Prevalence of Antimicrobial-Resistant Pathogens in Canadian Hospitals: Results of the Canadian Ward Surveillance Study (CANWARD 2007)

BACKGROUND: Canadian hospitals as well as hospitals worldwideare increasingly faced with antibiotic-resistant pathogens, includingmultidrug-resistant (MDR) strains.OBJECTIVES: To assess the prevalence of pathogens, including theresistance genotypes of methicillin-resistant Staphylococcus aureus(MRSA), vancomycin-resistant enterococci (VRE) and extendedspectrumbeta-lactamase (ESBL)-producing Escherichia coli in Canadianhospitals, 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 hospitalsacross Canada as part of the Canadian Ward Surveillance Study(CANWARD 2007). Isolates were obtained from bacteremic, urinary,respiratory and wound specimens and underwent antimicrobial susceptibilitytesting. Susceptibility testing was assessed using the Clinicaland Laboratory Standards Institute broth microdilution method.RESULTS: In total, 7881 isolates were recovered from clinical specimensof patients attending Canadian hospitals. The 7881 isolates werecollected 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 allclinical 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%), Haemophilusinfluenzae (4.3%), coagulase-negative staphylococci/taphylococcusepidermidisS (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 and19.5% 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 typewas the predominant ESBL, with CTX-M-15 as the predominantgenotype. With MRSA, no resistance was observed to daptomycin,linezolid, tigecycline and vancomycin, while resistance rates to otheragents were: clarithromycin 91.4%, clindamycin 61.8%, fluoroquinolones88.6% to 89.6%, and trimethoprim-sulfamethoxazole 12.2%.With E coli, no resistance was observed to ertapenem, meropenem andtigecycline, while resistance rates to other agents were: amikacin0.1%, cefazolin 14.2%, cefepime 2.0%, ceftriaxone 8.9%, gentamicin10.6%, fluoroquinolones 23.6% to 24.5%, piperacillin-tazobactam1.3% and trimethoprim-sulfamethoxazole 26.6%. Resistance rateswith P aeruginosa were: amikacin 7.6%, cefepime 11.7%, gentamicin20.8%, fluoroquinolones 23.4% to 25.1%, meropenem 8.1% and piperacillin-tazobactam 7.3%. A MDR phenotype (resistance to three ormore of cefepime, piperacillin-tazobactam, meropenem, amikacin orgentamicin, 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 Enterococcusspecies are the most common isolates recovered from clinical specimens inCanadian hospitals. The prevalence of MRSA was 26.0% (of which genotypically,19.5% was community-associated MRSA), while VRE andESBL-producing E coli occurred in 1.8% and 3.4% of isolates, respectively.A MDR phenotype is common with P aeruginosa in Canadian hospitals