254. Antimicrobial Susceptibilities of Wound Isolates in Canada from 2007 to 2010: the CANWARD Surveillance Study
Session: Poster Abstract Session: Antimicrobial Susceptibility and Resistance
Friday, October 21, 2011
Room: Poster Hall B1
Background: Antimicrobial resistance found in pathogens causing skin and soft-tissue infections (SSTIs) is well described.  The CANWARD surveillance study assessed the pathogens causing SSTIs from 2007-2010 to determine their antimicrobial resistance patterns.

Methods: From January 2007 to November 2010, 2481 wound swab bacterial isolates were tested for antimicrobial susceptibilities using the CLSI guideline's breakpoints and broth microdilution by CANWARD, an annual Canadian surveillance study involving 14 sentinel hospitals.

Results: Wound swab isolates accounted for 7.8%, 9.3%, 13.9% and 13.2% of total isolates tested annually from 2007 through 2010, respectively.  The most common wound pathogens (n, % of isolates) were methicillin-sensitive Staphylococcus aureus (MSSA) (861, 34.7%), methicillin-resistant Staphylococcus aureus (MRSA) (282, 11.4%), Pseudomonas aeruginosa (229, 9.2%), Escherichia coli (174, 7.0%) and Streptococcus pyogenes (155, 6.2%).  The proportion of MRSA isolates of S. aureus remained stable over 4 years (mean 24.7%).  Both MSSA/MRSA isolates demonstrated 100% susceptibilities to vancomycin and linezolid.  Clindamycin and TMP/SMX susceptibilities were 92.9%/62.4% and 99.3%/94.7% for MSSA/MRSA respectively.  MRSA susceptibility to clindamycin was stable from 2007 to 2010, trending to increased susceptibility from 2007 (56.6%) to 2010 (69.7%).  The most active agents versus P. aeruginosa (% susceptible) were amikacin (98.3%), piperacillin-tazobactam (93.0%) and colistin (90.4%).  Ciprofloxacin (75.6%) and levofloxacin (68.2%) were least active.  Cephalosporin susceptibilities against E. coli ranged from cefazolin (36.8%), to ceftriaxone (93.7%) and cefepime (98.5%).  Only 7 of 174 (4.0%) E. coli isolates were extended-spectrum beta-lactamase (ESBL) producers. 

Conclusion: S. aureus is the most common pathogen isolated from wound swabs in Canada.  Oral antibiotic options remain viable for treatment of both MSSA and MRSA based on susceptibilities (TMP/SMX, linezolid).  Oral options for SSTIs caused by P. aeruginosa are more limited with fluoroquinolones having reduced susceptibilities.  Third generation and higher cephalosporins are potential therapeutic agents for E. coli SSTIs.

Subject Category: A. Antimicrobial agents and Resistance

Jared M.P. Bullard, MD FRCPC1,2, Melanie Baxter, MSc3, Heather J. Adam, PhD4, Daryl J. Hoban, PhD4 and George G. Zhanel, PhD3, (1)Cadham Provincial Laboratory, Winnipeg, MB, Canada, (2)Departments of Medical Microbiology and Paediatrics & Child Health, University of Manitoba, Winnipeg, MB, Canada, (3)University of Manitoba, Winnipeg, MB, Canada, (4)Health Sciences Centre, Winnipeg, MB, Canada


J. M. P. Bullard, None

M. Baxter, None

H. J. Adam, None

D. J. Hoban, Abbott Laboratories Ltd: Investigator, Research support
Astellas Pharma Canada Inc: Investigator, Research support
Bayer Schering Pharma AG: Investigator, Research support
Merck Frosst Canada Ltd: Investigator, Research support
Pfizer Canada Inc: Investigator, Research support
Sepracor Pharmaceuticals Inc: Investigator, Research support
The Medicines Company: Investigator, Research support

G. G. Zhanel, Pfizer Inc: Research Contractor, Research support

Findings in the abstracts are embargoed until 12:01 a.m. EST Thursday, Oct. 20 with the exception of research findings presented at IDSA press conferences.