By: Wajidah Abdul-Khabir PGY-2 Cellulitis Updated 3/31/2017 By: Wajidah Abdul-Khabir PGY-2

Objectives To properly diagnose cellulitis To know what treatment is appropriate To know when hospitalization is needed

Pathophysiology Cellulitis is a skin infection that develops as a result of bacterial entry via breaches in the skin barrier. Manifests as erythema, edema, and warmth. Predisposing factors include disruption to the skin barrier as a result of trauma, inflammation, preexisting skin infection (ie tinea pedis), and edema. The incidence is about 200 cases per 100,000 patients per year. Breaks in the skin between the toes are perhaps the most important potential sites for pathogen entry.

Microbiology Most common pathogens are gram positive beta-hemolytic Strep and Staph aureus, including MRSA. Gram-negative aerobic bacilli are identified in a minority of cases. These include: pasteurella multocida, capnocytophaga canismorsus (dog and cat bites), pseudomonas aeruginosa (diabetics).

Diagnosis Diagnosis is based upon clinical manifestations. Cultures of blood, needle aspirations, or punch biopsies are not routinely recommended. Cultures of blood are recommended in patients with malignancy on chemotherapy, neutropenia, severe cell-mediated immunodeficiency, immersion injuries, and animal bites In mild cases, blood cultures are positive in less than 5 percent of cases. Culture results from needle aspiration vary from ≤5 to 40%, while culture of punch biopsy specimens yields a pathogen in 20-30% of cases.

Treatment Determine if purulent will need to perform incision and drainage +/- antibiotics Nonpurulent determine if infection is mild/moderate or severe

Treatment Mild: a typical infection Should receive an antimicrobial agent that is active against streptococci Moderate: typical cellulitis plus systemic signs of infection (temperature >38C, HR>90, RR> 24 or WBC<400 or>12,000) Systemic antibiotics are indicated

Treatment Severe infection: -Failed oral antibiotics OR -Immunocompromised OR -Patients with clinical signs of deeper infection such as bullae, skin sloughing, hypotension, or evidence of organ dysfunction Vancomycin plus either pipercillin- tazobactam or imipenem/meropenem is recommended as a reasonable empiric regimen for severe infections.

Treatment When should Vancomycin be utilized? penetrating trauma evidence of MRSA infection elsewhere nasal colonization with MRSA injection drug use or SIRS

Treatment Summary From: Practice Guidelines for the Diagnosis and Management of Skin and Soft Tissue Infections: 2014 Update by the Infectious Diseases Society of America

Treatment Duration of antimicrobial treatment should be at least 5 days, but treatment should be extended if the infection has not improved Elevation of the affected area and treatment of predisposing factors such as edema or tinea pedis are recommended to prevent recurrent infections

Treatment Outpatient therapy is recommended for patients who do not have SIRS, altered mental status or hemodynamic instability. Hospitalization is recommended if there is concern for a deeper or necrotizing infection, for patients with poor adherence to therapy, for infection in a severely immunocompromised patient or if outpatient treatment is failing.

MKSAP Case A 25 year old man is admitted to the hospital for chills and fever of 3 days duration. He reports that he injects heroin daily. Medical history is notable for multiple methicillin- resistant Staphlococcus aureus- associated skin and soft tissue infections and for vancomycin hypersensitivity, which causes respiratory failure and hypotension. He takes no medications.

MKSAP Case On physical examination, temperature is 39.4, blood pressure is 104/65, pulse rate is 110 and respiration rate is 20. A recent injection site in the antecubital fossa is noted, with erythema, tenderness to palpation and warmth. He has no mucosal lesions or lymphadenopathy. Cardiopulmonary examination is normal. The remainder of the examination is normal.

MKSAP Case Laboratory studies show a leukocyte count of 19,000 with 95% neutrophils. Multiple blood cultures reveal gram positive cocci in clusters. Findings on chest imaging and electrocardiography are normal.

MKSAP Case Which of the following is the most appropriate empiric antibiotic treatment for this patient? A. Ceftriaxone B. Daptomycin C. Imipenem D. Nafcillin Answer: B. Daptomycin is an effective alternative to vancomycin for the treatment of MRSA cellulitis and bacteremia in patients unable to take vancomycin.

SUMMARY Cellulitis manifests as erythema, edema, and warmth. Most common microbiological cause is gram positive beta-hemolytic Strep and Staph aureus. Treatment depends on purulent vs nonpurulent and mild vs moderate vs severe infection Hospitalization is recommended if there is concern for a deeper or necrotizing infection, for patients with poor adherence to therapy, for infection in a severely immunocompromised patient or if outpatient treatment is failing.

Sources for update: 2014 IDSA Guidelines