Community-associated methicillin-resistant Staphylococcus aureus: prevalence in skin and soft tissue infections at emergency departments in the Greater Toronto Area and associated risk factors.
OBJECTIVE
Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA), which is caused primarily by the Canadian methicillin-resistant Staphylococcus aureus-10 (CMRSA-10) strain (also known as the USA300 strain) has emerged rapidly in the United States and is now emerging in Canada. We assessed the prevalence, risk factors, microbiological characteristics and outcomes of CA-MRSA in patients with purulent skin and soft tissue infections (SSTIs) presenting to emergency departments (EDs) in the Greater Toronto Area.


METHODS
Patients with Staphylococcus aureus SSTIs who presented to 7 EDs between Mar. 1 and Jun. 30, 2007, were eligible for inclusion in this study. Antimicrobial susceptibilities and molecular characteristics of MRSA strains were identified. Demographic, risk factor and clinical data were collected through telephone interviews.


RESULTS
MRSA was isolated from 58 (19%) of 299 eligible patients. CMRSA-10 was identified at 6 of the 7 study sites and accounted for 29 (50%) of all cases of MRSA. Telephone interviews were completed for 161 of the eligible patients. Individuals with CMRSA-10 were younger (median 34 v. 63 yr, p = 0.002), less likely to report recent antibiotic use (22% v. 67%, p = 0.046) or health care-related risk factors (33% v. 72%, p = 0.097) and more likely to report community-related risk factors (56% v. 6%, p = 0.008) than patients with other MRSA strains. CMRSA-10 SSTIs were treated with incision and drainage (1 patient), antibiotic therapy (3 patients) or both (5 patients), and all resolved. CMRSA-10 isolates were susceptible to clindamycin, tetracycline and trimethoprim-sulfamethoxazole.


CONCLUSIONS
CA-MRSA is a significant cause of SSTIs in the Greater Toronto Area, and can affect patients without known community-related risk factors. The changing epidemiology of CA-MRSA necessitates further surveillance to inform prevention strategies and empiric treatment guidelines.
Adam
Heather J
HJ
Department of Laboratory Medicine and Pathobiology, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada.
Allen
Vanessa G
VG
Currie
Andrea
A
McGeer
Allison J
AJ
Simor
Andrew E
AE
Richardson
Susan E
SE
Louie
Lisa
L
Willey
Barbara
B
Rutledge
Tim
T
Lee
Jacques
J
Goldman
Ran D
RD
Somers
Andrea
A
Ellis
Paul
P
Sarabia
Alicia
A
Rizos
John
J
Borgundvaag
Bjug
B
Katz
Kevin C
KC
D000293:Adolescent; D000328:Adult; D016009:Chi-Square Distribution; D002648:Child; D002675:Child, Preschool; D004636:Emergency Service, Hospital; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007407:Interviews as Topic; D008297:Male; D055624:Methicillin-Resistant Staphylococcus aureus / Q000302:isolation & purification*; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D009864:Ontario / Q000453:epidemiology; D015995:Prevalence; D012307:Risk Factors; D018461:Soft Tissue Infections / Q000188:drug therapy / Q000453:epidemiology* / Q000382:microbiology*; D013207:Staphylococcal Skin Infections / Q000188:drug therapy / Q000453:epidemiology* / Q000382:microbiology*