Prevalence of Antimicrobial‐Resistant Pathogens in Canadian Hospitals: Results of the Canadian Ward Surveillance Study (CANWARD 2007)
Authors: Zhanel George G , Karlowsky James A , DeCorby Mel , Nichol Kim A , Wierzbowski Aleksandra , Baudry Patricia J , Lagacé-Wiens Philippe , Walkty Andrew , Schweizer Frank , Adam Heather , McCracken Melissa , Mulvey Michael R , The Canadian Antimicrobial Resistance Alliance (CARA)  , Hoban Daryl J 
Published: May 2016

BACKGROUND: Canadian hospitals as well as hospitals worldwide
are increasingly faced with antibiotic‐resistant pathogens, including
multidrug‐resistant (MDR) strains.
OBJECTIVES: To assess the prevalence of pathogens, including the
resistance genotypes of methicillin‐resistant Staphylococcus aureus
(MRSA), vancomycin‐resistant enterococci (VRE) and extendedspectrum
beta‐lactamase (ESBL)‐producing Escherichia coli in Canadian
hospitals, as well as their antimicrobial resistance patterns.
MEtHODS: Bacterial isolates were obtained between January 1,
2007, and December 31, 2007, inclusive, from patients in 12 hospitals
across Canada as part of the Canadian Ward Surveillance Study
(CANWARD 2007). Isolates were obtained from bacteremic, urinary,
respiratory and wound specimens and underwent antimicrobial susceptibility
testing. Susceptibility testing was assessed using the Clinical
and Laboratory Standards Institute broth microdilution method.
RESULTS: In total, 7881 isolates were recovered from clinical specimens
of patients attending Canadian hospitals. The 7881 isolates were
collected from respiratory (n=2306; 29.3%), blood (n=3631; 46.1%),
wounds/tissue (n=617; 7.8%) and urinary (n=1327; 16.8%) specimens.
The 10 most common organisms isolated from 76.5% of all
clinical specimens were E coli (21.6%), methicillin‐susceptible S aureus
(13.9%), Streptococcus pneumoniae (8.9%), Pseudomonas aeruginosa
(8.0%), Klebsiella pneumoniae (5.8%), MRSA (4.9%), Haemophilus
influenzae (4.3%), coagulase‐negative staphylococci/taphylococcus
epidermidisS (4.0%), Enterococcus species (3.0%) and Enterobacter cloacae
(2.1%). MRSA made up 26.0% (385 of 1480) of all S aureus (genotypically,
79.2% of MRSA were health care‐associated MRSA and
19.5% were community‐associated MRSA), and VRE made up 1.8%
of all enterococci (62.5% of VRE had the vanA genotype). ESBLproducing
E coli occurred in 3.4% of E coli isolates. The CTX‐M type
was the predominant ESBL, with CTX‐M‐15 as the predominant
genotype. With MRSA, no resistance was observed to daptomycin,
linezolid, tigecycline and vancomycin, while resistance rates to other
agents were: clarithromycin 91.4%, clindamycin 61.8%, fluoroquinolones
88.6% to 89.6%, and trimethoprim‐sulfamethoxazole 12.2%.
With E coli, no resistance was observed to ertapenem, meropenem and
tigecycline, while resistance rates to other agents were: amikacin
0.1%, cefazolin 14.2%, cefepime 2.0%, ceftriaxone 8.9%, gentamicin
10.6%, fluoroquinolones 23.6% to 24.5%, piperacillin‐tazobactam
1.3% and trimethoprim‐sulfamethoxazole 26.6%. Resistance rates
with P aeruginosa were: amikacin 7.6%, cefepime 11.7%, gentamicin
20.8%, fluoroquinolones 23.4% to 25.1%, meropenem 8.1% and piperacillin‐
tazobactam 7.3%. A MDR phenotype (resistance to three or
more of cefepime, piperacillin‐tazobactam, meropenem, amikacin or
gentamicin, and ciprofloxacin) occurred frequently in P aeruginosa
(10.6%) but uncommonly in E coli (1.2%), K pneumoniae (1.5%),
E cloacae (0%) or H influenzae (0%).
CONCLUSIONS: E coli, S aureus (methicillin‐susceptible and MRSA),
S pneumoniae, P aeruginosa, K pneumoniae, H influenzae and Enterococcus
species are the most common isolates recovered from clinical specimens in
Canadian hospitals. The prevalence of MRSA was 26.0% (of which genotypically,
19.5% was community‐associated MRSA), while VRE and
ESBL‐producing E coli occurred in 1.8% and 3.4% of isolates, respectively.
A MDR phenotype is common with P aeruginosa in Canadian hospitals.