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cellulitis

Infection with inflammation of cellular or connective tissue. Inflammation may be diminished or absent in immunosuppressed individuals. Etiology: 1) entry of bacteria through a disruption in the skin a) laceration b) puncture wound c) fungal intertrigo d) poison oak/ivy 2) extension from contiguous focus a) abscess b) extension from ethmoid sinuses in orbital cellulitis 3) metastatic dissemination from bacteremia 4) spread through the lymphatics & blood stream 5) predisposing factors a) prior trauma b) underlying skin lesion c) peripheral neuropathy d) diabetes mellitus e) venous & lymphatic compromise 1] saphenous venectomy for CABG 2] chronic venous insufficiency - pedal edema, lower extremity edema 3] lymphedema f) arterial insufficiency g) fungal infection 1] tinea pedis 2] onychomycosis h) heart failure [5] 6) causative organisms a) group A beta-hemolytic Streptococci (> 73%) [8] (non-purulent) b) Staphylococcus aureus, including MRSA c) uncommon causes 1] group B,C,G Streptococcus, Streptococcus pneumoniae 2] immunocompromised patients a] Serratia, Proteus, Enterobacter b] Cryptococcus neoformans 3] persons handling meat, fish, poultry a] Erysipelothrix rhusiopathiae b] generally begins on hands 4] Aeromonas hydrophilia - contamination of open wound in fresh water or soil - contact with medicinal leeches [5] 5] Vibrio species a] V. vulnificus, V. alginolyticus, V. parahaemolyticus b] contamination of open wound in salt water or seafood c] cirrhosis & bullous cellulitis -> V. vulnificus 6] Pasteurella multocida - cat scratch or cat bite [5] 7] Capnocytophaga canimorsus - contact with dogs, especially patients with asplenia [5] 8] Bacillus anthracis - contact with infected animals, bioterrorism 9] Francisella tularensis a] contact or bite from infected animal (esp cats) b] tick bite [5] 10] Mycobacterium marinum - contact with fresh water or salt water, including swimming pools & fish tanks [5] 11) Mycobacterium fortuitum - footbaths, pedicures, augmentation mammoplasty, open heart surgery, razor shaving [5] Pathology: * histopathology images [20] Clinical manifestations: 1) acute onset - prolonged recovery - most patients continue to have symptoms after 10 days of therapy [36] 2) presents as well-demarcated erythematous plaque with swelling, warmth, pain, tenderness & spreading erythema 3) unilateral when it occurs in the lower leg 4) fever/chills, malaise 5) lymphadenopathy & lymphatic streaking 6) absence of pruritus 7) hemorrhagic bullous cellulitis & cirrhosis suggests Vibrio vulnificus 8) loss of sensation suggests compartment syndrome due to deep infenction 9) purulent drainage, abscesses, furuncles, carbuncles or bullous impetigo in association with cellulitis suggests Staphylococcus aureus [2] 10) edema, prurutis, central eschar suggests anthrax 11) ulcerative lesion with central eschar, localized lymphadenopathy, constituional symptoms suggest tularemia 12) trauma-associated, upper extremity papular lesion becomes ulcerative at site of innoculation, ascending lymphatic spread without systemic symptoms suggests Mycobacterium marinum 12) multiple boils suggests Mycobacterium fortuitum [5] * images [19] Diagnostic criteria: - no gold standard [36,37] - ~40% misdiagnosis [36,37] Laboratory: 1) blood cultures a) if signs & symptoms of systemic toxicity [5] b) immunodeficiency, immersion injury, mammal bite [5] b) generally unrewarding, not cost-effective [5,30] 2) skin-site cultures a) gram stain & culture from infected site [5] b) generally not useful c) skin biopsy with nucleic acid for infectious agent or culture fail to identify a pathogen in most cases [17] 3) complete blood count - neutropenia suggests ecthyma gangrenosum due to Pseudomonas Radiology: - computed tomography (CT) or magnetic resonance imaging (MRI) a) pain out of proportion to erythema b) rule out myonecrosis, necrotizing fasciitis - imaging in general not cost-effective [30] Differential diagnosis: 1) stasis dermatitis - most common misdiagnosis [31] - cellulitis can develop in the context of stasis dermatitis [5] 2) erysipelas (compare images [21]) a) superficial infection involving skin, but not soft tissue b) distinct raised border c) bright red in color 3) tissue necrosis a) necrotizing fasciitis, myonecrosis, gas gangrene b) pain/tenderness much greater than degree of erythema would suggest 4) deep vein thrombosis with stasis dermatitis 5) inflammatory carcinoma of the breast 6) cutaneous neoplasm 7) pyoderma gangrenosum 8) ecthyma gangrenosum (neutropenic patients) 9) contact dermatitis is pruritic 10) panniculitis, erythema nodosum - painful bilateral subcutaneous nodules 11) Herpes zoster [5] - cellulitis can develop in the context of Herpes zoster [5] 12) insect sting 13) drug reactions 14) eosinophilic cellulitis (the Wells syndrome) 15) gouty arthritis, gouty cellulitis - tendon involvement is common in patients with tophaceous gout - Achilles tendon (52%) - peroneal tendon (29%) 16) familial Mediterranean fever 17) foreign-body reactions [14] 18) subsutaneous abscess [36,37] * often misdiagnosed in the emergency department [28] Management: 1) general measures a) assess risk of MRSA: risk of MRSA associated with - recent hospitalization - antibiotic use - family history of cellulitis - athletic team members - prisoners b) antibiotic treatment should cover Staphylococcus unless etiology is known c) immobilization & elevation of affected limb initially may be helpful - prophylaxis for venous thromboembolism with LMW heparin if patient immobilized for >= 4 days d) moist heat my serve to localize infection e) incision & drainage of associated abscesses f) beta-lactam antibiotics are the drugs of choice [8] g) outpatient antibiotic treatment (no drainage, abscess) [6] - cephalexin (Keflex) 500 mg PO QID - addition of Bactrim to cephalexin of no benefit [10,29] - doxycycline or monocycline (MSSA, MRSA) as effective as cephalexin [38] - penicillin VK if group A Streptoccoccus most likely [5] - dicloxacillin (Dynapen) 500 mg to 1 g PO QID - if due to Staphylococcus aureus (MSSA) - erythromycin 500 mg QID (for PCN allergy) - Bactrim for community-acquired MRSA - coverage of group A Streptococci is uncertain [35] - Rocephin 1 g IM initially & for 1st few days - clindamycin (MSSA, Streptoccocus) - treatment of choice for mild, non-purulent cellulitis [5] - treatment of MRSA uncertain [35] - if systemic symptoms, MRSA coverage indicated [5,34] - linezolid (MRSA) - 5 days of therapy as effective as 10-14 days [5], 7-10 days average [38] h) inpatient antibiotic treatment (IV) - nafcillin (Nafcil, Unipen) 1-2 g IV every 4 hours - cefazolin (Ancef) 1-2 g IV every 8 hours - MRSA: vancomycin, linezolid or daptomycin - vancomycin if systemic symptoms & poor response to dicloxacillin or nafcillin [35] - duration of antibiotic therapy: - continue until 3 days after disappearance of acute inflammation - 7 days of oral antibiotics upon hospital discharge as effective as 14 days in preventing readmission in children [23] 2) special considerations a) lower extremity cellulitis associated with cutaneous ulcers in patients with diabetes mellitus - may be polymicrobial in origin - agents with anaerobic activity may be indicated - metronidazole 500 mg IV every 6 hours, 250-750 mg PO TID - clindamycin 600-900 IV every 8 hours, 150-450 mg PO QID - linezolid 600 mg IV or PO every 12 hours - penicillin 500 mg PO every 8 hours - cefoxitin 1-2 g IV every 8 hours - add Bactrim or doxycycline for MRSA coverage [7] - add fluoroquinolone to enhance gram-negative coverage b) immunocompromised patients - ticarcillin clavulanate (Timentin) 3.1 g IV every 6 hours - cefoxitin (Mefoxin) 1 g IV every 6 hours - fluoroquinolone if neutropenia [5] c) orbital cellulitis - hospitalization - broad spectrum antibiotics - surgical drainage if no improvement within 48 hours d) Erysipelothrix: penicillin e) Vibrio species - aminoglycosides - tetracycline f Aeromonas hydrophilia - aminoglycosides - chloramphenicol 3) predictors of treatment failure [16] a) temperature >38 C at triage (odds ratio, 4.3) b) chronic leg ulcers (OR, 2.5) c) chronic edema or lymphedema (OR, 2.5) - treatment of venous insufficiency, eczema, & interdigital Tinea can reduce risk of recurrent cellulitis [5] d) prior cellulitis in the same area (OR, 2.1) e) cellulitis at a wound site (OR, 1.9) 4) surgical consultation a) signs of toxicity, purple bullae, ecchymoses, sloughing of skin b) necrotizing fasciitis or myonecrosis on CT or MRI - pain out of proportion to erythema c) cellulitis following recent trauma, surgery or childbirth d) evidence of compartment syndrome 5) follow-up a) two weeks to ensure eradication of cellulitis b) tinea infection when present should be treated (including tinea pedis & onychomycosis) c) prophylactic antibiotics - recurrent cellulitis - penicillin VK 250-500 mg BID [11] includes elderly with renal insufficiency - number need to treat to prevent 1 recurrence = 5 [11] d) compression therapy (fitted compression stockings) reduces recurrence of lower leg cellulitis from 40% to 15% [33]

Related

gas gangrene (anaerobic cellulitis) perifolliculitis capitis abscedens et suffodiens; dissecting cellulitis

Specific

erysipelas Ludwig's angina; sublingual & submandibular cellulitis orbital cellulitis

General

bacterial infection skin infection sign/symptom

References

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