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Background Understanding the burden of influenza is necessary to optimize recommendations for influenza vaccination. We describe the epidemiology of severe influenza in 50- to 64-year-old residents of metropolitan Toronto and Peel region, Canada, over 7 influenza seasons. Methods Prospective population-based surveillance for hospitalization associated with laboratory-confirmed influenza was conducted from September 2010 to August 2017. Conditions increasing risk of influenza complications were as defined by Canada's National Advisory Committee on Immunization. Age-specific prevalence of medical conditions was estimated using Ontario health administrative data. Population rates were estimated using Statistics Canada data. Results Over 7 seasons, 1228 hospitalizations occurred in patients aged 50–64 years: 40% due to A(H3N2), 30% A(H1N1), and 22% influenza B. The average annual hospitalization rate was 15.6, 20.9, and 33.2 per 100 000 in patients aged 50–54, 55–59, and 60–64 years, respectively; average annual mortality was 0.9/100 000. Overall, 33% of patients had received current season influenza vaccine; 963 (86%) had ≥1 underlying condition increasing influenza complication risk. The most common underlying medical conditions were chronic lung disease (38%) and diabetes mellitus (31%); 25% of patients were immunocompromised. The average annual hospitalization rate was 6.1/100 000 in those without and 41/100 000 in those with any underlying condition, and highest in those with renal disease or immunocompromise (138 and 281 per 100 000, respectively). The case fatality rate in hospitalized patients was 4.4%; median length of stay was 4 days (interquartile range, 2–8 days). Conclusions The burden of severe influenza in 50- to 64-year-olds remains significant despite our universal publicly funded vaccination program. These data may assist in improving estimates of the cost-effectiveness of new strategies to reduce this burden. [ABSTRACT FROM AUTHOR]

In multivariable analysis of associations between initial antibiotic therapy and clinical outcomes in 5005 patients with microbiologically confirmed Streptococcus pneumoniae infections,"discordant" empiric antibiotic therapy was not associated with 30-day mortality rate (hazard ratio, 0.94; 95% confidence interval, .67-1.32). [ABSTRACT FROM AUTHOR]

Vancomycin-variable enterococci (VVE) are vanA-positive, vancomycin-susceptible enterococci with the ability to revert to a vancomycin-resistant phenotype on exposure to vancomycin. We sought to assess the prevalence of VVE and to determine clinical characteristics of patients infected with VVE. We prospectively collected Enterococcus faecium sterile site isolates from Toronto Invasive Bacterial Diseases Network hospitals from January 2015 to June 2016 and calculated VVE (defined as vanA-positive, vancomycin-susceptible isolates) prevalence among vanA-containing isolates. We performed chart reviews of VVE and vancomycin-resistant E. faecium (VRE) bacteremias identified from January 2012 to June 2016, and on a random sample of patients with bacteremia due to vanA/vanB-negative, vancomycin-susceptible enterococci (VSE) from January 2015 to June 2016. Clinical characteristics were compared and factors associated with mortality assessed. Because of the potential reversion from VVE to VRE, pulsed-field gel electrophoresis (PFGE) was performed for strains causing breakthrough bacteremia in order to identify relatedness among strains with different phenotypic resistance within the same patient. VVE comprised 47% (18/38) of vanA-positive isolates. The charts of 36 VRE, 25 VVE, and 79 VSE patients were reviewed. Central venous catheter associated bacteremia was more common in VVE (44%) and VRE patients (57%) than in VSE patients (28%) (P = 0.01). The Pitt bacteremia (OR 1.3, P = 0.002) and the Charlson score (OR 1.2, P = 0.008) were the only independent mortality predictors. PFGE of strains causing breakthrough bacteremia showed high within-patient clonality, irrespective of vanA-positivity or vancomycin-susceptibility. A substantial proportion of vanA-positive isolates are VVE and are therefore not detected with conventional selective culture methods. Bacteremia sources of patients with VVE are similar to those infected with VRE. We detected no association between VVE and 30-day mortality or breakthrough bacteremia. [ABSTRACT FROM AUTHOR]

Background: Identification of high-risk populations for serious infection due to S. pneumoniae will permit appropriately targeted prevention programs. Methods: We conducted prospective, population-based surveillance for invasive pneumococcal disease and laboratory confirmed pneumococcal pneumonia in homeless adults in Toronto, a Canadian city with a total population of 2.5 M, from January 1, 2002 to December 31, 2006. Results: We identified 69 cases of invasive pneumococcal disease and 27 cases of laboratory confirmed pneumococcal pneumonia in an estimated population of 5050 homeless adults. The incidence of invasive pneumococcal disease in homeless adults was 273 infections per 100,000 persons per year, compared to 9 per 100,000 persons per year in the general adult population. Homeless persons with invasive pneumococcal disease were younger than other adults (median age 46 years vs 67 years, P<.001), and more likely than other adults to be smokers (95% vs. 31%, P<.001), to abuse alcohol (62% vs 15%, P<.001), and to use intravenous drugs (42% vs 4%, P<.001). Relative to age matched controls, they were more likely to have underlying lung disease (12/69, 17% vs 17/272, 6%, P = .006), but not more likely to be HIV infected (17/69, 25% vs 58/282, 21%, P = .73). The proportion of patients with recurrent disease was five fold higher for homeless than other adults (7/58, 12% vs. 24/ 943, 2.5%, P<.001). In homeless adults, 28 (32%) of pneumococcal isolates were of serotypes included in the 7-valent conjugate vaccine, 42 (48%) of serotypes included in the 13-valent conjugate vaccine, and 72 (83%) of serotypes included in the 23-valent polysaccharide vaccine. Although no outbreaks of disease were identified in shelters, there was evidence of clustering of serotypes suggestive of transmission of pathogenic strains within the homeless population. Conclusions: Homeless persons are at high risk of serious pneumococcal infection. Vaccination, physical structure changes or other program to reduce transmission in shelters, harm reduction programs to reduce rates of smoking, alcohol abuse and infection with bloodborne pathogens, and improved treatment programs for HIV infection may all be effective in reducing the risk. [ABSTRACT FROM AUTHOR]

Background In Ontario, Canada, PCV13 is covered for immunocompromised (IC) adults over 50y. PCV13 programs are thought not to be cost-effective in other adults because it is assumed that herd immunity from pediatric vaccination programs (PCV7 since 2005; PCV13 since 2010) will reduce PCV13 disease burden dramatically in adults. We analyzed data from the Toronto Invasive Bacterial Diseases Network (TIBDN) to ask whether PCV13-type invasive pneumococcal disease (IPD) in adults persists in our population. Methods TIBDN performs population-based surveillance for IPD in Toronto+Peel Region, Ontario (pop4.1M). All microbiology laboratories receiving specimens from residents report cases of IPD and submit isolates to a central study lab for serotyping; annual audits are conducted. Demographic, medical and vaccination information are obtained from patients, families and physicians. Population data are from Statistics Canada. Results Since 1995, 10,365 episodes of IPD have been identified; detailed medical information was available for 9,801 (95%) and serotyping for 9411 (91%). Among 8658 adult cases, 4,273 (49%) were in those aged 15–64 years, and 4,285 (51%) in those aged >645 years. The most common diagnoses were pneumonia (5,978/8,025, 74%) and bacteremia without focus (1,030, 13%); 470 (4.6%) cases had meningitis; the case fatality rate (CFR) was 21%. The incidence of disease due to STs in PCV13 in adults declined from 7.0/100,000/year 2001 to 2.9/100,000/year in 2015–2018 and was stable from 2015–2018 (Figure 1). The incidence was > 5/100,000/year in non-IC patients over 65 years, and younger patients with cancer and kidney disease (Figure 2). In IPD from 2015 to 2018, adult patients with PCV13 ST disease were younger (median age 64 years vs. 67 years, P =.03) than other patients; there was no significant difference in the proportion with at least one underlying chronic condition (253, 69% PCV13ST, vs. 541,74% other ST, P = 0.08), or in CFR (59, 16% PCV13 vs. 145, 20% other, P = 0.13). The ST distribution of cases due to PCV13 STs is shown in Figure 3. Conclusion A significant burden of IPD due to PCV13 serotypes persists in adults in our population despite 8 years of routine pediatric PCV13 vaccination. This burden needs to be considered in assessing the value and cost-effectiveness of PCV programs for adults. Disclosures All authors: No reported disclosures. [ABSTRACT FROM AUTHOR]

Background. Background Invasive Group A streptococcal (iGAS) infections remain a substantial source of morbidity and mortality. We explore the clinical and molecular epidemiology of iGAS infections in Toronto, Ontario, Canada over a 26-year period. Methods The Toronto Invasive Bacterial Diseases Network has performed population-based surveillance for iGAS infections in metropolitan Toronto and Peel regions since 1992. Participating microbiology laboratories report and submit sterile site specimens for central processing. M typing was performed on iGAS isolates until September 2006; thereafter emm typing was performed. Clinical information was collected by chart review using standardized collection forms. Results Over the 26-year period there were 2819 iGAS infections, representing an average incidence of 2.85 per 100,000 residents with a nadir of 1.65 in 1993 and a peak of 4.52 in 2014. Nosocomial infections occurred in 8.9% (251/2,819). There was substantial variation in annual incidence rates over the study period with increases from 1992 until 2002 and then 2004 until 2014 (analysis for trend, P < 0.001). Skin and soft-tissue infections were the most common clinical presentation, accounting for 33.2% (936/2,819), followed by bacteremia without a focus in 15.4% (435/2,819). Necrotizing fasciitis was observed in 7.4% (208/2,819) and criteria for toxic shock syndrome were met in 17.6% (497/2,819). Overall case fatality within 30 days of hospitalization was 15.3% (95% confidence interval 14.0 to 16.6) and did not change over time. M serotype distribution varied yearly with the most common type being M1 at 22.2% (626/2,189) followed by M12 at 8.2% (230/2,189), then M89 at 5.8% (163/2,189). Antibiotic susceptibility was available from 1998 onwards with overall clindamycin susceptibility at 92.3% (1,957/2,121) and erythromycin susceptibility at 87.9% (1864/2,121). Conclusion The incidence of iGAS in Toronto, Ontario has varied over time, with no recent increase apparent. Similar to worldwide observations, M1 serotype was the most commonly isolated; most common serotypes demonstrated cyclical variation. Case fatality rates have remained relatively constant making the development of a vaccine imperative. Disclosures All authors: No reported disclosures. [ABSTRACT FROM AUTHOR]

Background The number of invasive group A Streptococcus (iGAS) infections due to hitherto extremely rare type emm74 strains has increased in several Canadian provinces since late 2015. We hypothesized that the cases recorded in the different provinces are linked and caused by strains of an emm74 clone that recently emerged and expanded explosively. Methods We analyzed both active and passive surveillance data for iGAS infections and used whole-genome sequencing to investigate the phylogenetic relationships of the emm74 strains responsible for these invasive infections country-wide. Results Genome analysis showed that highly clonal emm74 strains, genetically different from emm74 organisms previously circulating in Canada, were responsible for a country-wide epidemic of >160 invasive disease cases. The emerging clone belonged to multilocus sequence typing ST120. The analysis also revealed dissemination patterns of emm74 subclonal lineages across Canadian provinces. Clinical data analysis indicated that the emm74 epidemic disproportionally affected middle-aged or older male individuals. Homelessness, alcohol abuse, and intravenous drug usage were significantly associated with invasive emm74 infections. Conclusions In a period of 20 months, an emm74 GAS clone emerged and rapidly spread across several Canadian provinces located more than 4500 km apart, causing invasive infections primarily among disadvantaged persons. [ABSTRACT FROM AUTHOR]