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