Overview
Definition:
Cellulitis is a common bacterial infection of the dermis and subcutaneous tissues, characterized by localized erythema, warmth, swelling, and pain
In pediatric patients, it can range from superficial to deep, with potential for serious complications
Methicillin-resistant Staphylococcus aureus (MRSA) has become a significant pathogen, necessitating specific treatment considerations, particularly in inpatient settings.
Epidemiology:
Cellulitis is a frequent reason for pediatric hospital admission
While many cases are caused by Streptococcus pyogenes and methicillin-susceptible Staphylococcus aureus (MSSA), community-acquired MRSA (CA-MRSA) accounts for a substantial proportion of infections, particularly in areas with high prevalence
Risk factors include skin breaks, insect bites, eczema, and previous cellulitis episodes.
Clinical Significance:
Prompt and appropriate management of pediatric cellulitis is crucial to prevent complications such as abscess formation, bacteremia, sepsis, and osteomyelitis
Understanding MRSA coverage and the safe transition from intravenous to oral antibiotics is vital for effective inpatient care, optimizing patient outcomes, reducing length of hospital stay, and curbing antibiotic resistance.
Clinical Presentation
Symptoms:
Fever
Chills
Localized warmth, redness, and swelling of the affected skin
Pain or tenderness at the site
In severe cases, blistering, bullae, or purpura may be present
Regional lymphadenopathy may occur
Malaise and irritability are common in young children.
Signs:
Erythematous, warm, swollen, and tender plaque with ill-defined borders
Crepitus is rare but may suggest gas-forming organisms
Petechiae or ecchymoses may indicate severe infection
Vital sign abnormalities may include fever and tachycardia.
Diagnostic Criteria:
Diagnosis is primarily clinical, based on characteristic physical examination findings of localized inflammation
Laboratory investigations are supportive and may be indicated in severe cases or when complications are suspected
There are no strict diagnostic criteria
a high index of suspicion in the context of suggestive symptoms and signs is paramount.
Diagnostic Approach
History Taking:
Onset and duration of symptoms
Presence of fever, chills, and systemic symptoms
History of trauma, insect bites, or skin lesions
Pre-existing skin conditions such as eczema or psoriasis
Recent antibiotic exposure
Travel history and community prevalence of MRSA
Immunocompromise or underlying medical conditions.
Physical Examination:
Assess the extent and characteristics of the skin lesion (erythema, warmth, edema, tenderness, induration, presence of bullae, pustules, or purulent drainage)
Examine for satellite lesions
Evaluate for regional lymphadenopathy
Assess for signs of systemic involvement (e.g., vital signs, mental status)
Inspect for entry points of infection such as abrasions or insect bites.
Investigations:
Blood cultures: Indicated in febrile patients, those with signs of sepsis, or severe local infection to identify bacteremia
Complete blood count (CBC) with differential: May show leukocytosis with a left shift
C-reactive protein (CRP): Elevated in infection
Wound culture: If purulent drainage is present or an abscess is suspected, to identify the causative organism and guide antibiotic therapy, including sensitivities
Imaging: Ultrasound may help differentiate cellulitis from abscess
Plain radiographs are useful to rule out underlying osteomyelitis if joint involvement is suspected or there is a history of penetrating trauma near a bone.
Differential Diagnosis:
Abscess: Characterized by fluctuance and purulent material
Deep vein thrombosis (DVT): Usually presents with swelling, pain, and warmth but lacks the characteristic skin erythema of cellulitis
Allergic contact dermatitis: Often presents with pruritus and eczematous changes
Erythema migrans (Lyme disease): Typically an expanding erythematous rash with central clearing
Cellulitis mimicking fungal infections: Can occur in immunocompromised individuals
Necrotizing fasciitis: A severe, rapidly progressing infection characterized by intense pain out of proportion to physical findings, crepitus, and systemic toxicity.
Management
Initial Management:
Intravenous (IV) fluid resuscitation if signs of dehydration or sepsis are present
Prompt initiation of empiric antibiotic therapy
Elevation of the affected limb to reduce edema
Pain management with analgesics.
Medical Management:
Empiric antibiotic therapy should cover both streptococci and S
aureus, including MRSA, especially in moderate to severe cases or in regions with high MRSA prevalence
For inpatient management of suspected MRSA cellulitis: Vancomycin (IV): Typical dose 15 mg/kg every 8-12 hours, adjust based on renal function and trough levels (target trough 10-20 mcg/mL)
Clindamycin (IV): 10-13 mg/kg/dose every 6-8 hours (max 600 mg/dose), particularly effective for toxin-producing strains
Linezolid (IV/PO): 10-15 mg/kg/dose every 8-12 hours (max 600 mg/dose)
Daptomycin (IV): 4 mg/kg/day once daily
For suspected MSSA or Streptococcus: Cefazolin (IV): 100-150 mg/kg/day divided every 8 hours
Nafcillin or Oxacillin (IV): 100-150 mg/kg/day divided every 6 hours.
Transition To Oral Therapy:
Transition to oral antibiotics is typically considered when the patient is clinically improving: Fever has resolved for at least 24-48 hours
Localized signs of inflammation (erythema, swelling, tenderness) are significantly improving
Patient is hemodynamically stable and able to tolerate oral intake
Oral agents should provide coverage against the identified pathogen or suspected pathogens
Common oral agents include: Clindamycin (300-450 mg PO TID for adults
7-13 mg/kg/day divided TID/QID for children)
Trimethoprim-sulfamethoxazole (TMP-SMX) (e.g., 160/800 mg PO BID for adults
8-10 mg/kg/day of TMP component divided BID for children - avoid if G6PD deficiency)
Linezolid (600 mg PO BID for adults
10-15 mg/kg/dose BID for children)
Duration of therapy is typically 7-14 days, individualized based on response and severity.
Surgical Management:
Surgical intervention is indicated for fluctuant abscesses requiring drainage
Incision and drainage (I&D) should be performed
Necrotizing fasciitis requires urgent surgical debridement
Other indications include failure to improve with antibiotics and suspicion of deep tissue involvement or osteomyelitis.
Supportive Care:
Regular monitoring of vital signs, pain level, and clinical signs of infection
Appropriate wound care if drainage is present
Patient and family education regarding antibiotic adherence, wound care, and recognition of worsening symptoms
Ensure adequate hydration and nutrition.
Complications
Early Complications:
Bacteremia
Sepsis
Septic shock
Abscess formation
Lymphangitis
Phlebitis
Necrotizing fasciitis
Deep vein thrombosis
Compartment syndrome.
Late Complications:
Osteomyelitis (if adjacent to bone)
Chronic lymphedema
Recurrent cellulitis
Skin changes (hyperpigmentation, scaling)
Chronic pain.
Prevention Strategies:
Prompt treatment of skin breaks and wounds
Good skin hygiene
Management of underlying skin conditions like eczema
Prompt treatment of any suspected infection
Patient education on early recognition of symptoms and seeking medical attention.
Prognosis
Factors Affecting Prognosis:
Promptness and appropriateness of antibiotic therapy
Virulence of the causative organism
Presence of comorbidities or immunocompromise
Development of complications such as sepsis or osteomyelitis.
Outcomes:
With appropriate treatment, most pediatric patients with cellulitis achieve a full recovery
Those with MRSA or severe infections may require longer treatment courses and closer monitoring
Complications can significantly impact long-term outcomes.
Follow Up:
Close follow-up is recommended to ensure resolution of infection and to monitor for recurrence
For patients with recurrent cellulitis, prophylaxis with oral antibiotics (e.g., TMP-SMX or cephalexin) may be considered for several months
Education on preventive measures is key for long-term management.
Key Points
Exam Focus:
MRSA is a common cause of pediatric cellulitis
empiric coverage is crucial in moderate to severe cases
Transition to oral antibiotics requires clinical improvement: afebrile, improving local signs, stable
Oral TMP-SMX, clindamycin, and linezolid are key agents for MRSA coverage
Differentiate cellulitis from abscess based on fluctuance.
Clinical Pearls:
Always consider MRSA, especially with purulent drainage or if the patient has risk factors
Do not discharge a febrile patient with cellulitis
Assess for underlying skin conditions that predispose to cellulitis
Educate families on recognizing signs of worsening infection
Ensure appropriate dosing for pediatric patients, especially with clindamycin and TMP-SMX.
Common Mistakes:
Underestimating the prevalence of MRSA, leading to delayed or inadequate MRSA-directed therapy
Discharging patients too early, before clinical improvement is evident and they are safe for oral antibiotics
Inadequate pain control
Failing to consider deeper infections like osteomyelitis or necrotizing fasciitis.