Cellulitis and Soft Tissue Infections

Cellulitis and Soft Tissue Infections Sally Williams MD Cellulitis: A very common infection 25 cases per 1000 patient years More common in men, obese patients 60% occurs in the lower extremities 74% handled as outpatients 82% of patients have just a single episode High cause of hospital readmissions Cellulitis: definition A nonspecific term that includes a large collection of skin & soft tissue infections Can include: – Erysipelas (the most common cellulitis) – Cellulitis associated with abscesses – Gangrenous cellulitis – Secondary infection of pre-existing skin lesions – Cutaneous involvement of systemic illness Normal Skin Structure Locations of Skin Infections Impetigo and ecthyma: upper epidermis Erysipelas and cellulitis: lower epidermis and dermis Carbuncles, furuncles, “boils” : deep dermis and hair follicles Necrotizing fasciitis: deep, next to muscle Microbiology of Cellulitis The vast majority are strep and staph More unusual etiologies: – Cat bite: Pasteurella – Dog bite: Capnocytophaga (splenectomized) – Rat bite: Streptobacillus – Fresh water: Aeromonas – Salt water:Vibrio and Mycobacterium marinum – Hot tubs: Pseudomonas Classic hot tub folliculitis Mix and Match Impetigo Very common skin infection in kids Has appearance of “honey colored crusts”, often on face Etiology is always staph or strep Treat with topical bactroban or oral abx Bullous impetigo is always staph, forms vesicles and bullae Impetigo quite infectious! Impetigo Erysipelas: Clinical Features Often of rapid onset Etiology is always streptococcal Often preceded by fevers, chills and groin pain (for lower extremity cellulitis) Often blisters after a few days Usually has lymphangitic streaking Almost always worsens in appearance before improving on antibiotics Classic Leg Cellulitis Facial Cellulitis Erysipelas continued Risk factors for erysipelas/strep cellulitis: – Leg edema – Previous leg surgery – Obesity – Previous breast surgery (for arm and breast cellulitis) – Tinea pedis (NOT onychomycosis) – Uncontrolled diabetes Natural History of Erysipelas Is almost always preceded by fevers, chills, and rapid increase in erythema ALWAYS gets “worse” before better – Will extend outside drawn “borders” Almost always has fever and elevated wbc Can take WEEKS to get better if has underlying edema, history of surgery etc Will often blister Is this Cellulitis?? Is this Cellulitis? Rule #1 There is no entity of “BILATERAL lower extremity cellulitis”. These are usually all chronic stasis dermatitis True cellulitis almost always has: – 1. Elevated wbc – 2. Erythema above the knee – 3. Fever, and often preceding chills – 4. Often “patches” of cellulitis on upper thigh Rule #2: Please do not culture this Wound Cultures Never culture a chronic open wound – The wounds will ALWAYS be colonized with multiple bacteria – A wound without PMNs on gram stain is probably not an infected wound – Countless unnecessary courses of antibiotics are used, predisposing pts to C difficile If you can unroof an abscess or express pus from something then culture that Rule #3: Vancomycin not needed for cellulitis without boil Classic cellulitis is streptococcal Strep releases a streptozyme to dissolve layer underneath the skin, causing rapid spread. – Multiple different strep species may cause cellulitis (A,B,C,F,G) – Strep almost always causes lymphangiitis Staph cellulitis is almost always associated with a boil or abscess Staph skin boils Cellulitis continued Treatment of non-boil, non-nec fasc cellulitis is strep targeted- Rx cefazolin or ceftriaxone As soon as they let the leg down will get bigger, redder, hotter – this is NOT treatment failure, just dependent edema. We need to prepare patients that the leg may look abnormal for months in some cases History of MRSA irrelevant if looks streptococcal – Please do NOT use vancomycin for diffuse cellulitis Cellulitis Treatment Most heavy weight people “fail” oral antibiotics due to insufficient blood levels – may need a course of iv antibiotics or high bioavailability oral antibiotic. “Failing” keflex is not a reason to use vancomycin – they just need iv cefazolin Strep itself is easy to kill but the infection causes a lot of “leftover damage” as the lymph system is often damaged. We have to prepare patients for slow improvement Summary: Leg Cellulitis Occurs most commonly in the obese or persons with a history of surgery in that leg Warn them of “worsening” when they start ambulating, leg will get redder, hotter If you use po antibiotic, need very high doses, e.g. 1-1.5g cephalexin qid If they truly “failed” high dose keflex could consider oral levoflox, has high blood levels MRSA: Not a spider bite (courtesy of GiantMicrobes.com) MRSA Epidemiology First described in 1961 Previously hospital associated, now widely community acquired since 2002 Most C.A. MRSA strains are US 300 and carry the PVL (panton valentine leukocidin) gene, causes necrosis C.A. most commonly skin/soft tissue infections, less likely bacteremia Staphylococcal Cellulitis & Boils Risk Factors Young age Immunocompromised Contact sports Crowded conditions Sharing towels, sheets etc Prior antibiotics, especially quinolones Antibiotics for Staph skin boils- do they help? Randomized studies are conflicting Many studies show no benefit to antibiotics after incision and drainage The studies that did show a benefit related a small one with using TMP-S + I&D. Drainage is likely 95% of the battle-if the pt has extensive induration oral Rx may be helpful, especially if >2 cm. Antibiotic treatment for MRSA Vancomycin for the hospitalized patient, Daptomycin also useful but expensive Clindamycin resistance up to 33% Bactrim is still sensitive >90% of the time Doxycyline resistance actually quite low Linezolid effective, but has rare drug interactions – Serotonin syndrome <.1%, still black box warning Dalbavancin/Oritavancin: likely to not be used due to >$1000 per dose of antibiotic Does antibacterial soap help? Antibacterial Soap? You Can Skip It, Use Plain Soap and Water (FDA November 2017) Most contain triclosan, a pesticide – No proven efficacy – Potential to cause antibiotic resistance – Potential to affect hormones Hand sanitizers ARE effective Recurrent skin lesions Most common in young overweight women Essentially acquisition is bad luck, can be very difficult to eradicate Nasal mupiricin for household sometimes effective, with mass washing For severe cases Bactrim suppression for a few months is an option Necrotizing Fasciitis Uncommon severe infection Etiologies may be: – Streptococcal (most common) – Polymicrobial –usually associated with gut flora (e.g. perirectal abscess, Fourniers) or trauma – Staphylococcal –usually post op, needs to be differentiated from necrotizing staph soft tissue infection which is very common. Strep necrotizing fasciitis Clinical Picture of Necrotizing Fasciitis These patients are very ill – febrile, hypotensive, tachycardic, delerious Pain out of proportion to exam Cutaneous anesthesia Very rapid spread May have skin bullae (often black), ecchymoses, usually edema Example of Leg Nec Fasc Necrotizing Fasciitis WBC almost always very high or very low Cr usually about 2, pt often in toxic shock Nec fasc is a SURGICAL EMERGENCY Antibiotics are targeted toward strep, staph or polymicrobic- Vanco + Piptazo Clindamycin is added as inhibits toxin production, but surgery is life saving How does Necrotizing fasciitis/ toxic shock happen? BAD LUCK It requires a toxin producing strain of strep (rare) often in the setting of uncontrolled DM AND a lack of immunity to the toxin (also rare) IVIG is often used with toxic shock to give patient a large “antibody load” -someone in the large pool of donors likely has an antibody to the toxin Summary: Skin Infections Cellulitis is common and is usually strep Most cellulitis gets worse before better Boils are almost always staph/MRSA and need to be drained to achieve cure Chronic stasis dermatitis is incredibly common and should not be mistaken for cellulitis Nec fasciitis is rare and pts are very ill IDSA SSTI guidelines Antibiotic humor Superbugs coming….

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