Measuring waning protection from seasonal influenza vaccination during nine influenza seasons, Ontario, Canada, 2010/11 to 2018/19

BackgroundWaning immunity from seasonal influenza vaccination can cause suboptimal protection during peak influenza activity. However, vaccine effectiveness studies assessing waning immunity using vaccinated and unvaccinated individuals are subject to biases.AimWe examined the association between time since vaccination and laboratory-confirmed influenza to assess the change in influenza vaccine protection over time.MethodsUsing linked laboratory and health administrative databases in Ontario, Canada, we identified community-dwelling individuals aged ≥ 6 months who received an influenza vaccine before being tested for influenza by RT-PCR during the 2010/11 to 2018/19 influenza seasons. We estimated the adjusted odds ratio (aOR) for laboratory-confirmed influenza by time since vaccination (categorised into intervals) and for every 28 days.ResultsThere were 53,065 individuals who were vaccinated before testing for influenza, with 10,264 (19%) influenza-positive cases. The odds of influenza increased from 1.05 (95% CI: 0.91-1.22) at 42-69 days after vaccination and peaked at 1.27 (95% CI: 1.04-1.55) at 126-153 days when compared with the reference interval (14-41 days). This corresponded to 1.09-times increased odds of influenza every 28 days (aOR = 1.09; 95% CI: 1.04-1.15). Individuals aged 18-64 years showed the greatest decline in protection against influenza A(H1N1) (aORper 28 days = 1.26; 95% CI: 0.97-1.64), whereas for individuals aged ≥ 65 years, it was against influenza A(H3N2) (aORper 28 days = 1.20; 95% CI: 1.08-1.33). We did not observe evidence of waning vaccine protection for individuals aged < 18 years.ConclusionsInfluenza vaccine protection wanes during an influenza season. Understanding the optimal timing of vaccination could ensure robust protection during seasonal influenza activity.

Predictors of later COVID-19 test seeking

Background

Delays in COVID-19 testing may increase the risk of secondary household and community transmission. Little is known about what patient characteristics and symptom profiles are associated with delays in test seeking.

Methods

We conducted a retrospective cohort study of all symptomatic patients diagnosed with COVID-19 and assessed in a COVID Expansion to Outpatients (COVIDEO) virtual care program between March 2020 and June 2021. The primary outcome was later test seeking more than 3 days from symptom onset. Multivariable logistic regression was used to examine predictors of later testing including patient characteristics and symptoms (30 individual symptoms or 7 symptom clusters).

Results

Of 5,363 COVIDEO patients, 4,607 were eligible and 2,155/4,607 (46.8%) underwent later testing. Older age was associated with increased odds of late testing (adjusted odds ratio [aOR] 1.007/year; 95% CI 1.00 to 1.01), as was history of recent travel (aOR 1.4; 95% CI 1.01 to 1.95). Health care workers had lower odds of late testing (aOR 0.50; 95% CI 0.39 to 0.62). Late testing was associated with symptoms in the cardiorespiratory (aOR 1.2; 95% CI 1.05, 1.36), gastrointestinal (aOR = 1.2; 95% CI 1.04, 1.4), neurological (aOR 1.1; 95% CI 1.003, 1.3) and psychiatric (aOR 1.3; 95% CI 1.1, 1.5) symptom clusters. Among individual symptoms, dyspnea, anosmia, dysgeusia, sputum, and anorexia were associated with late testing; pharyngitis, myalgia, and headache were associated with early testing.

Conclusion

Certain patient characteristics and symptoms are associated with later testing, and warrant further efforts to encourage earlier testing to minimize transmission.

Evaluating the impact of a virtual outpatient care program in preventing hospitalizations, emergency department visits and mortality for patients with COVID-19: a matched cohort study

OBJECTIVES

We sought to evaluate the impact of virtual care in preventing unnecessary healthcare visits for SARSCoV-2 patients.

METHODS

We conducted a retrospective matched cohort study, evaluating the COVID-19 Expansion to Outpatients (COVIDEO) program involving virtual assessments for all positive patients in the Sunnybrook assessment center from January 2020 to June 2021, followed by risk-stratified routine follow-up, couriering of oxygen saturation devices, and 24 hour/day direct-to-physician pager for urgent questions. We linked COVIDEO data to province-wide datasets, matching each eligible COVIDEO patient to ≤10 other Ontario SARS-CoV-2 patients on age, sex, neighborhood, and date. The primary outcome was emergency department (ED) visit, hospitalization or death within 30 days. Multivariable regression accounted for comorbidities, vaccination and pre-pandemic healthcare utilization.

RESULTS

Among 6,508 eligible COVIDEO patients, 4,763 (73.1%) were matched to ≥1 non-COVIDEO patient. COVIDEO care was protective against the primary composite outcome (adjusted odds ratio (aOR) 0.91, 95%CI 0.82-1.02), with a reduction in ED visits (7.8% vs 9.6%; aOR 0.79, 95%CI 0.70-0.89), but increase in hospitalizations (3.8% vs 2.7%, aOR 1.37, 95%CI 1.14-1.63) reflecting more direct-to-ward admissions (1.3% vs 0.2%, p < 0.0001). Results were similar when matched comparators were limited to patients who had not received virtual care elsewhere with a decrease in ED visits (7.8 vs. 8.6%, aOR 0.86, 95%CI 0.75-0.99) and an increase in hospitalizations (3.7 vs 2.4%, aOR 1.45, 95%CI 1.17-1.80).

CONCLUSIONS

An intensive remote care program can prevent unnecessary ED visits and facilitate direct-to-ward hospitalizations and thereby mitigate the impact of COVID-19 on the healthcare system.

Prevalence and predictors of persistent post-COVID-19 symptoms

BACKGROUND

The pandemic has affected hundreds of millions of people; early reports suggesting high rates of prolonged symptoms may be prone to selection bias.

METHODS

In a program caring for all SARS-CoV-2 positive inpatients and outpatients between March to October 2020, and offering universal 90-day follow-up, we compared those who died prior to 90 days, not responding to follow-up, declining, or accepting follow-up. Among those seen or declining follow-up, we determined the prevalence and predictors of persistent symptoms.

RESULTS

Among 993 patients, 21 (2.1%) died prior to 90 days, 506 (50.9%) did not respond, 260 (26.1%) declined follow-up because they were well, and 206 (20.7%) were fully assessed. Of 466 who responded to follow-up inquiry, 133 (28.5%) reported ≥1 persistent symptom, including constitutional (15.5%), psychiatric (14.2%), rheumatologic (13.1%), neurologic (13.1%), cardiorespiratory (12.0%), and gastrointestinal (1.7%). Predictors differed for each symptom type. Any persistent symptom was more common in older patients (adjusted odds ratio [aOR] 1.11, 95% CI 1.04 to 1.18/5 years), those diagnosed in hospital (aOR 2.03, 95% CI 1.24 to 3.33) and those with initial constitutional and rheumatologic symptoms. Patients not responding to follow-up were younger and healthier at baseline.

CONCLUSION

Persistent symptoms are common and diverse 3 months post-COVID-19 but are likely over-estimated by most reports.

Association between initial symptoms and subsequent hospitalization in outpatients with COVID-19: A cohort study

BACKGROUND

Most individuals with coronavirus disease 2019 (COVID-19) experience mild symptoms and are managed in the outpatient setting. The aim of this study was to determine whether self-reported symptoms at the time of diagnosis can identify patients at risk of clinical deterioration.

METHODS

This was a retrospective cohort study of 671 outpatients with laboratory-confirmed COVID-19 diagnosed in Toronto between March 1 and October 16, 2020. We examined the association between patients' baseline characteristics and self-reported symptoms at the time of diagnosis and the risk of subsequent hospitalization.

RESULTS

Of 671 participants, 26 (3.9%) required hospitalization. Individuals aged 65 years or older were more likely to require hospitalization (odds ratio [OR] 5.29, 95% CI 2.19 to 12.77), whereas those without medical comorbidities were unlikely to be hospitalized (OR 0.02, 95% CI 0.00 to 0.17). After adjusting for age and presence of comorbidities, sputum production (adjusted OR [aOR] 5.01, 95% CI 1.97 to 12.75), arthralgias (aOR 4.82, 95% CI 1.85 to 12.53), diarrhea (aOR 4.56, 95% CI 1.82 to 11.42), fever (aOR 3.64, 95% CI 1.50 to 8.82), chills (aOR 3.62, 95% CI 1.54 to 8.50), and fatigue (aOR 2.59, 95% CI 1.04 to 6.47) were associated with subsequent hospitalization.

CONCLUSIONS

Early assessment of symptoms among outpatients with COVID-19 can help identify individuals at risk of clinical deterioration. Additional studies are needed to determine whether more intense follow-up and early intervention among high-risk individuals can alter the clinical trajectory of and outcomes among outpatients with COVID-19.

Impact of a Comprehensive Antimicrobial Stewardship Program on Institutional Burden of Antimicrobial Resistance: A 14-Year Controlled Interrupted Time-series Study

BACKGROUND

Antimicrobial resistance (AMR) constitutes an international public health threat widely believed to result from excessive antimicrobial use (AMU). Numerous authorities have recommended antimicrobial stewardship programs (ASPs) to curb the selection of AMR, but there is a lack of data confirming this benefit.

METHODS

A controlled interrupted time-series study spanning 14 years was performed to assess impact of a comprehensive hospital-based ASP that included pharmacist-led audit and feedback on institutional AMR. Patient-level microbiologic and AMU data were obtained from October 2002 to September 2016. Poisson regression models were used to identify changes in the incidence and trend of hospital-acquired (HA) antibiotic-resistant organisms (AROs) and multidrug-resistant organisms (MDROs). Changes in community-acquired (CA)-ARO, CA-MDRO, and inpatient AMU were assessed as controls and process outcomes.

RESULTS

Statistically significant shifts in AMU, HA-ARO, and HA-MDRO trends coinciding with ASP implementation were observed, corresponding with a 9% reduction in HA-ARO burden (incidence rate ratio [IRR], 0.91 [95% confidence interval {CI}, .83-.99]; P = .03) and a 13% reduction in HA-MDRO burden (IRR, 0.87 [95% CI, .73-1.04]; P = .13) in the intervention period. In contrast, CA-ARO and CA-MDRO incidence continued to rise, with 40% (IRR, 1.40 [95% CI, 1.28-1.54]; P < .0001) and 68% (IRR, 1.68 [95% CI, 1.57-1.82]; P < .0001) increases in burden found, respectively.

CONCLUSIONS

Implementation of a comprehensive ASP resulting in reduced AMU was associated with a significant reduction in institutional AMR, even though community AMR increased during the same period. These results confirm that ASPs play an important role in the fight against AMR.

Dissemination of Verona Integron-encoded Metallo-β-lactamase among clinical and environmental Enterobacteriaceae isolates in Ontario, Canada

Surveillance data from Southern Ontario show that a majority of Verona Integron-encoded Metallo-β-lactamase (VIM)-producing Enterobacteriaceae are locally acquired. To better understand the local epidemiology, we analysed clinical and environmental bla_VIM-positive Enterobacteriaceae from the area. Clinical samples were collected within the Toronto Invasive Bacterial Diseases Network (2010–2016); environmental water samples were collected in 2015. We gathered patient information on place of residence and hospital admissions prior to the diagnosis. Patients with and without plausible source of acquisition were compared regarding risk exposures. Microbiological isolates underwent whole-genome sequencing (WGS); bla_VIM carrying plasmids were characterized. We identified 15 patients, thereof 11 with bla_VIM-1-positive Enterobacter hormaechei within two genetic clusters based on WGS. Whereas no obvious epidemiologic link was identified among cluster I patients, those in cluster II were connected to a hospital outbreak. Except for patients with probable acquisition abroad, we did not identify any further risk exposures. Two bla_VIM-1-positive E. hormaechei from environmental waters matched with the clinical clusters; plasmid sequencing suggested a common ancestor plasmid for the two clusters. These data show that both clonal spread and horizontal gene transfer are drivers of the dissemination of bla_VIM-1-carrying Enterobacter hormaechei in hospitals and the aquatic environment in Southern Ontario, Canada.

The impact of repeated vaccination using 10-year vaccination history on protection against influenza in older adults: a test-negative design study across the 2010/11 to 2015/16 influenza seasons in Ontario, Canada

Introduction

Annual influenza vaccination is recommended for older adults, but evidence regarding the impact of repeated vaccination has been inconclusive.

Aim

We investigated vaccine effectiveness (VE) against laboratory-confirmed influenza and the impact of repeated vaccination over 10 previous seasons on current season VE among older adults.

Methods

We conducted an observational test-negative study in community-dwelling adults aged > 65 years in Ontario, Canada for the 2010/11 to 2015/16 seasons by linking laboratory and health administrative data. We estimated VE using multivariable logistic regression. We assessed the impact of repeated vaccination by stratifying by previous vaccination history.

Results

We included 58,304 testing episodes for respiratory viruses, with 11,496 (20%) testing positive for influenza and 31,004 (53%) vaccinated. Adjusted VE against laboratory-confirmed influenza for the six seasons combined was 21% (95% confidence interval (CI): 18 to 24%). Patients who were vaccinated in the current season, but had received no vaccinations in the previous 10 seasons, had higher current season VE (34%; 95%CI: 9 to 52%) than patients who had received 1–3 (26%; 95%CI: 13 to 37%), 4–6 (24%; 95%CI: 15 to 33%), 7–8 (13%; 95%CI: 2 to 22%), or 9–10 (7%; 95%CI: −4 to 16%) vaccinations (trend test p = 0.001). All estimates were higher after correcting for misclassification of current season vaccination status. For patients who were not vaccinated in the current season, residual protection rose significantly with increasing numbers of vaccinations received previously.

Conclusions

Although VE appeared to decrease with increasing numbers of previous vaccinations, current season vaccination likely provides some protection against influenza regardless of the number of vaccinations received over the previous 10 influenza seasons.

Emergence of pstS-Null Vancomycin-Resistant Enterococcus faecium Clone ST1478, Canada, 2013-2018

Rates of vancomycin-resistant enterococci bloodstream infections have remained relatively low in Canada. We recently observed an increase of 113% in these infections rates, which coincided with emergence of Enterococcus faecium pstS-null sequence type 1478. The proportion of this sequence type increased from 2.7% to 38.7% for all tested isolates from 2013-2018.

Trends in health care-associated infections in acute care hospitals in Canada: an analysis of repeated point-prevalence surveys

BACKGROUND

Health care-associated infections are a common cause of patient morbidity and mortality. We sought to describe the trends in these infections in acute care hospitals, using data from 3 national point-prevalence surveys.

METHODS

The Canadian Nosocomial Infection Surveillance Program (CNISP) conducted descriptive point-prevalence surveys to assess the burden of health care-associated infections on a single day in February of 2002, 2009 and 2017. Surveyed infections included urinary tract infection, pneumonia, Clostridioides difficile infection, infection at surgical sites and bloodstream infections. We compared the prevalence of infection across the survey years and considered the contribution of antimicrobial-resistant organisms as a cause of these infections.

RESULTS

We surveyed 28 of 33 (response rate 84.8%) CNISP hospitals (6747 patients) in 2002, 39 of 55 (response rate 71.0%) hospitals (8902 patients) in 2009 and 47 of 66 (response rate 71.2%) hospitals (9929 patients) in 2017. The prevalence of patients with at least 1 health care-associated infection increased from 9.9% in 2002 (95% confidence interval [CI] 8.4%-11.5%) to 11.3% in 2009 (95% CI 9.4%-13.5%), and then declined to 7.9% in 2017 (95% CI 6.8%-9.0%). In 2017, device-associated infections accounted for 35.6% of all health care-associated infections. Methicillin-resistant Staphylococcus aureus (MRSA) accounted for 3.9% of all organisms identified from 2002 to 2017; other antibiotic-resistant organisms were uncommon causes of infection for all survey years.

INTERPRETATION

In CNISP hospitals, there was a decline in the prevalence of health care-associated infection in 2017 compared with previous surveys. However, strategies to prevent infections associated with medical devices should be developed. Apart from MRSA, few infections were caused by antibiotic-resistant organisms.

Sources of viral respiratory infections in Canadian acute care hospital healthcare personnel

BACKGROUND

Viral respiratory illnesses are common causes of outbreaks and can be fatal to some patients.

AIM

To investigate the association between laboratory-confirmed viral respiratory infections and potential sources of exposure during the previous 7 days.

METHODS

In this nested case-control analysis, healthcare personnel from nine Canadian hospitals who developed acute respiratory illnesses during the winters of 2010/11-2013/14 submitted swabs that were tested for viral pathogens. Associated illness diaries and the weekly diaries of non-ill participants provided information on contact with people displaying symptoms of acute respiratory illness in the previous week. Conditional logistic regression assessed the association between cases, who were matched by study week and site with controls with no respiratory symptoms.

FINDINGS

There were 814 laboratory-confirmed viral respiratory illnesses. The adjusted odds ratio (aOR) of a viral illness was higher for healthcare personnel reporting exposures to ill household members [7.0, 95% confidence interval (CI) 5.4-9.1], co-workers (3.4, 95% CI 2.4-4.7) or other social contacts (5.1, 95% CI 3.6-7.1). Exposures to patients with respiratory illness were not associated with infection (aOR 0.9, 95% CI 0.7-1.2); however, healthcare personnel with direct patient contact did have higher odds (aOR 1.3, 95% CI 1.1-1.6). The aORs for exposure and for direct patient contact were similar for illnesses caused by influenza.

CONCLUSION

Community and co-worker contacts are important sources of viral respiratory illness in healthcare personnel, while exposure to patients with recognized respiratory infections is not associated. The comparatively low risk associated with direct patient contact may reflect transmission related to asymptomatic patients or unrecognized infections.

Antimicrobial use among adult inpatients at hospital sites within the Canadian Nosocomial Infection Surveillance Program: 2009 to 2016

BACKGROUND

Antimicrobial resistance is a growing threat to the world's ability to prevent and treat infections. Links between quantitative antibiotic use and the emergence of bacterial resistance are well documented. This study presents benchmark antimicrobial use (AMU) rates for inpatient adult populations in acute-care hospitals across Canada.

METHODS

In this retrospective surveillance study, acute-care adult hospitals participating in the Canadian Nosocomial Infection Surveillance Program (CNISP) submitted annual AMU data on all systemic antimicrobials from 2009 to 2016. Information specific to intensive care units (ICUs) and non-ICU wards were available for 2014-2016. Data were analyzed using defined daily doses (DDD) per 1000 patient days (DDD/1000pd).

RESULTS

Between 2009 and 2016, 16-18 CNISP adult hospitals participated each year and provided their AMU data (22 hospitals participated in ≥1 year of surveillance; 11 in all years). From 2009 to 2016, there was a significant reduction in use (12%) (from 654 to 573 DDD/1000pd, p = 0.03). Fluoroquinolones accounted for the majority of this decrease (47% reduction in combined oral and intravenous use, from 129 to 68 DDD/1000pd, p < 0.002). The top five antimicrobials used in 2016 were cefazolin (78 DDD/1000pd), piperacillin-tazobactam (53 DDD/1000pd), ceftriaxone (49 DDD/1000pd), vancomycin (combined oral and intravenous use was 44 DDD/1000pd; 7% of vancomycin use was oral), and ciprofloxacin (combined oral and intravenous use: 42 DDD/1000pd). Among the top 10 antimicrobials used in 2016, ciprofloxacin and metronidazole use decreased significantly between 2009 and 2016 by 46% (p = 0.002) and 26% (p = 0.002) respectively. Ceftriaxone (85% increase, p = 0.0008) and oral amoxicillin-clavulanate (140% increase, p < 0.0001) use increased significantly but contributed only a small component (8.6 and 5.0%, respectively) of overall use.

CONCLUSIONS

This study represents the largest collection of dispensed antimicrobial use data among inpatients in Canada to date. Between 2009 and 2016, there was a significant 12% decrease in AMU, driven primarily by a 47% decrease in fluoroquinolone use. Modest absolute increases in parenteral ceftriaxone and oral amoxicillin-clavulanate use were noted but contributed a small amount of total AMU. Ongoing national surveillance is crucial for establishing benchmarks and antimicrobial stewardship guidelines.

2716. Persistence of 13-Valent Pneumococcal Conjugate Vaccine (PCV13) Serotypes in Invasive Pneumococcal Disease in Adults in Southern Ontario Canada Despite Routine Pediatric Vaccination

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.

462. Prospective Surveillance of Invasive Group A Streptococcal Infections in Toronto, Ontario, Canada: 1992–2017

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.

Influenza Vaccine Effectiveness Among Patients With Cancer: A Population-Based Study Using Health Administrative and Laboratory Testing Data From Ontario, Canada

PURPOSE

Seasonal influenza vaccination is recommended for patients with cancer despite concerns of disease or treatment-associated immunosuppression. The objective of this study was to evaluate vaccine effectiveness (VE) against laboratory-confirmed influenza for patients with cancer.

PATIENTS AND METHODS

We conducted an observational test-negative design study of previously diagnosed patients with cancer 18 years of age and older who underwent influenza testing during the 2010-2011 to 2015-2016 influenza seasons in Ontario, Canada. We linked individual-level cancer registry, respiratory virus testing, and health administrative data to identify the study population and outcomes. Vaccination status was determined from physician and pharmacist billing claims. We used multivariable logistic regression to estimate VE, adjusting for age, sex, rurality, income quintile, cancer characteristics, chemotherapy exposure, comorbidities, previous health care use, influenza season, and calendar time.

RESULTS

We identified 26,463 patients with cancer who underwent influenza testing, with 4,320 test-positive cases (16%) and 11,783 (45%) vaccinated. Mean age was 70 years, 52% were male, mean time since diagnosis was 6 years, 69% had solid tumor malignancies, and 23% received active chemotherapy. VE against laboratory-confirmed influenza was 21% (95% CI, 15% to 26%), and VE against laboratory-confirmed influenza hospitalization was 20% (95% CI, 13% to 26%). For patients with solid tumor malignancies, VE was 25% (95% CI, 18% to 31%), compared with 8% (95% CI, -5% to 19%) for patients with hematologic malignancies (P = .015). Active chemotherapy usage did not significantly affect VE, especially among patients with solid tumor cancer.

CONCLUSION

Our results support recommendations for influenza vaccination for patients with cancer. VE was decreased for patients with hematologic malignancies, and there was no significant difference in VE among patients with solid tumor cancer receiving active chemotherapy. Strategies to optimize influenza prevention among patients with cancer are warranted.

Emergence of Carbapenemase-Producing Enterobacteriaceae, South-Central Ontario, Canada1

We analyzed population-based surveillance data from the Toronto Invasive Bacterial Diseases Network to describe carbapenemase-producing Enterobacteriaceae (CPE) infections during 2007–2015 in south-central Ontario, Canada. We reviewed patients’ medical records and travel histories, analyzed microbiologic and clinical characteristics of CPE infections, and calculated incidence. Among 291 cases identified, New Delhi metallo-β-lactamase was the predominant carbapenemase (51%). The proportion of CPE-positive patients with prior admission to a hospital in Canada who had not received healthcare abroad or traveled to high-risk areas was 13% for patients with oxacillinase-48, 24% for patients with New Delhi metallo-β-lactamase, 55% for patients with Klebsiella pneumoniae carbapenemase, and 67% for patients with Verona integron-encoded metallo-β-lactamase. Incidence of CPE infection increased, reaching 0.33 cases/100,000 population in 2015. For a substantial proportion of patients, no healthcare abroad or high-risk travel could be established, suggesting CPE acquisition in Canada. Policy and practice changes are needed to mitigate nosocomial CPE transmission in hospitals in Canada.

Characteristics and Outcomes of Young Children Hospitalized With Laboratory-confirmed Influenza or Respiratory Syncytial Virus in Ontario, Canada, 2009-2014

BACKGROUND

Respiratory illnesses are a major contributor to pediatric hospitalizations, with influenza and respiratory syncytial virus (RSV) causing substantial morbidity and cost each season. We compared the characteristics and outcomes of children 0-59 months of age who were hospitalized with laboratory-confirmed influenza or RSV between 2009 and 2014 in Ontario, Canada.

METHODS

We included hospitalized children who were tested for influenza A, influenza B and RSV and were positive for a single virus. We characterized individuals by their demographics and healthcare utilization patterns and compared their hospital outcomes, in-hospital cost and postdischarge healthcare use by virus type and by presence of underlying comorbidities.

RESULTS

We identified and analyzed 7659 hospitalizations during which a specimen tested positive for influenza or RSV. Children with RSV were the youngest whereas children with influenza B were the oldest [median ages 6 months (interquartile range: 2-17 months) and 25 months (interquartile range: 10-45 months), respectively]. Complex chronic conditions were more prevalent among children with all influenza (sub)types than RSV (31%-34% versus 20%). In-hospital outcomes were similar by virus type, but in children with comorbidities, postdischarge outcomes varied. We observed no differences in in-hospital cost between viruses or by presence of comorbidities [overall median cost: $4150 Canadian dollars (interquartile range: $3710-$4948)].

CONCLUSIONS

Influenza and RSV account for large numbers of pediatric hospitalizations. RSV and influenza were similar in terms of severity and cost in hospitalized children. Influenza vaccination should be promoted in pregnant women and young children, and a vaccine against RSV would mitigate the high burden of RSV.

Steady-State Pharmacokinetics of Oral Ciprofloxacin in Continuous Cycling Peritoneal Dialysis Patients: Brief Report

Steady-state pharmacokinetics of oral ciprofloxacin in 3 continuous cycling peritoneal dialysis (CCPD) outpatients given ciprofloxacin 750 mg b.i.d. for 5 doses was determined. Mean steady-state maximum serum concentration and half-life were 4.4 ± 1.5 mg/L and 10.3 ± 2.6 hours, respectively. Mean maximum dialysate concentration in the daytime long dwell and overnight continuous cycling dwell were 7.4 ± 1.2 mg/L and 3.3 ± 1.2 mg/L, respectively. Oral ciprofloxacin 750 mg b.i.d. may be reasonable for bloodstream and peritoneal infections caused by susceptible bacteria in CCPD patients.

Using routinely collected laboratory and health administrative data to assess influenza vaccine effectiveness: introducing the Flu and Other Respiratory Viruses Research (FOREVER) Cohort

IntroductionAnnual evaluation of influenza vaccine effectiveness (VE) is required because of frequent changes to circulating and vaccine strains. Traditionally, VE studies enroll patients who fulfill case definitions for respiratory infections and are tested for influenza. VE estimates generated from convenience samples of routinely collected specimens might be biased. Objectives and ApproachWe assessed the validity of using data from respiratory specimens collected during clinical encounters to estimate VE. We created the Flu and Other Respiratory Viruses Research (FOREVER) Cohort by linking respiratory virus laboratory test results from 2009-2014 from 11 public health and 8 hospital laboratories across Ontario to health administrative databases, including databases with billing claims for physician- and pharmacist-administered influenza vaccines. We evaluated the presence of information and selection biases when using these data and estimated VE in community-dwelling older adults (>65) using the test-negative design under conditions that emulated the inclusion criteria in traditional VE studies. ResultsThe FOREVER Cohort included test results from 283,711 respiratory specimens obtained from 216,730 individuals. The overall linkage proportion to health administrative databases using deterministic and probabilistic linkage methods was 97.5%. Influenza positivity for older adults with unknown lag between illness onset and specimen collection was similar to those for whom illness onset date was documented to be ≤7 days before specimen collection, suggesting minimal outcome misclassification associated with information bias. The likelihood of influenza testing was similar between vaccinated and unvaccinated individuals, suggesting an absence of selection bias that could arise when a case definition for influenza testing is not employed. Lastly, VE estimates were similar under various conditions, demonstrating the robustness of using these data, and were comparable to published estimates. Conclusion/ImplicationsThe FOREVER Cohort can be used to estimate VE with negligible bias. Compared to traditional VE studies that are limited to recruited patients, routinely collected specimens create a larger, more generalizable sample. Linkage to health administrative databases can identify those with comorbidities and permit evaluation of VE in high-risk groups.

Automatic notification and infectious diseases consultation for patients with Staphylococcus aureus bacteremia

Observational studies suggest that Infectious Diseases (ID) consultation is associated with improved outcomes for patients with Staphylococcus aureus bacteremia (SAB), but few studies have sought to standardize timely ID consultation through automatic notification by the Microbiology laboratory. In this 3-year quasi-experimental evaluation, introduction of this change resulted in increased ID consultation for SAB (70% versus 100%, P < 0.001) and decreased time to consultation (14.5 versus 4 h, P < 0.0001). Adherence to Quality of Care Indicators (QCIs) increased (45% versus 87%, P < 0.0002), transfer to intensive care unit decreased (38% versus 16%, P = 0.03), while decrease in 30-day readmission or death did not reach statistical significance (33% versus 27%, P = 0.5). Automatic notification and ID consultation for patients with SAB are a feasible system for ensuring improved adherence to established QCIs.

Factors associated with influenza vaccination among healthcare workers in acute care hospitals in Canada

BACKGROUND

Influenza vaccine coverage rates among healthcare workers (HCWs) in acute care facilities in Canada remain below national targets.

OBJECTIVE

To determine factors associated with influenza vaccine uptake among HCWs.

METHODS

This secondary analysis of a prospective cohort study included HCWs aged 18-69 years, working ≥20 h/wk in a Canadian acute care hospital. Questionnaires were administered to participants in the fall of the season of participation (2011/12-2013/14) which captured demographic/household characteristics, medical histories, occupational, behavioural and risk factors for influenza. Generalized estimating equation logistic regression was used to determine factors associated with vaccine uptake in the season of participation.

RESULTS

The adjusted odds ratio for influenza vaccination in the current season was highest for those vaccinated in 3 of 3 previous seasons (OR 156; 95% CI 98, 248) followed by those vaccinated in 2 of 3 and 1 of 3 previous seasons when compared with those not vaccinated. Compared with nurses, physicians (OR 4.2; 95% CI 1.4, 13.2) and support services staff (OR 1.8; 95% CI 1.3, 2.4) had higher odds ratios for vaccine uptake. Conversely, HCWs identifying as Black had lower odds of uptake compared with those with European ancestry (OR 0.44, 95% CI 0.26-0.75) when adjusted for other factors in the model.

CONCLUSION

Healthcare workers differ in their annual uptake of influenza vaccine based on their past vaccination history, occupation and ethnicity. These findings indicate a need to determine whether there are other vaccine-hesitant groups within healthcare settings and learn which approaches are successful in increasing their uptake of influenza vaccines.

Acute Myocardial Infarction after Laboratory-Confirmed Influenza Infection

BACKGROUND

Acute myocardial infarction can be triggered by acute respiratory infections. Previous studies have suggested an association between influenza and acute myocardial infarction, but those studies used nonspecific measures of influenza infection or study designs that were susceptible to bias. We evaluated the association between laboratory-confirmed influenza infection and acute myocardial infarction.

METHODS

We used the self-controlled case-series design to evaluate the association between laboratory-confirmed influenza infection and hospitalization for acute myocardial infarction. We used various high-specificity laboratory methods to confirm influenza infection in respiratory specimens, and we ascertained hospitalization for acute myocardial infarction from administrative data. We defined the "risk interval" as the first 7 days after respiratory specimen collection and the "control interval" as 1 year before and 1 year after the risk interval.

RESULTS

We identified 364 hospitalizations for acute myocardial infarction that occurred within 1 year before and 1 year after a positive test result for influenza. Of these, 20 (20.0 admissions per week) occurred during the risk interval and 344 (3.3 admissions per week) occurred during the control interval. The incidence ratio of an admission for acute myocardial infarction during the risk interval as compared with the control interval was 6.05 (95% confidence interval [CI], 3.86 to 9.50). No increased incidence was observed after day 7. Incidence ratios for acute myocardial infarction within 7 days after detection of influenza B, influenza A, respiratory syncytial virus, and other viruses were 10.11 (95% CI, 4.37 to 23.38), 5.17 (95% CI, 3.02 to 8.84), 3.51 (95% CI, 1.11 to 11.12), and 2.77 (95% CI, 1.23 to 6.24), respectively.

CONCLUSIONS

We found a significant association between respiratory infections, especially influenza, and acute myocardial infarction. (Funded by the Canadian Institutes of Health Research and others.).

Elimination of Screening Urine Cultures Prior to Elective Joint Arthroplasty

Discontinuing routine processing of screening urine cultures prior to elective joint arthroplasty resulted in substantial reduction in urine cultures ordered and antimicrobial prescriptions for asymptomatic bacteriuria, without any significant impact on incidence of prosthetic joint infection. This simple change would be scalable across institutions with potential for significant healthcare savings.

Vaccine effectiveness against laboratory-confirmed influenza hospitalizations among young children during the 2010-11 to 2013-14 influenza seasons in Ontario, Canada

Uncertainty remains regarding the magnitude of effectiveness of influenza vaccines for preventing serious outcomes, especially among young children. We estimated vaccine effectiveness (VE) against laboratory-confirmed influenza hospitalizations among children aged 6-59 months. We used the test-negative design in hospitalized children in Ontario, Canada during the 2010-11 to 2013-14 influenza seasons. We used logistic regression models adjusted for age, season, and time within season to calculate VE estimates by vaccination status (full vs. partial), age group, and influenza season. We also assessed VE incorporating prior history of influenza vaccination. We included specimens from 9,982 patient hospitalization episodes over four seasons, with 12.8% testing positive for influenza. We observed variation in VE by vaccination status, age group, and influenza season. For the four seasons combined, VE was 60% (95%CI, 44%-72%) for full vaccination and 39% (95%CI, 17%-56%) for partial vaccination. VE for full vaccination was 67% (95%CI, 48%-79%) for children aged 24-59 months, 48% (95%CI, 12%-69%) for children aged 6-23 months, 77% (95%CI, 47%-90%) for 2010-11, 59% (95%CI, 13%-81%) for 2011-12, 33% (95%CI, -18% to 62%) for 2012-13, and 72% (95%CI, 42%-86%) for 2013-14. VE in children aged 24-59 months appeared similar between those vaccinated in both the current and previous seasons and those vaccinated in the current season only, with the exception of 2012-13, when VE was lower for those vaccinated in the current season only. Influenza vaccination is effective in preventing pediatric laboratory-confirmed influenza hospitalizations during most seasons.

Susceptibilities of clinical Clostridium difficile isolates to antimicrobials: a systematic review and meta-analysis of studies since 1970

OBJECTIVES

Although exposure to antibiotics can cause Clostridium difficile infection, certain antibiotics are used to treat C. difficile. Measurements of antimicrobial C. difficile activity could help to identify antibiotic risk and emergent resistance. Here, we describe publication patterns relating to C. difficile susceptibilities and estimate minimum inhibitory concentrations (MIC) for antibiotic classes in the published literature between January 1970 and June 2014.

METHODS

We queried PUBMED and EMBASE for studies reporting antibiotic C. difficile MIC in English or French. We used mixed-effects models to obtain pooled estimates of antibiotic class median MIC (MIC₅₀), 90th percentile of MIC (MIC₉₀), and MIC₉₀:MIC₅₀ ratio.

RESULTS

Our search identified 182 articles that met our inclusion criteria, of which 27 were retained for meta-analysis. Aminoglycosides (MIC₅₀ 120 mg/L, 95% CI 62-250), 3rd (MIC₅₀ 75 mg/L, 95% CI 39-130) and 2nd generation cephalosporins (MIC₅₀ 64 mg/L, 95% CI 27-140) had the least C. difficile activity. Rifamycins (MIC₅₀ 0.034 mg/L, 95% CI 0.012-0.099) and tetracyclines (MIC₅₀ 0.29 mg/L, 95% CI 0.054-1.7) had the highest level of activity. The activity of 3rd generation cephalosporins was more than three times lower than that of 1st generation agents (MIC₅₀ 19 mg/L, 95% CI 7.0-54). Time-trends in MIC₅₀ were increasing for carbapenems (70% increase per 10 years) while decreasing for tetracyclines (51% decrease per 10 years).

CONCLUSIONS

We found a 3500-fold variation in antibiotic C. difficile MIC₅₀, with aminoglycosides as the least active agents and rifamycins as the most active. Further research is needed to determine how in vitro measures can help assess patient C. difficile risk and guide antimicrobial stewardship.

A prospective study evaluating tobramycin pharmacokinetics and optimal once daily dosing in burn patients

BACKGROUND

Once-daily aminoglycoside dosing (ODA) is used in most patient populations to optimize antibacterial activity and reduce toxicity. Unfortunately, burn patients are excluded from ODA due to concerns over altered pharmacokinetics resulting in a shortened half-life and low peak aminoglycoside concentrations. Retrospective studies suggest that ODA may be appropriate if higher milligram/kilogram doses are used. However, no prospective clinical trials in burn patients exist to confirm these findings.

OBJECTIVE

To determine the adequacy of once daily tobramycin dosed at 10mg/kg in adult burn patients.

METHODS

This prospective single dose pharmacokinetic clinical trial was conducted at the Ross Tilley Burn Centre. Patients with a total burn surface area (TBSA) of <20% and creatinine clearance ≥50mL/min were eligible. A first-order one compartment model was used to determine the pharmacokinetic profile from 3 or 5 tobramycin levels over a 24h period per patient. Monte Carlo simulation (MCS) was performed to determine the probability of target level attainment.

RESULTS

The mean percent TBSA, partial, and full thickness burn were 10%, 6%, and 4%, respectively. Nine of the ten patients recruited achieved peak concentrations of ≥20mg/L (mean of 29.4±5.7mg/L) and all patients had a trough level ≤0.5mg/L. The mean half-life, volume of distribution, and clearance were 2.58h, 0.33L/kg, and 7.40L/h, respectively. The MCS determined probability of attaining target peak concentrations with the 10mg/kg dose was 97%, which almost doubled that predicted with the usual 7mg/kg dose.

CONCLUSION

Burn patients with adequate renal function and <20% TBSA are candidates for ODA. Tobramycin half-life was similar to healthy, non-burn patients. The larger than normal volume of distribution supports the use of the higher empiric dose of 10mg/kg total body or adjusted weight in non-obese and obese patients, respectively, with further dose adjustment based on therapeutic drug monitoring.

Pre-and post-pandemic trends in antiviral use in hospitalized patients with laboratory-confirmed influenza: 2004/05-2013/14, Toronto, Canada

BACKGROUND

Data on factors associated with the use of antiviral medication to treat influenza in both children and adults are limited.

OBJECTIVES

To describe trends in antiviral use, analyze factors associated with antiviral treatment of hospitalized patients with influenza, and to compare use based on guidelines.

STUDY DESIGN

A retrospective observational cohort of hospitalized patients with laboratory confirmed influenza in southern Ontario hospitals for the 2004/05-2013/14 seasons.

RESULTS

Of the 7967 patients, 18% of the 1779 children (<15 years) and 66% of the 6188 adults received antiviral therapy. The percentage treated increased from 29% pre-pandemic to 74% during the pandemic, decreased to 55% in 2011/12 and then increased to 65% in 2013/14. Factors significantly associated with antiviral prescription across all age groups during the non-pandemic seasons include influenza type, disease severity, interval between symptom onset and test sample submission, and clinician suspicion of influenza. Rate of treatment of patients meeting guideline criteria was low for children and moderate for adults.

CONCLUSIONS

Since the pandemic, there has been a sustained increase in the use of antiviral medication for all age groups of hospitalized patients with influenza, but much higher for adults than children. The odds of treatment are higher for patients with more severe disease as well as for those tested within 48 h of symptom onset, both of which are part of the guidelines for treatment with anti-influenza medications.

Modeling Transmission of Methicillin-ResistantStaphylococcus AureusAmong Patients Admitted to a Hospital

Objective:

To determine the impact of the screening test, nursing workload, handwashing rates, and dependence of handwashing on risk level of patient visit on methicillin-resistantStaphylococcus aureus(MRSA) transmission among hospitalized patients.

Setting:

General medical ward.

Methods:

Monte Carlo simulation was used to model MRSA transmission (median rate per 1,000 patient-days). Visits by healthcare workers (HCWs) to patients were simulated, and MRSA was assumed to be transmitted among patients via HCWs.

Results:

The transmission rate was reduced from 0.89 to 0.56 by the combination of increasing the sensitivity of the screening test from 80% to 99% and being able to report results in 1 day instead of 4 days. Reducing the patient-to-nurse ratio from 4.3 in the day and 6.8 at night to 3.8 and 5.7, respectively, reduced the number of nosocomial infections from 0.89 to 0.85; reducing the ratio to 1 and 1, respectively, further reduced the number of nosocomial infections to 0.32. Increases in handwashing rates by 0%, 10%, and 20% for high-risk visits yielded reductions in nosocomial infections similar to those yielded by increases in handwashing rates for all visits (0.89, 0.36, and 0.24, respectively). Screening all patients for MRSA at admission reduced the transmission rate to 0.81 per 1,000 patient-days from 1.37 if no patients were screened.

Conclusion:

Within the ranges of parameters studied, the most effective strategies for reducing the rate of MRSA transmission were increasing the handwashing rates for visits involving contact with skin or bodily fluid and screening patients for MRSA at admission. (Infect Control Hosp Epidemiol 2005;26:607- 615)

Antibiotic Use and Need for Antimicrobial Stewardship in Long-Term Care

BACKGROUND

Antimicrobial stewardship may be important in long-term care facilities because of unnecessary or inappropriate antibiotic use observed in these residents, coupled with their increased vulnerability to health care-associated infections.

OBJECTIVES

To assess antibiotic use in a long-term care facility in order to identify potential antimicrobial stewardship needs.

METHODS

A retrospective descriptive study was conducted at the Veterans Centre, a long-term care facility at Sunnybrook Health Sciences Centre, Toronto, Ontario. All residents taking one or more antibiotics (n = 326) were included as participants. Antibiotic-use data for patients residing in the facility between April 1, 2011, and March 31, 2012, were collected and analyzed.

RESULTS

Totals of 358 patient encounters, 835 antibiotic prescriptions, and 193 positive culture results were documented during the study period. For 36% (302/835) of antibiotic prescriptions, the duration was more than 7 days. Cephalosporins (30%; 251/835) and fluoroquinolones (28%; 235/835) were the most frequently prescribed antibiotic classes. Urine was the most common source of samples for culture (60%; 116/193).

CONCLUSIONS

Characteristics of antimicrobial use at this long-term care facility that might benefit from further evaluation included potentially excessive use of fluoroquinolones and cephalosporins and potentially excessive duration of antibiotic use for individual patients.

Impact of hospital length of stay on the distribution of Gram negative bacteria and likelihood of isolating a resistant organism in a Canadian burn center

RATIONALE

The impact of hospital length of stay (LOS) on the distribution and susceptibility of Gram negative bacteria (GNB) causing infection in burn patients remains unexplored. Knowledge of causative pathogens is important in guiding empiric antibiotic therapy.

OBJECTIVES

To characterize the distribution of GNB causing infection and to identify changes in susceptibility with LOS in a tertiary care burn center.

METHODS

A retrospective review of all admissions to the Ross Tilley Burn Centre at Sunnybrook Health Sciences Centre with clinical cultures yielding GNB (duplicates excluded) between March 12, 2010 to July 17, 2013 was completed. Positive cultures were categorized into 5 clinically relevant time periods (in days) based on specimen collection date relative to the patient's date of admission: 0-7, 7-14, 14-21, 21-28, >28. Chi-square for proportions was used to compare the time periods.

RESULTS

The proportion of patients with clinical cultures for P. aeruginosa increased with hospital LOS (0-7 days: 8% vs. >28 days: 55%; p<0.05). Conversely, clinical cultures for H. influenzae occurred primarily within the first 7 days of hospitalization (0-7 days: 36% vs. >28 days: 0.7%; p<0.05). Enterobacteriaceae isolation was highest between 7 and 14 days of hospitalization (7-14 days: 62% vs. >28 days: 38%; p<0.05). Antibiotic resistance was directly proportional to hospital LOS (% patients with multidrug resistant GNB increased from 6% [LOS 0-7 days] to 44% [LOS>28 days]; p<0.05).

CONCLUSIONS

This study provides objective data documenting changes in species and resistance patterns of GNB causing infection in patients admitted to a burn center as a function of hospital LOS; which may support delaying the use of broad spectrum antibiotics (e.g. carbapenems and beta-lactam/beta-lactamase inhibitors) in clinically stable patients.

Impact of infection with extended-spectrum β-lactamase-producing Escherichia coli or Klebsiella species on outcome and hospitalization costs

BACKGROUND

Extended-spectrum β-lactamase (ESBL)-producing bacteria are important sources of infection; however, Canadian data evaluating the impact of ESBL-associated infection are lacking.

AIM

To determine whether patients infected with ESBL-producing Escherichia coli or Klebsiella species (ESBL-EcKs) exhibit differences in clinical outcome, microbiological outcome, mortality, and/or hospital resource use compared to patients infected with non-ESBL-producing strains.

METHODS

A retrospective case-control study of 75 case patients with ESBL-EcKs matched to controls infected with non-ESBL-EcKs who were hospitalized from June 2010 to April 2013 was conducted. Patient-level cost data were provided by the institution's business office. Clinical data were collected using the electronic databases and paper charts.

FINDINGS

Median infection-related hospitalization costs per patient were greater for cases than controls (C$10,507 vs C$7,882; median difference: C$3,416; P = 0.04). The primary driver of increased costs was prolonged infection-related hospital length of stay (8 vs 6 days; P = 0.02) with patient location (ward, ICU) and indirect care costs (including costs associated with infection prevention and control) as the leading cost categories. Cases were more likely to experience clinical failure (25% vs 11%; P = 0.03), with a higher all-cause mortality (17% vs 5%; P = 0.04). Less than half of case patients were prescribed appropriate empiric antimicrobial therapy, whereas controls received adequate initial treatment in nearly all circumstances (48% vs 96%; P < 0.01).

CONCLUSION

Patients with infection caused by ESBL-EcKs are at increased risk for clinical failure and mortality, with additional cost to the Canadian healthcare system of C$3,416 per patient.

Outcomes in Documented Pseudomonas aeruginosa Bacteremia Treated with Intermittent IV Infusion of Ceftazidime, Meropenem, or Piperacillin-Tazobactam: A Retrospective Study

BACKGROUND

Pseudomonas aeruginosa, one of the leading causes of nosocomial gram-negative bloodstream infections, is particularly difficult to treat because of its multiple resistance mechanisms combined with a lack of novel antipseudomonal antibiotics. Despite knowledge of time-dependent killing with ß-lactam antibiotics, most hospitals in Canada currently administer ß-lactam antibiotics by intermittent rather than extended infusions.

OBJECTIVES

To determine clinical outcomes, microbiological outcomes, total hospital costs, and infection-related costs for patients with P. aeruginosa bacteremia who received intermittent IV administration of antipseudomonal ß-lactam antibiotics in a tertiary care institution.

METHODS

For this retrospective descriptive study, data were collected for patients who were admitted between March 1, 2005, and March 31, 2013, who had P. aeruginosa bacteremia during their admission, and who received at least 72 h of treatment with ceftazidime, meropenem, or piperacillin-tazobactam. Clinical and microbiological outcomes were determined, and total and infection-related hospital costs were calculated.

RESULTS

A total of 103 patients were included in the analysis, of whom 79 (77%) experienced clinical cure. In addition, bacterial eradication was achieved in 41 (87%) of the 47 patients with evaluable data for this outcome. Twenty-eight (27%) of the 103 patients died within 30 days of discontinuation of antipseudomonal ß-lactam antibiotic therapy. The median total cost of the hospital stay was $121 718, and the median infection-related cost was $29 697.

CONCLUSIONS

P. aeruginosa bacteremia is a clinically significant nosocomial infection that continues to cause considerable mortality and health care costs. To the authors' knowledge, no previous studies have calculated total and infection-related hospital costs for treatment of P. aeruginosa bacteremia with intermittent infusion of antipseudomonal ß-lactam antibiotics, with characterization of cost according to site of acquisition of the infection. This study may provide important baseline data for assessing the impact of implementing extended-infusion ß-lactam therapy, antimicrobial stewardship, and infection control strategies targeting P. aeruginosa infection in hospitalized patients.

Hospital ward antibiotic prescribing and the risks of Clostridium difficile infection

IMPORTANCE

Only a portion of hospital-acquired Clostridium difficile infections can be traced back to source patients identified as having symptomatic disease. Antibiotic exposure is the main risk factor for C difficile infection for individual patients and is also associated with increased asymptomatic shedding. Contact with patients taking antibiotics within the same hospital ward may be a transmission risk factor for C difficile infection, but this hypothesis has never been tested.

OBJECTIVES

To obtain a complete portrait of inpatient risk that incorporates innate patient risk factors and transmission risk factors measured at the hospital ward level and to investigate ward-level rates of antibiotic use and C difficile infection risk.

DESIGN, SETTING, AND PATIENTS

A 46-month (June 1, 2010, through March 31, 2014) retrospective cohort study of inpatients 18 years or older in a large, acute care teaching hospital composed of 16 wards, including 5 intensive care units and 11 non-intensive care unit wards.

EXPOSURES

Patient-level risk factors (eg, age, comorbidities, hospitalization history, antibiotic exposure) and ward-level risk factors (eg, antibiotic therapy per 100 patient-days, hand hygiene adherence, mean patient age) were identified from hospital databases.

MAIN OUTCOMES AND MEASURES

Incidence of hospital-acquired C difficile infection as identified prospectively by hospital infection prevention and control staff.

RESULTS

A total of 255 of 34 298 patients developed C difficile (incidence rate, 5.95 per 10,000 patient-days; 95% CI, 5.26-6.73). Ward-level antibiotic exposure varied from 21.7 to 56.4 days of therapy per 100 patient-days. Each 10% increase in ward-level antibiotic exposure was associated with a 2.1 per 10,000 (P < .001) increase in C difficile incidence. The association between C difficile incidence and ward antibiotic exposure was the same among patients with and without recent antibiotic exposure, and C difficile risk persisted after multilevel, multivariate adjustment for differences in patient-risk factors among wards (relative risk, 1.34 per 10% increase in days of therapy; 95% CI, 1.16-1.57).

CONCLUSIONS AND RELEVANCE

Among hospital inpatients, ward-level antibiotic prescribing is associated with a statistically significant and clinically relevant increase in C difficile risk that persists after adjustment for differences in patient-level antibiotic use and other patient- and ward-level risk factors. These data strongly support the use of antibiotic stewardship as a means of preventing C difficile infection.

Facility-Level Correlates of Antimicrobial Use in Nursing Homes

We assessed the contribution of facility-Ievel variables to antimicrobial use in a cohort of 50 nursing homes and found that antimicrobial use was significantly correlated with the percentage of nursing home residents with feeding tubes, the number of healthcare aides, and the country of origin of the facility.

Complete Sequence of Four Multidrug-Resistant MOBQ1 Plasmids Harboring blaGES-5 Isolated from Escherichia coli and Serratia marcescens Persisting in a Hospital in Canada

The usefulness of carbapenems for gram-negative infections is becoming compromised by organisms harboring carbapenemases, enzymes which can hydrolyze the drug. Currently KPC (class A), NDM (class B), and OXA-48 types (class D) are the most globally widespread carbapenemases. However, among the GES-type class A extended-spectrum β-lactamases (ESBLs) there are variants that hydrolyze carbapenems, with blaGES-5 being the most common. Two Escherichia coli and two Serratia marcescens harboring blaGES-5 on plasmids were isolated by the Canadian Nosocomial Infection Surveillance Program (CNISP) from four different patients in a single hospital over a 2-year period. Complete sequencing of the blaGES-5 plasmids indicated that all four had nearly identical backbones consisting of genes for replication, partitioning, and stability, but contained variant accessory regions consisting of mobile elements and antimicrobial resistance genes. The plasmids were of a novel replicon type, but belonged to the MOBQ1 group based on relaxase sequences, and appeared to be mobilizable, but not self-transmissible. Considering the time periods of bacterial isolation, it would appear the blaGES-5 plasmid has persisted in an environmental niche for at least 2 years in the hospital. This has implications for infection control and clinical care when it is transferred to clinically relevant gram-negative organisms.

Point prevalence survey of antimicrobial utilization in a Canadian tertiary-care teaching hospital

Objectives: Inappropriate antimicrobial use can promote antimicrobial resistance, which is associated with increased patient morbidity and mortality. Identifying the pattern of antimicrobial use can provide data from which targeted antimicrobial stewardship interventions can be made. The primary objective was to identify the prevalence of antimicrobial use at a tertiary care teaching hospital with both acute and long-term care patients.

Methods: A point prevalence study was conducted on July 19th, 2012. Data on antimicrobial utilization, indication for prescribing, duration of therapy, and frequency of infectious disease or antimicrobial stewardship consultations were collected using a customized integrated stewardship database (SPIRIT) and prospective chart review.

Results: One or more antimicrobial agents were ordered in 31% and 4% of acute care and long-term care patients, respectively. Respiratory and urinary tract infections were the most common indication for antimicrobial therapy in both acute and long-term care. About 25% of surgical prophylaxis orders were prescribed for greater than 24 h.

Conclusion: This prospective point prevalence survey provided important baseline information on antimicrobial use within a large tertiary care teaching hospital and identified potential targets for future antimicrobial stewardship initiatives. A multi-center point prevalence survey should be considered to identify patterns of antimicrobial use in Canada and to establish the first steps toward international antimicrobial surveillance.

Modeling the economic impact of linezolid versus vancomycin in confirmed nosocomial pneumonia caused by methicillin-resistant Staphylococcus aureus

Introduction

We compared the economic impacts of linezolid and vancomycin for the treatment of hospitalized patients with methicillin-resistant Staphylococcus aureus (MRSA)–confirmed nosocomial pneumonia.

Methods

We used a 4-week decision tree model incorporating published data and expert opinion on clinical parameters, resource use and costs (in 2012 US dollars), such as efficacy, mortality, serious adverse events, treatment duration and length of hospital stay. The results presented are from a US payer perspective. The base case first-line treatment duration for patients with MRSA-confirmed nosocomial pneumonia was 10 days. Clinical treatment success (used for the cost-effectiveness ratio) and failure due to lack of efficacy, serious adverse events or mortality were possible clinical outcomes that could impact costs. Cost of treatment and incremental cost-effectiveness per successfully treated patient were calculated for linezolid versus vancomycin. Univariate (one-way) and probabilistic sensitivity analyses were conducted.

Results

The model allowed us to calculate the total base case inpatient costs as $46,168 (linezolid) and $46,992 (vancomycin). The incremental cost-effectiveness ratio favored linezolid (versus vancomycin), with lower costs ($824 less) and greater efficacy (+2.7% absolute difference in the proportion of patients successfully treated for MRSA nosocomial pneumonia). Approximately 80% of the total treatment costs were attributed to hospital stay (primarily in the intensive care unit). The results of our probabilistic sensitivity analysis indicated that linezolid is the cost-effective alternative under varying willingness to pay thresholds.

Conclusion

These model results show that linezolid has a favorable incremental cost-effectiveness ratio compared to vancomycin for MRSA-confirmed nosocomial pneumonia, largely attributable to the higher clinical trial response rate of patients treated with linezolid. The higher drug acquisition cost of linezolid was offset by lower treatment failure–related costs and fewer days of hospitalization.

Hospital-wide rollout of antimicrobial stewardship: a stepped-wedge randomized trial

Our objective was to rigorously evaluate the impact of an antimicrobial stewardship audit-and-feedback intervention, via a stepped-wedge randomized trial. An effective intensive care unit (ICU) audit-and-feedback program was rolled out to 6 non-ICU services in a randomized sequence. The primary outcome was targeted antimicrobial utilization, using a negative binomial regression model to assess the impact of the intervention while accounting for secular and seasonal trends. The intervention was successfully transitioned, with high volumes of orders reviewed, suggestions made, and recommendations accepted. Among patients meeting stewardship review criteria, the intervention was associated with a large reduction in targeted antimicrobial utilization (-21%, P = .004); however, there was no significant change in targeted antibiotic use among all admitted patients (-1.2%, P = .9), and no reductions in overall costs and microbiologic outcomes. An ICU day 3 audit-and-feedback program can be successfully expanded hospital-wide, but broader benefits on non-ICU wards may require interventions earlier in the course of treatment.

Determination of vancomycin pharmacokinetics in neonates to develop practical initial dosing recommendations

Variability in neonatal vancomycin pharmacokinetics and the lack of consensus for optimal trough concentrations in neonatal intensive care units pose challenges to dosing vancomycin in neonates. Our objective was to determine vancomycin pharmacokinetics in neonates and evaluate dosing regimens to identify whether practical initial recommendations that targeted trough concentrations most commonly used in neonatal intensive care units could be determined. Fifty neonates who received vancomycin with at least one set of steady-state levels were evaluated retrospectively. Mean pharmacokinetic values were determined using first-order pharmacokinetic equations, and Monte Carlo simulation was used to evaluate initial dosing recommendations for target trough concentrations of 15 to 20 mg/liter, 5 to 20 mg/liter, and ≤20 mg/liter. Monte Carlo simulation revealed that dosing by mg/kg of body weight was optimal where intermittent dosing of 9 to 12 mg/kg intravenously (i.v.) every 8 h (q8h) had the highest probability of attaining a target trough concentration of 15 to 20 mg/liter. However, continuous infusion with a loading dose of 10 mg/kg followed by 25 to 30 mg/kg per day infused over 24 h had the best overall probability of target attainment. Initial intermittent dosing of 9 to 15 mg/kg i.v. q12h was optimal for target trough concentrations of 5 to 20 mg/liter and ≤20 mg/liter. In conclusion, we determined that the practical initial vancomycin dose of 10 mg/kg vancomycin i.v. q12h was optimal for vancomycin trough concentrations of either 5 to 20 mg/liter or ≤20 mg/liter and that the same initial dose q8h was optimal for target trough concentrations of 15 to 20 mg/liter. However, due to large interpatient vancomycin pharmacokinetic variability in neonates, monitoring of serum concentrations is recommended when trough concentrations between 15 and 20 mg/liter or 5 and 20 mg/liter are desired.

Cost-effectiveness and efficacy of spa, SCCmec, and PVL genotyping of methicillin-resistant Staphylococcus aureus as compared to pulsed-field gel Electrophoresis

Pulsed-field gel electrophoresis (PFGE) is a valuable molecular typing assay used for methicillin-resistant Staphylococcus aureus (MRSA) surveillance and genotyping. However, there are several limitations associated with PFGE. In Alberta, Canada, the significant increase in the number of MRSA isolates submitted to the Provincial Laboratory for Public Health (ProvLab) for PFGE typing led to the need for an alternative genotyping method. In this study, we describe the transition from PFGE to Staphylococcus protein A (spa), Staphylococcal cassette chromosome (SCCmec), and Panton-Valentine leukocidin (PVL) typing. A total of 1915 clinical MRSA isolates collected from 2005 to 2009 were used to develop and validate an algorithm for assigning PFGE epidemic types using spa, SCCmec, and PVL typing and the resulting data was used to populate a new Alberta MRSA typing database. An additional 12620 clinical MRSA isolates collected from 2010 to 2012 as part of ongoing routine molecular testing at ProvLab were characterized using the new typing algorithm and the Alberta MRSA typing database. Switching to spa, SCCmec, and PVL from PFGE typing substantially reduced hands-on and turn-around times while maintaining historical PFGE epidemic type designations. This led to an approximate $77,000 reduction in costs from 2010 to 2012. PFGE typing is still required for a small subset of MRSA isolates that have spa types that are rare, novel, or associated with more than one PFGE epidemic type.

Risk factors for influenza among health care workers during 2009 pandemic, Toronto, Ontario, Canada

Influenza was associated with household exposure, aerosol-generating procedures, and lower adherence to hand hygiene recommendations.

Co-circulation of multiple genotypes of human rhinovirus during a large outbreak of respiratory illness in a veterans' long-term care home

Background

Human rhinoviruses (HRVs) are a well-recognized cause of long-term care home (LTCH) outbreaks of respiratory illness. However, there are limited data on the molecular epidemiology of the HRV types involved.

Objectives

To determine whether a large respiratory outbreak in a LTCH was caused by a single type of HRV, and to describe the clinical impact of the outbreak.

Study design

Nasopharyngeal swabs were collected from residents with one or more of the following: fever, cough, rhinitis, or congestion. Specimens were interrogated by multiplex PCR using the ResPlex II assay. Samples positive for HRV were then submitted for genotyping by partial sequence analysis of the 5′ untranslated (UTR) and viral protein (VP) 1 capsid regions.

Results

Of 71 screened, 56 residents were positive for a HRV during an outbreak that lasted 5.5 weeks; 27 healthcare workers also had respiratory symptoms. Three residents were transferred to hospital and 2 died. Seven units in two wings of the LTCH were affected, resulting in 3152.5 resident unit closure days. Three different HRV genotypes were identified, although HRV-A1 dominated.

Conclusions

This large outbreak of HRVs among residents and healthcare workers in a LTCH was associated with substantial resident and staff morbidity as well as significant unit closures. Multiple types of HRV were implicated but an HRV-A1 type dominated, warranting further investigation into viral determinants for virulence and transmission.

Antibiotic resistance of ocular surface flora with repeated use of a topical antibiotic after intravitreal injection

IMPORTANCE

Treatment with intravitreal (IVT) injections has increased during the last several years as evidence has accumulated demonstrating the efficacy of anti-vascular endothelial growth factor agents in the treatment of neovascular age-related macular degeneration (AMD) and various retinal vascular diseases. Although IVT injections are generally safe, infectious endophthalmitis is a rare but devastating complication, and the risk of morbidity and vision loss from endophthalmitis is high.

OBJECTIVE

To examine the change in antibiotic resistance of ocular surface flora with repeated prophylactic use of antibiotics after IVT injection for AMD.

DESIGN AND SETTING

Prospective, nonrandomized cohort study in 2 tertiary academic hospitals.

PARTICIPANTS

Patients 65 years and older with newly diagnosed AMD were recruited by 7 retinal specialists from July 1, 2010, through December 31, 2011.

INTERVENTION

The study group received topical moxifloxacin hydrochloride for 3 days after each monthly IVT injection.

MAIN OUTCOME MEASURE

Resistance to moxifloxacin and ceftazidime in cultured isolates at baseline and monthly for 3 months by change in minimal inhibitory concentration (MIC) of culture isolates was studied.

RESULTS

The study group consisted of 84 patients, and the control group had 94 patients. In the study group, the baseline adjusted MIC increased (from 1.04 to 1.25 μg/mL; P = .01) as did the MIC for 50% of isolates (MIC50) (from 0.64 to 1.00 μg/mL) and the MIC for 90% of isolates (MIC90) (from 0.94 to 4.00 μg/mL). In both groups, the culture-positive rate did not change significantly when adjusted for baseline. No significant change was found in the MIC level, culture-positive rate, MIC50 level, and MIC90 level in the control group. Subgroup analysis found diabetes mellitus to be noncontributory to both the MIC and culture-positive rate. No endophthalmitis or adverse events were reported.

CONCLUSIONS AND RELEVANCE

Repeated use of topical moxifloxacin after IVT injection significantly increases antibiotic resistance of ocular surface flora. We recommend that routine use of prophylactic antibiotics after IVT injection be discouraged. TRIAL REGISTRATION clinicaltrials.gov Identifier: NCT01181713.