Objectives: This study aimed to estimate the city-wide prevalence of methicillin-resistant Staphylococcus aureus (MRSA) in patients (≥18 years old) presenting with skin and soft tissue infections (SSTIs) to the emergency departments (EDs) of a Canadian Academic Health Care Center. Secondary objectives were to identify demographic and clinical variables associated with MRSA, and determine MRSA antimicrobial susceptibilities and genotypes.
Methods: This prospective observational study was conducted over 2 months. Participants completed a Health and Lifestyle Questionnaire. Cultures of the infection site, nares, and throat were obtained and MRSA isolates were confirmed by polymerase chain reaction. Patient characteristics were summarized using descriptive statistics and MRSA prevalence and 95% confidence intervals were estimated using standard equations. Backwards stepwise multivariate logistic regression models determined predictor variables independently associated with MRSA colonization or infection.
Results: Of 205 patients, 35 (17.1%) were infected or colonized with MRSA. Seventy-eight (38.0%) of the infection site cultures grew S. aureus of which 27 (34.6%) were MRSA. Incarceration, known exposure to MRSA and involvement in competitive sports were significant predictors of MRSA SSTIs. Antimicrobial susceptibility among MRSA isolates was trimethoprim/sulfamethoxazole, vancomycin, gentamicin, and linezolid 100%, clindamycin 75%, ciprofloxacin 59.3%, and erythromycin 7.4%. Sixty-nine percent of MRSA cases fit the clinical definition of community associated; subsequently 77% were confirmed as CMRSA 10, a recognized community-acquired MRSA.
Conclusion: Community-acquired -MRSA is a significant pathogen of SSTIs in EDs of a Canadian teaching center. MRSA should be considered when initiating empiric antibiotic therapy, particularly in patients with risk factors.