Molecular characterization of predominant Streptococcus pneumoniae serotypes causing invasive infections in Canada:the SAVE study, 2011-15

Objectives: This study characterized the 11 most predominant serotypes of invasive Streptococcus pneumoniae infections collected by the annual SAVE study in Canada, between 2011 and 2015. Methods: A subset of the 11 most predominant serotypes (7F, 19A, 22F, 3, 12F, 11A, 9N, 8, 33F, 15A and 6C) collected by the SAVE study was analysed using PFGE and MLST, as well as PCR to identify pilus-encoding genes. WGS analyses were performed on a subset of the above isolates plus a random selection of background strains. Results: Of the predominant serotypes analysed, 7F, 33F and 19A were obtained more commonly from children 65 years of age. Pneumococcal pilus PI-1 was identified in antimicrobial-susceptible serotype 15A (61/212) and <10% of 6C isolates (16/188). PI-2 was found in serotype 7F (683/701) and two-thirds of 11A isolates (162/241). Only serotype 19A-ST320 possessed both pili. Molecular and phylogenetic analyses identified serotypes 19A, 15A, 6C, 9N and 33F as highly diverse, whereas 7F, 22F and 11A demonstrated clonality. Antimicrobial resistance determinants were common within diverse serotypes, and usually similar within a clonal complex. Conclusions: Despite successful use of conjugate vaccines, S. pneumoniae remains a highly diverse organism in Canada. Several predominant serotypes, both antimicrobial susceptible and MDR, have demonstrated rapid clonal expansion or an increase in diversity. As S. pneumoniae continues to evolve in Canada, WGS will be a necessary component in the ongoing surveillance of antimicrobial-resistant and expanding clones

Antimicrobial susceptibility testing of invasive isolates of Streptococcus pneumoniae from Canadian patients:the SAVE study, 2011-15

Objectives: To assess antimicrobial susceptibility for 14 agents tested against 6001 invasive isolates of Streptococcus pneumoniae cultured from invasive patient samples from 2011 to 2015 as a part of the annual SAVE study. Methods: Isolates of S. pneumoniae were tested using the standard CLSI broth microdilution method (M07-A10, 2015) with MICs interpreted by CLSI M100 27th Edition (2017) MIC breakpoints. Results: From 2011 to 2015, small but significant increases (P ≤ 0.05) in the percentage susceptibility for penicillin (interpreted by all three CLSI MIC breakpoint criteria) (increase of 1.7%-3.2%), clindamycin (3.1%) and ceftriaxone (interpreted by non-meningitis and meningitis CLSI MIC breakpoint criteria) (1.1%-1.5%) were observed. Susceptibility rates for clarithromycin and other commonly tested antimicrobial agents remained unchanged (P > 0.05) over the 5 year period. Isolates with an MDR phenotype (resistance to three or more antimicrobial agent classes) decreased significantly (P  0.05) with patient gender (exception: clarithromycin) but were associated (P ≤ 0.05) with patient age (chloramphenicol and clindamycin) or specimen source (penicillin, doxycycline, trimethoprim/sulfamethoxazole and clindamycin), as well as geographic location in Canada and concurrent resistance to penicillin or clarithromycin. Conclusions: The in vitro susceptibility of invasive isolates of S. pneumoniae in Canada to penicillin, clindamycin and ceftriaxone increased from 2011 to 2015, coincident with a significant decrease in MDR phenotypes

Analysis of 1560 inpatient and outpatient Escherichia coli isolates from across Canada - Results from the CANWARD 2007 study CANWARD 2007

OBJeCtIveS: Escherichia coli was the most common pathogen isolated in the Canadian Ward Surveillance Study (CANWARD 2007) and remains one of the most common pathogens isolated in all health care settings. An in-depth analysis of all E coli isolates was performed to determine the distribution and demographics associated with resistance to antimicrobials, presence of extended-spectrum beta-lactamases (ESBLs) and multidrug resistance (MDR; concurrent resistance to agents from three or more different antimicrobial classes). MethODS: The CANWARD 2007 study characterized pathogens isolated from inpatient (surgical and medical wards, and intensive care units) and outpatient (emergency departments and clinics) areas of 12 Canadian hospitals between January and December 2007. E coli susceptibility to 12 antimicrobials was determined, ESBL production was determined, and a multivariate nominal logistic regression model was designed to determine if sex, isolation from a sterile site, inpatient versus outpatient status, and age were significantly associated with susceptibility to the tested antimicrobials, MDR or ESBL production. ReSuLtS: In total, 1702 E coli isolates, representing 21.6% of all isolates collected in the CANWARD 2007 study, were investigated. Of these, 1560 isolates fell within the primary objective of the study and were included in the present analysis. Susceptibilities were greater than 90% for meropenem (100%), ertapenem (100%), tigecycline (99.9%), piperacillin-tazobactam (97.9%), cefepime (97.9%), ceftriaxone (95.4%), nitrofurantoin (95.2%), cefoxitin (94.8%), amoxicillinclavulanate (92.9%) and gentamicin (91.4%). Cefazolin (89.4%), the fluoroquinolones (ciprofloxacin, 79.4%; levofloxacin, 79.9%) and trimethoprim-sulfamethoxazole (75.7%) were less active agents. In the multivariate model, invasive isolates were significantly associated with lower susceptibility rates for trimethoprim-sulfamethoxazole. Increasing age was associated with lower susceptibility to fluoroquinolones, ceftriaxone, cefepime, gentamicin and nitrofurantoin, as well as ESBL production. Sex was not associated with resistance to any antimicrobial or to ESBL production. Inpatient status was associated with higher resistance rates to amoxicillin-clavulanate, cefazolin, fluoroquinolones and trimethoprim-sulfamethoxazole. Isolation of an ESBL producer was only found to be independently associated with age, being more common in older patients. MDR was not found to be associated with any variable measured when ESBL producers were excluded from analysis. CONCLuSIONS: E coli antimicrobial susceptibility varies according to patient factors. Age and inpatient status were the most important determinants in the present analysis and should be considered when prescribing empirical antimicrobial therapy. Fluoroquinolones and sulfonamides should be used cautiously and in consideration of local resistance patterns for infections caused by E coli, due to lower susceptibility rates. Independent factors associated with antimicrobial resistance were age, inpatient status and isolation from a sterile site. These factors should be considered when empirically treating infections likely caused by E coli. Local antimicrobial prescribing practices, in particular the liberal use of fluoroquinolones, and inadequate infection control practices may be reducing susceptibility rates. OBJeCtIFS : L&apos;Escherichia coli était le pathogène le plus isolé dans l&apos;étude CANWARD 2007 sur la surveillance des services aux hospitalisés canadiens et demeure l&apos;un des pathogènes les plus isolés en milieu de santé. On a effectué une analyse approfondie de tous les isolats d&apos;E coli pour déterminer la répartition et la démographie associées à la résistance aux antimicrobiens ainsi qu&apos;à la présence de bêta-lactamases à large spectre (ESBL) et de multirésistance (résistance conjointe à au moins trois classes d&apos;antimicrobiens). MÉthODOLOGIe : L&apos;étude CANWARD 2007 caractérisait les pathogènes isolés de patients hospitalisés (service de chirurgie, service médical et unité de soins intensifs) et ambulatoires (urgence et cliniques) de 12 hôpitaux canadiens entre janvier et décembre 2007. On a déterminé la susceptibilité de l&apos;E coli à 12 antimicrobiens ainsi que la production d&apos;ESBL et conçu un modèle de régression logistique nominale multivariée pour déterminer si le sexe, l&apos;isolement d&apos;un foyer stérile, le statut de patient hospitalisé ou ambulatoire et l&apos;âge s&apos;associaient de manière significative à la susceptibilité aux antimicrobiens vérifiés, à la multirésistance ou à la production d&apos;ESBL. RÉSuLtAtS : Au total, on a évalué 1 072 isolats d&apos;E coli, représentant 21,6 % de tous les isolats prélevés dans le cadre de l&apos;étude CANWARD 2007. De ce nombre, 1 560 isolats respectaient l&apos;objectif primaire de l&apos;étude et ont été inclus dans la présente analyse. Les susceptibilités étaient supérieures à 90 % pour le méropénem (100 %), l&apos;ertapénem (100 %), la tigécycline (99,9 %), la pipéracilline-tazobactam (97,9 %), la céfépime (97.9 %), la ceftriaxone (95,4 %), la nitrofurantoïne (95,2 %), la céfoxitine (94,8 %), l&apos;amoxicilline-clavulanate (92,9 %) et la gentamicine (91,4 %). La céfazoline (89,4 %), les fluoroquinolones (ciprofloxacine, 79,4 %, lévofloxacine, 79,9 %) et le triméthoprim-sulfaméthoxazole (75,7 %) étaient moins actifs. Dans le modèle multivarié, les isolats envahissants étaient associés de manière marquée à des taux de susceptibilité plus faibles pour le triméthoprim-sulfaméthoxazole. Le vieillissement s&apos;associait à une susceptibilité plus faible aux fluoroquinolones, à la ceftriaxone, à la suite page suivante Lagacé-Wiens et al Can J Infect Dis Med Microbiol Vol 20 Suppl A Spring 2009 50A E scherichia coli is the most commonly isolated clinically relevant Gram-negative organism in most health care settings (1-3). Although most commonly associated with urinary tract infections, all body sites can be involved. Furthermore, resistance to multiple antimicrobials is increasing and multidrug resistant (MDR; concurrent resistance to agents from three or more different antimicrobial classes) isolates are common (1,4,5). Appropriate empirical antimicrobial choice must take into account local resistance patterns and other demographic variables such as patient age, site and severity of infection, sex, inpatient status as well as previous antimicrobial use, stay in hospitals or personal care homes, and colonization with antimicrobial resistant organisms (1,6). The purpose of the present study was to provide an in-depth analysis of patient factors associated with drug resistance in the most commonly isolated organism overall in Canadian hospitals. MethODS E coli isolates were obtained as part of the Canadian Ward Surveillance Study (CANWARD 2007), which collected isolates submitted to 12 clinical microbiology laboratories from tertiary care hospitals in seven provinces across Canada. Submitting sites and collection strategy are described elsewhere in the present supplement (2). Isolates had to be deemed clinically significant by the referring laboratory&apos;s current specimen work-up protocol. Demographic information collected with each isolate included patient age, sex, site of infection and the location of patient contact (surgical or medical ward, emergency room, intensive care unit [ICU] or hospital clinic). A minimum number of isolates from each hospital location and anatomical site was requested to provide more power to the study. The implication of this collection strategy is that the anatomical distribution of pathogen isolation and inpatient versus outpatient distribution does not reflect the true distribution in the population studied. Isolates were collected within both primary and secondary study objectives and only isolates collected within the primary objective were considered in this analysis. For statistical analysis, age was divided into four categories: 20 years and younger, 21 to 60 years, 61 to 80 years, and 81 years and older, and location of patient contact was divided into either inpatient (wards and ICUs) or outpatient (emergency room and clinics). Information on previous antimicrobial exposure, hospitalization duration and underlying medical conditions was not available. Antimicrobial susceptibility to amoxicillin-clavulanate, cefazolin, cefepime, ceftriaxone, ciprofloxacin, gentamicin, nitrofurantoin, levofloxacin, meropenem, ertapenem, piperacillin-tazobactam, tigecycline and trimethoprim-sulfamethoxazole was determined using broth dilution as described elsewhere in the present supplement (2). Screening for ESBL production was achieved using a 1 µg/mL or greater ceftriaxone breakpoint and confirmation was with the Clinical and Laboratory Standards Institute-recommended disk diffusion method (7). Univariate analysis using the c 2 (or Fisher&apos;s exact test where required) was undertaken to identify relationships between susceptibility to each of the antimicrobials and ESBL production; and the following variables: sex, age group, inpatient/outpatient status and isolation from a sterile site (blood, cerebrospinal fluid, synovial fluid). Relationships where the P&lt;0.20 in the univariate analysis were included in a multivariate nominal logistic regression model to determine independent explanatory variables. Initially, a full factorial multiple logistic regression analysis was performed using the potential explanatory variables identified in the univariate analysis for each antimicrobial, and then a backward selection so that all factors remaining in the model were statistically significant at a 5% level (P&lt;0.05). Statistical analysis was undertaken using JMP software version 7.0 (SAS Institute Inc, USA). ReSuLtS Of 7881 total organisms, 1702 E coli (21.6%) were collected from the CANWARD 2007 study, making it the most common organism isolated from patients in Canadian hospitals overall. Of these, 1560 fell within the primary objective and the remaining 142 were submitted as putative ESBL producers for separate analysis and excluded from the present analysis. The mean age of patients infected with E coli was 56.9 years; 12.3% of E coli isolates were from patients younger than 21 years, 34.7% were 21 to 60 years of age, 33.9% were 61 to 80 years of age and 19.1% were older than 80 years of age. There were more samples from women (59.3%); with both sexes combined, 50.5% were invasive isolates (all bloodstream), and 40.7% were from urine, 6.4% from respiratory sources and 2.4% from wounds. Note that the sampling strategy was biased to include a surplus of bloodstream isolates to have greater numbers of these for analysis and this does not represent the true source distribution of E coli infections. The distribution among provinces was British Columbia, 9.7%; Alberta, 7.6%; Saskatchewan, 9.1%; Manitoba, 9.2%; Ontario, 28.3%; Quebec, 29.2% and Nova Scotia, 6.9%. Isolates were not obtained from Newfoundland, Nunavut, the Northwest Territories, Yukon, New Brunswick or Prince Edward Island. Minimum inhibitory concentrations (MICs) required to inhibit 50% and 90% of organisms (MIC 50 , MIC 90 ) and percentage of isolates susceptible to the antimicrobials are provided in Resistance in E coli from Canadian inpatients and outpatients Can J Infect Dis Med Microbiol DISCuSSION Low susceptibility of ICU E coli isolates to fluoroquinolones and trimethoprim-sulfamethoxazole was not unexpected given the wide use of these antimicrobials in both inpatients and outpatients. In particular, the dramatic increase in fluoroquinolone resistance has been observed in many settings (8-10). Our observations suggest that first-generation cephalosporins and amoxicillin-clavulanate are still useful agents for infections caused by E coli in that susceptibility rates remain near 90% overall. This is particularly true of outpatient isolates where susceptibility is greater than 90% for both these agents. On the contrary, low susceptibility to fluoroquinolones even in the outpatient setting (84%) begins to bring into question the use of these agents as first line for infections commonly caused by E coli, such as urinary tract infections. Trimethoprimsulfamethoxazole susceptibility rates are below 80% in both inpatient and outpatient settings and should only be used for infections empirically in the context of supportive data from local antibiograms or definitive susceptibility data. In our multivariate model, increasing age was independently associated with reduced susceptibility to fluoroquinolones, nitrofurantoin, ceftriaxone, cefepime, gentamicin and ESBL production. The association between age and fluoroquinolone susceptibility has been demonstrated previously and is likely due to increasing exposure to fluoroquinolones over time and avoidance of fluoroquinolone use in children Predictably, inpatient isolates had lower susceptibility to several antibiotics, including amoxicillin-clavulanate, fluoroquinolones, cefazolin and trimethoprim-sulfamethoxazole. Interestingly, susceptibility to antimicrobials commonly used in the inpatient setting (ceftriaxone, cefepime, gentamicin, carbapenems and piperacillin-tazobactam) did not appear to be significantly affected by inpatient status. This is reassuring in that these antimicrobials maintain good activity overall in the hospital setting. The reason that antimicrobials commonly used in the community are most affected by inpatient status is not known, but may be due to general practitioners using these antimicrobials to treat outpatients and selection bias occurring because poor response due to antimicrobial resistance requires admission for parenteral antimicrobials. Interestingly, sex was not a predictor of susceptibility to any of the antimicrobials tested after adjusting for other factors in the multivariate model. Although large differences were seen between susceptibility to fluoroquinolones, both inpatient status and age appeared to be confounding factors in the effect of sex on fluoroquinolone resistance. The absence of a sex effect contradicts the findings of others Meropenem, ertapenem, piperacillin-tazobactam, tigecycline and cefoxitin were not significantly associated with any demographic variable in the multivariate model. Low overall resistance rates accounts for these observations. Our study had some limitations. We could not collect patient information such as length of stay, previous antimicrobial exposure and underlying disease. Although of great interest for the prediction of antimicrobial resistance, the effect of these variables cannot be determined with our data. Also, our isolates reflect only information from the 12 centres studied and our data may not reflect the antimicrobial susceptibility patterns of all hospitals in Canada. However, this study does provide valuable information about the factors predicting antimicrobial susceptibility of E coli in one of the largest of inpatient and outpatient populations in Canada studied to date

Epidemiology of vancomycin-resistant enterococci in Canadian hospitals (CANWARD study, 2007 to 2013)

Of 1,927 Enterococcus species isolates collected across Canada from 2007 to 2013, 80 (4.2%) were identified as vancomycin-resistant enterococci (VRE). VRE infections during this time tripled in Canadian hospitals, from 1.8% to 6.0% (P = 0.03). All VRE were Enterococcus faecium, with 90% possessing vanA. The prevalence of vanB decreased from 37.5% in 2007 to 0% in 2013 (P < 0.05). The VRE were multidrug resistant, but 70.6%, 86.3%, and 100% were susceptible to doxycycline, linezolid, and daptomycin, respectively

Analysis of 1560 Inpatient and Outpatient Escherichia coli Isolates from across Canada—Results from the CANWARD 2007 Study

OBJECTIVES: Escherichia coli was the most common pathogen isolated in the Canadian Ward Surveillance Study (CANWARD 2007) and remains one of the most common pathogens isolated in all health care settings. An in-depth analysis of all E coli isolates was performed to determine the distribution and demographics associated with resistance to antimicrobials, presence of extended-spectrum beta-lactamases (ESBLs) and multidrug resistance (MDR; concurrent resistance to agents from three or more different antimicrobial classes). METHODS: The CANWARD 2007 study characterized pathogens isolated from inpatient (surgical and medical wards, and intensive care units) and outpatient (emergency departments and clinics) areas of 12 Canadian hospitals between January and December 2007. E coli susceptibility to 12 antimicrobials was determined, ESBL production was determined, and a multivariate nominal logistic regression model was designed to determine if sex, isolation from a sterile site, inpatient versus outpatient status, and age were significantly associated with susceptibility to the tested antimicrobials, MDR or ESBL production. RESULTS: In total, 1702 E coli isolates, representing 21.6% of all isolates collected in the CANWARD 2007 study, were investigated. Of these, 1560 isolates fell within the primary objective of the study and were included in the present analysis. Susceptibilities were greater than 90% for meropenem (100%), ertapenem (100%), tigecycline (99.9%), piperacillin-tazobactam (97.9%), cefepime (97.9%), ceftriaxone (95.4%), nitrofurantoin (95.2%), cefoxitin (94.8%), amoxicillinclavulanate (92.9%) and gentamicin (91.4%). Cefazolin (89.4%), the fluoroquinolones (ciprofloxacin, 79.4%; levofloxacin, 79.9%) and trimethoprim-sulfamethoxazole (75.7%) were less active agents. In the multivariate model, invasive isolates were significantly associated with lower susceptibility rates for trimethoprim-sulfamethoxazole. Increasing age was associated with lower susceptibility to fluoroquinolones, ceftriaxone, cefepime, gentamicin and nitrofurantoin, as well as ESBL production. Sex was not associated with resistance to any antimicrobial or to ESBL production. Inpatient status was associated with higher resistance rates to amoxicillin-clavulanate, cefazolin, fluoroquinolones and trimethoprim-sulfamethoxazole. Isolation of an ESBL producer was only found to be independently associated with age, being more common in older patients. MDR was not found to be associated with any variable measured when ESBL producers were excluded from analysis. CONCLUSIONS: E coli antimicrobial susceptibility varies according to patient factors. Age and inpatient status were the most important determinants in the present analysis and should be considered when prescribing empirical antimicrobial therapy. Fluoroquinolones and sulfonamides should be used cautiously and in consideration of local resistance patterns for infections caused by E coli, due to lower susceptibility rates. Independent factors associated with antimicrobial resistance were age, inpatient status and isolation from a sterile site. These factors should be considered when empirically treating infections likely caused by E coli. Local antimicrobial prescribing practices, in particular the liberal use of fluoroquinolones, and inadequate infection control practices may be reducing susceptibility rates

Characterization of methicillin-resistant Staphylococcus aureus, vancomycin-resistant enterococci and extended-spectrum beta-lactamase-producing Escherichia coli in intensive care units in Canada: Results of the Canadian National Intensive Care Unit (CAN-ICU) study (2005–2006)

BACKGROUND: Methicillin-resistant Staphylococcus aureus (MRSA), extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli and vancomycin-resistant enterococci (VRE) are important hospital pathogens in Canada and worldwide

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

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

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 susceptibility testing. 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.Peer Reviewe

Antimicrobial Susceptibility of 6685 Organisms Isolated from Canadian Hospitals: CANWARD 2007

BACKGROUND: Antimicrobial resistance is a growing problem in North American hospitals as well as hospitals worldwide. OBJECTIVES: To assess the antimicrobial susceptibility patterns of commonly used agents against the 20 most common organisms isolated from Canadian hospitals. METHODS: In total, 7881 isolates were obtained between January 1, 2007, and December 31, 2007, from 12 hospitals across Canada as part of the Canadian Ward Surveillance Study (CANWARD 2007). Of these, 6685 isolates (20 most common organisms) obtained from bacteremic, urinary, respiratory and wound specimens underwent antimicrobial susceptibility testing. Susceptibility testing was assessed using the Clinical and Laboratory Standards Institute broth microdilution method. RESULTS: The most active (based upon minimum inhibitory concentration [MIC] data only) agents against methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-resistant Staphylococcus epidermidis (MRSE) were dalbavancin, daptomycin, linezolid, telavancin, tigecycline and vancomycin, with MICs required to inhibit the growth of 90% of organisms (MIC90) of 0.06 μg/mL and 0.06 μg/mL, 0.25 μg/mL and 0.25 μg/mL, 4 μg/mL and 1 μg/mL, 0.25 μg/mL and 0.25 μg/mL, 0.5 μg/mL and 0.25 μg/mL, and 1 μg/mL and 2 μg/mL, respectively. The most active agents against vancomycin-resistant enterococci were daptomycin, linezolid and tigecycline with MIC90s of 2 μg/mL, 4 μg/mL and 0.12 μg/mL, respectively. The most active agents against Escherichia coli were amikacin, cefepime, ertapenem, meropenem, piperacillin-tazobactam and tigecycline with MIC90s of 4 μg/mL, 2 μg/mL, 0.06 μg/mL or less, 0.12 μg/mL or less, 4 μg/mL and 1 μg/mL, respectively. The most active agents against extendedspectrum beta-lactamase-producing E coli were ertapenem, meropenem and tigecycline with MIC90s of 0.12 μg/mL or less, 0.12 μg/mL or less and 1 μg/mL, respectively. The most active agents against Pseudomonas aeruginosa were amikacin, cefepime, meropenem and piperacillin-tazobactam with MIC90s of 32 μg/mL, 32 μg/mL, 8 μg/mL and 64 μg/mL, respectively. The most active agents against Stenotrophomonas maltophilia were tigecycline and trimethoprimsulfamethoxazole and levofloxacin with MIC90s of 8 μg/mL, 8 μg/mL and 8 μg/mL, respectively. The most active agents against Acinetobacter baumannii were amikacin, fluoroquinolones (eg, levofloxacin), meropenem, and tigecycline with MIC90s of 2 μg/mL or less, 1 μg/mL, 4 μg/mL and 2 μg/mL, respectively. CONCLUSIONS: The most active agents versus Gram-positive cocci from Canadian hospitals were vancomycin, linezolid, daptomycin, tigecycline, dalbavancin and telavancin. The most active agents versus Gram-negative bacilli from Canadian hospitals were amikacin, cefepime, ertapenem (not P aeruginosa), meropenem, piperacillintazobactam and tigecycline (not P aeruginosa). Colistin (polymyxin E) was very active against P aeruginosa and A baumannii