All Purulence Is Local

Epidemiology and Management of Skin and Soft Tissue Infections in Three Urban Emergency Departments

Chris Merritt; John P Haran; Jacob Mintzer; Joseph Stricker; Roland C Merchant

Disclosures

BMC Emerg Med. 2013;13(26) 

In This Article

Background

Emergency department (ED) visits in the US for skin and soft-tissue infections (SSTIs) have more than tripled in number in recent decades,[1,2] mirroring the emergence of community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA).[3,4] Two types of bacterial SSTIs predominate among ED patients: cellulitis, typically a non-purulent bacterial skin infection; and abscesses, characterized by collections of purulent fluid. Though the current epidemiology of cellulitis is understudied, the most common circulating strains of CA-MRSA have a well-described predilection for causing abscesses, and are the primary pathogens in these purulent SSTIs in many areas.[5]

Prevalence of CA-MRSA varies from region to region. Most hospitals publish antibiotic susceptibility data from their own microbiology laboratories. Commonly called "antibiograms", these documents are important tools for use by front-line clinicians in making educated treatment decisions. However, they typically report aggregate data based on bacterial isolates from all sources (blood, skin, sputum, etc.), and infrequently delineate pathogens based on the age of the patient or the source of the infection.

Although healthcare exposure appears to remain a risk factor for drug-resistant infections, ED clinicians are left with few additional demographic or clinical clues to the likelihood of resistant organisms in SSTI patients without exposures. Investigators have also noted differences in microbiology and treatment of pediatric and adult SSTIs.[6] Children beyond the neonatal period have been considered high-risk for CA-MRSA SSTIs relative to adults, though as the CA-MRSA epidemic has matured, this distinction has become less clear.[7]

Current guidelines for treatment of CA-MRSA infections do not call for routine antibiotics for adequately drained, uncomplicated abscesses.[8] Nonetheless, while incision and drainage (I&D) remains the primary treatment for abscesses, clinicians prescribe antibiotics for the majority of these patients and empiric prescription of antibiotics typically active against CA-MRSA has become routine.[9–13] In addition, many clinicians provide "double coverage", which we define as using two or more antibiotics with the intention of effectively treating MRSA, methicillin-sensitive S. aureus (MSSA) and β-hemolytic Streptococcus.[14,15]

Because antibiotics increase the cost of treatment, the incidence of adverse medication effects, and – importantly – the selective pressure leading to further antibiotic resistance, their precise role continues to be debated.[16–21] Given the inability to predict resistance based on clinical factors, some discordance between empiric treatment and pathogen is inevitable. Factors related to this discordance have not been well studied. If antibiotic choices are not well targeted, ED patients with purulent SSTIs may represent a population in whom antibiotic use could effectively be reduced, decreasing the selective pressures, cost burdens, and unintended side effects of these medications.

In this study, our primary objective was to assess – based on ED antibiotic prescribing choices and culture results – the efficiency with which ED clinicians targeted specific pathogens, particularly CA-MRSA, with empiric antibiotics. Focusing on infections that were most likely to be community-acquired rather than healthcare-associated, we assessed whether patient demographics and clinical features of presumed community-acquired SSTIs might have led emergency clinicians to prescribe empiric antibiotic therapy discordant with the susceptibility of the cultured pathogen or to institute multi-drug "double coverage". Because epidemiology and practice patterns are likely to differ in pediatric and adult patients, we examined management differences between children and adults in the ED with presumed-community-acquired SSTIs. Additionally we sought to determine the prevalent local microbiologic and practice patterns in ED patients treated for SSTIs.

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