Prevalence of MRSA in Skin and Soft Tissue Infections in Two Ontario Emergency Departments.

Objective & Hypothesis: The objective of this prospective study is to determine the prevalence of MRSA and community acquired MRSA (CA-MRSA) in adult patients (>17yrs old) presenting with skin or soft tissue infections to the emergency departments (EDs) of an academic health care setting in London, Ontario. Secondary objectives will include the identification of demographic and clinical variables associated with MRSA, characterization of MRSA antimicrobial susceptibilities and genotypes, and determining the effects of treatment on MRSA colonization. We believe that the prevalence of MRSA and CA-MRSA in London, Ontario will be lower than rates recently published by academic hospitals from the United States. The hypothesis of the study is that patients presenting to the Emergency Departments in London, Ontario with skin and soft tissue infections will have a 10% prevalence of CA-MRSA, but certainly the prevalence may be much higher.

Purpose: Results from this research may be used as part of the guidelines for empirical S aureus treatment in the region, thus reducing possible morbidity and mortality from delayed or suboptimal treatment of CA-MRSA infections. This information, along with an improved understanding of risk factors associated with MRSA infection in a Canadian setting, has the potential to change the practice of physicians who are considering empiric antibiotic therapy for skin and soft tissue infections.

This study will focus on the epidemiology of patients with skin or soft tissue infections presenting to the adult emergency departments (EDs) at the London Health Sciences Centre (LHSC) and the Urgent Care Center at St. Joseph's Health Centre (SJHC). By using a comparison group of non CA-MRSA infections, the proportion of CA-MRSA with relation to the total MRSA and methicillin sensitive Staphylococcus aureus (MSSA) in the region will be investigated. The study will also investigate the risk factors in the CA-MRSA population including: demographics, housing history, contact with the health care system, past CA-MRSA infection, asymptomatic CA-MRSA colonization, colonization/infection of close contacts, involvement in contact sports/team sports, hygienic body shaving, chronic skin disorders, recurrent/recent antibiotic use, IV drug use, contact with incarcerated individuals, and chronic disease.

Through follow-up visits at one and three months involving nares and throat swabs of patients initially testing positive for MRSA the effects of treatment on MRSA colonization will be determined. Furthermore, a follow-up questionnaire will be administered to all patients at one month to determine complication rates for patients colonized with MRSA versus those not colonized.

The current recommendations for antibiotic treatment of unknown S. aureus infection are based on clinical judgment, and therefore an understanding of regional incidence and susceptibility of CA-MRSA are essential for empiric treatment. Through the microbiological analysis of the cases, laboratory parameters and antibiotic susceptibility of CA-MRSA presenting to LHSC will be established. As well, the clinical characteristics of these patients will be documented to aid clinicians in recognizing patients presenting with CA-MRSA.