Objectives: International infectious disease/obstetrical societies have recently recommended universal hepatitis C virus (HCV) prenatal screening and these same recommendations are forthcoming in Canada. At present, there is no formal analysis of universal HCV screening or linkage to care of pregnant people in Ontario. The objectives of our study were to determine the seroprevalence of HCV using 2 different methods to evaluate universal screening, as well as identify opportunities that may improve linkage to care. Methods: To assess seroprevalence in a large urban area, we aimed to test 12 000 de -identified samples submitted for prenatal HIV testing in the catchment area of Toronto Public Health for HCV antibodies. Then, to assess the seroprevalence as well as the operational impact and follow-up in a real -world setting, we completed a Quality Improvement Project (QIP) for 1 year at a large tertiary care obstetrical centre in London, Ontario. Results: From 2019 to 2021, 11 999 de-identified samples were screened from Toronto with a seroprevalence of 0.40 (95% CI 0.29-0.53). In London, 5771 people were screened in 2021 with seroprevalence of 0.55% (95% CI 0.38-0.78). Taken together, those aged 26-35 years had the highest positivity; in the QIP, had no documented risk factor, and 59% of individuals were not linked to the next step in HCV care. Conclusions: HCV prenatal seroprevalence in Ontario is comparable to hepatitis B virus, and w15-30-fold higher than HIV. Diagnosis pregnancy is critical to facilitate referrals for treatment between pregnancies and could increase screening among children born positive women.

Background:In response to the COVID-19 pandemic, a new oral antiviral called nirmatrelvir-ritonavir (PaxlovidTM) was authorized for use in Canada in January 2022. In vitro studies have reported mutations in Mpro protein that may be associated with the development of nirmatrelvir resistance. Objectives:To survey the prevalence, relevance and temporal patterns of Mpro mutations among SARS-CoV-2 Omicron lineages in Ontario, Canada. Methods:A total of 93,082 Mpro gene sequences from December 2021 to September 2023 were analyzed. Reported in vitro Mpro mutations were screened against our database using in-house data science pipelines to determine the nirmatrelvir resistance. Negative binomial regression was conducted to analyze the temporal trends in Mpro mutation counts over the study time period. Results:A declining trend was observed in non-synonymous mutations of Mpro sequences, showing a 7.9% reduction (95% CI: 6.5%-‬9.4%; p<0.001) every 30 days. The P132H was the most prevalent mutation (higher than 95%) in all Omicron lineages. In vitro nirmatrelvir-resistant mutations were found in 3.12% (n=29/929) Omicron lineages with very low counts, ranging from one to 19. Only two mutations, A7T (n=19) and M82I (n=9), showed temporal presence among the BA.1.1 in 2022 and the BQ.1.2.3 in 2022, respectively. Conclusion:The observations suggest that, as of September 2023, no significant or widespread resistance to nirmatrelvir has developed among SARS-CoV-2 Omicron variants in Ontario. This study highlights the importance of creating automated monitoring systems to track the emergence of nirmatrelvir-resistant mutations within the SARS-CoV-2 virus, utilizing genomic data generated in real-time.

Background: With the growing volume and complexity of laboratory repositories, it has become tedious to parse unstructured data into structured and tabulated formats for secondary uses such as decision support, quality assurance, and outcome analysis. However, advances in natural language processing (NLP) approaches have enabled efficient and automated extraction of clinically meaningful medical concepts from unstructured reports. Objective: In this study, we aimed to determine the feasibility of using the NLP model for information extraction as an alternative approach to a time-consuming and operationally resource-intensive handcrafted rule-based tool. Therefore, we sought to develop and evaluate a deep learning-based NLP model to derive knowledge and extract information from text-based laboratory reports sourced from a provincial laboratory repository system. Methods: The NLP model, a hierarchical multilabel classifier, was trained on a corpus of laboratory reports covering testing for 14 different respiratory viruses and viral subtypes. The corpus includes 87,500 unique laboratory reports annotated by 8 subject matter experts (SMEs). The classification task involved assigning the laboratory reports to labels at 2 levels: 24 fine-grained labels in level 1and 6 coarse-grained labels in level 2. A "label" also refers to the status of a specific virus or strain being tested or detected (eg, influenza A is detected). The model's performance stability and variation were analyzed across all labels in the classification task. Additionally, the model's generalizability was evaluated internally and externally on various test sets. Results: Overall, the NLP model performed well on internal, out-of-time (pre-COVID-19), and external (different laboratories) test sets with microaveraged F-1-scores >94% across all classes. Higher precision and recall scores with less variability were observed for the internal and pre-COVID-19 test sets. As expected, the model's performance varied across categories and virus types due to the imbalanced nature of the corpus and sample sizes per class. There were intrinsically fewer classes of viruses being detected than those tested; therefore, the model's performance (lowest F-1-score of 57%) was noticeably lower in the detected cases. Conclusions: We demonstrated that deep learning-based NLP models are promising solutions for information extraction from text-based laboratory reports. These approaches enable scalable, timely, and practical access to high-quality and encoded laboratory data if integrated into laboratory information system repositories.

Bloodstream infections (BSIs) represent a substantial mortality risk, yet most studies are limited to select pathogens or populations. The aim of this study was to describe the population-wide prevalence of BSIs and examine the associated mortality risk for the responsible microorganisms. Bloodstream infections (BSIs) represent a substantial mortality risk, yet most studies are limited to select pathogens or populations. The aim of this study was to describe the population-wide prevalence of BSIs and examine the associated mortality risk for the responsible microorganisms. We conducted a population-wide retrospective cohort study of BSIs in Ontario in 2017. Blood culture data was collected from almost all microbiology laboratories in Ontario and linked to data sets of patient characteristics. For each organism, we determined the prevalence and crude mortality risk, and using logistic regression models, the adjusted odds of 30-day mortality was calculated relative to patients with negative blood cultures and matched patients without blood culture testing. From 531,065 blood cultures, we identified 22,935 positive BSI episodes in 19,326 patients, for an incidence of 150 per 100,000 population. The most frequently isolated organisms were Escherichia coli, Staphylococcus aureus, coagulase-negative staphylococci, Klebsiella species, and Enterococcus species with 40.2, 22.4, 12.1, 11.1, and 7.1 episodes per 100,000 population respectively. BSI episodes were associated with 17.0% mortality at 30 days. Compared to patients with negative cultures, the adjusted 30-day mortality risk for positive BSIs was 1.47 (95% confidence interval (CI), 1.41 to 1.54) and compared to matched patients without blood culture testing was 2.62 (95% CI, 2.52 to 2.73). Clostridium species were associated with the highest adjusted odds of mortality compared to that of negative cultures (adjusted odds ratio, 5.81; 95% CI, 4.00 to 8.44). Among high incidence pathogens, Staphylococcus aureus had the highest odds ratio of mortality (adjusted odds ratio, 2.14; 95% CI, 1.94 to 2.36). BSIs are associated with increased mortality risk, varying across organisms.

Wildlife reservoirs of SARS-CoV-2 may enable viral adaptation and spillback from animals to humans. In North America, there is evidence of unsustained spillover of SARS-CoV-2 from humans to white-tailed deer ( Odocoileus virginianus ), but no evidence of transmission from deer to humans. Through a biosurveillance program in Ontario, Canada we identified a new and highly divergent lineage of SARS-CoV-2 in white-tailed deer. This lineage is the most divergent SARS-CoV-2 lineage identified to date, with 76 consensus mutations (including 37 previously associated with non-human animal hosts) and signatures of considerable evolution and transmission within wildlife. Phylogenetic analysis also revealed an epidemiologically linked human case. Together, our findings represent the first clear evidence of sustained evolution of SARS-CoV-2 in white-tailed deer and of deer-to-human transmission.

Wildlife reservoirs of broad-host-range viruses have the potential to enable evolution of viral variants that can emerge to infect humans. In North America, there is phylogenomic evidence of continual transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) from humans to white-tailed deer ( Odocoileus virginianus ) through unknown means, but no evidence of transmission from deer to humans. We carried out an observational surveillance study in Ontario, Canada during November and December 2021 ( n = 300 deer) and identified a highly divergent lineage of SARS-CoV-2 in white-tailed deer (B.1.641). This lineage is one of the most divergent SARS-CoV-2 lineages identified so far, with 76 mutations (including 37 previously associated with non-human mammalian hosts). From a set of five complete and two partial deer-derived viral genomes we applied phylogenomic, recombination, selection and mutation spectrum analyses, which provided evidence for evolution and transmission in deer and a shared ancestry with mink-derived virus. Our analysis also revealed an epidemiologically linked human infection. Taken together, our findings provide evidence for sustained evolution of SARS-CoV-2 in white-tailed deer and of deer-to-human transmission.

Background: Surveillance of antimicrobial resistance is essential to mitigate its impact on population health and inform local empiric treatment practices. Our aims were to evaluate urine culture specimen susceptibility from a range of diverse settings and describe antibiotic susceptibility across all organisms and compare susceptibilities to that of Escherichia coli alone. Methods: In this descriptive cohort study, we measured the prevalence of organisms in urine culture specimens using linked province-wide administrative databases. Using positive urine cultures collected in Ontario between Jan. 1, 2016, and Dec. 31, 2017, we measured susceptibility to 6 classes of antibiotics using a weighted antibiogram for all organisms compared with E. coli alone. Results: We included 689 497 cultures derived from 569 399 patients and 879 778 test orders for specimens. For all organisms, the rates of susceptibility in the outpatient, inpatient and long-term care settings were 49.3%, 42.8% and 39.2%, respectively, for ampicillin; 83.1%, 72.7% and 69.7%, respectively, for nitrofurantoin; 80.3%, 64.8% and 73.1%, respectively, for trimethoprim–sulfamethoxazole; 87.2%, 74.1% and 66.2%, respectively, for ciprofloxacin; 90.6%, 73.6% and 85.1%, respectively, for aminoglycosides; and 82.6%, 57.5% and 73.5%, respectively, for cefazolin. We found resistance to 3 or more antibiotic classes in 20.6% of episodes for all organisms compared with 14.0% for E. coli alone. The average absolute difference in antibiotic susceptibility between all organisms and E. coli across all drugs was lowest in the outpatient setting (6.2%) and highest in the inpatient setting (14.6%). Interpretation: In this study, urinary organism prevalence and antimicrobial susceptibility varied across health care settings and patient populations, with implications for both antimicrobial resistance surveillance and clinical decision-making. Weighted antibiograms may be most useful for guiding empiric treatment of urinary infections in inpatient settings where the diversity of infectious organisms is higher than in the community.

Abstract Background: For women aged 40-49, Canadian guidelines recommend individualized-decision making (based on risk assessment, values, and preferences) rather than routine screening mammography (SM). In this age group, family physicians are the gatekeepers to access SM; however, studies indicate substantial variability in practice patterns. There are few population-based data regarding uptake and patient/provider determinants of SM in this age group. We describe the uptake and frequency of SM and identify patient and provider level associations with SM in Ontario women aged 40-49. We hypothesized that SM would vary by provider characteristics and women’s demographics, suggesting lack of guideline-concordant care. Methods: This population-based retrospective cohort study linked health administrative databases to form a cohort of all Ontario women aged 40-49 between April 1, 2009 to March 31, 2019. Mammograms were identified using Ontario Health Billing codes. In order to identify mammograms that were specifically for screening, women were excluded if they had any prior breast MRI, mammogram, cancer diagnosis, oncologist visit, or breast surgical procedure. Sub-cohorts were created to identify women who had (a) at least one SM (“screen cohort”) and (b) 3 or more SM (“routine screen cohort”). Following SM, women were censored from cohorts if they had any cancer diagnosis, breast surgical procedure, oncologist visit, or death; however, breast cancer related outcomes were tracked for 6 months following SM, regardless of whether a censoring event occurred. Patient and provider characteristics were extracted for women in each cohort. A multivariable regression model was used to identify predictors of routine SM. Results: Of 2 million eligible women, 743 274 (35.6%) received a mammogram, 532 782 (25.5%) received at least one SM, and 90 651 (4.3%) received routine SM (3 or more). Table 1 demonstrates cohort characteristics. There were 0.32 and 0.52 mammograms per woman per year in the screen and routine screen cohort respectively. Call-backs were similar for women after the first SM compared to the third SM (9.5% vs 9.3%); however, there were more biopsies (3.2% vs 1.8%) and breast cancers diagnosed (1.2% vs 0.45%) within six months of the first SM. Compared to the full cohort, women in the routine screen cohort were more likely to have a family physician at cohort entry, be in higher-income quintiles, receive annual health exams, and receive have pap smears (p<0.001). Women in the screen cohort were more likely to have female providers and providers that were primarily paid fee for service versus capitation (p<0.001). Multivariable analysis will be reported at the meeting. Conclusions: Less than 5% of Ontario women 40-49 undergo routine SM. SM is associated with patient demographics related to higher socioeconomic status which could be related to higher risk of breast cancer and/or increased access to care. SM is also associated with some provider demographics which could be independent of breast cancer risk, suggesting lack of individualized risk assessment. Qualitative work is ongoing to explore this hypothesis. This information can inform guideline implementation strategies. Table 1: Patient and Provider Characteristics of ScreeningCharacteristicpercent (%) unless otherwise notedAll Women 40-49Screen Cohort (1 or more SM)Routine Screen Cohort (3 or more SM)Patient CharacteristicsAge at Cohort entryMean (median)42.5 (40)42.8 (42)41.7 (41)Age at Cohort exitMean (median)47.3 (50)48.5 (50)49.1 (50)Family Physician at Cohort entry90.0 %92.3%94.8%Income – top quintile20.7%22.3%24%Rurality Category – most urban76.3%79.0%81.2%Birth Location – Canada74.4%72.2%71.6%Annual Health Exams: at least one51.1%72.1%75.3%Pap Smear: at least one68.4%86.6%92.9%Provider CharacteristicsFemale44.8%47.2%52.1%Canadian Graduates70.3%70.3%72.1%Fee for Service model48.0%55.0%58.8% Citation Format: Michelle B Nadler, Alex Marchand-Austin, Peter C. Austin, Alexandra Desnoyers, Brooke E. Wilson, Aisha Lofters, Noah Ivers, Eitan Amir. Patient and provider determinants of breast cancer screening among Ontario women age 40-49: A population based retrospective cohort study [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS3-17.

PURPOSE:Canadian breast cancer screening guidelines state that mammography screening for women 40-49 should be individualized based on risk assessment and preferences. This retrospective cohort study describes the frequency of screening in women aged 40-49 and identifies patient and provider-level associations with screening.METHODS:Administrative databases were linked. The overall cohort included Ontario women aged 40-49 between April 1, 2009 and March 31, 2019. Subgroups were created: the "screen" group included women who received a mammogram defined as screening (using a set of exclusion criteria) and the "routine screen" group included women with three or more screening mammograms. A multivariable multilevel logistic regression model accounting for patient and provider characteristics was fit to determine characteristics associated with routine screening. The intracluster correlation co-efficient was used to quantify the degree of variation across providers.RESULTS:Of approximately 2 million eligible women, there were 532,596 (25.5%) in the screen group and 90,651 (4.3%) the routine screen group. There was an average of 0.30 and 0.52 screening mammograms per woman year, in the screen and routine screen groups, respectively. Routine screening was associated with periodic health exams (OR 1.21, 95% CI 1.20-1.22), receiving pap smears (OR 1.38, 95% CI 1.37-1.39), and fee-for-service models of care (OR 1.32, 95% CI 1.27-1.36). Over 20% of the variation in screening was due to systematic between-provider differences.CONCLUSIONS:Approximately 4.3% of women aged 40-49 in Ontario received routine breast cancer screening with substantial variation across providers. Routine screening is associated with periodic health examinations, receipt of pap smears, and fee-for-service models of care.

Background. The role of antibiotics in preventing urinary tract infection (UTI) in older adults is unknown. We sought to quantify the benefits and risks of antibiotic prophylaxis among older adults. Methods. We conducted a matched cohort study comparing older adults (>= 66 years) receiving antibiotic prophylaxis, defined as antibiotic treatment for >= 30 days starting within 30 days of a positive culture, with patients with positive urine cultures who received antibiotic treatment but did not receive prophylaxis. We matched each prophylaxis recipient to 10 nonrecipients based on organism, number of positive cultures, and propensity score. Outcomes included (1) emergency department (ED) visit or hospitalization for UTI, sepsis, or bloodstream infection within 1 year; (2) acquisition of antibiotic resistance in urinary tract pathogens; and (3) antibiotic-related complications. Results. Overall, 4.7% (151/3190) of UTI prophylaxis patients and 3.6% (n = 1092/30 542) of controls required an ED visit or hospitalization for UTI, sepsis, or bloodstream infection (hazard ratio [HR], 1.33; 95% confidence interval [CI], 1.12-1.57). Acquisition of antibiotic resistance to any urinary antibiotic (HR, 1.31; 95% CI, 1.18-1.44) and to the specific prophylaxis agent (HR, 2.01; 95% CI, 1.80-2.24) was higher in patients receiving prophylaxis. While the overall risk of antibiotic-related complications was similar between groups (HR, 1.08; 95% CI,.94-1.22), the risk of Clostridioides difficile and general medication adverse events was higher in prophylaxis recipients (HR [95% CI], 1.56 [1.05-2.23] and 1.62 [1.11-2.29], respectively). Conclusions. Among older adults with UTI, the harms of long-term antibiotic prophylaxis may outweigh their benefits.

Objective: Selective reporting of antibiotic susceptibility test results may help guide appropriate antibiotic prescribing, particularly for urinary tract infections. Our objective was to describe laboratory urine culture susceptibility reporting practices and to estimate their impact on antibiotic prescribing in outpatients. Methods: We examined all positive urine cultures with Escherichia coli, Klebsiella pneumoniae, or Proteus mirabilis associated with an antibiotic prescription among outpatients over 65 years of age in Ontario, Canada from 2014 through 2017. We evaluated antibiotic prescribing in the empirical window (1-3 days before culture result) and in the directed window (0-5 days after culture result). Unadjusted and adjusted odds ratios were reported to estimate the association between reporting and prescribing. Results: In total 113 780 eligible urine cultures from 48 laboratories were included in the study cohort. Susceptibility reporting practices were highly variable between laboratories, with a range across antibiotics from norfloxacin (n = 5/48, 10.4% reporting) to nitrofurantoin (n = 40/48, 83.3% reporting). Reporting antibiotic susceptibility was associated with increased odds of prescribing that antibiotic in the directed window (aOR 2.98, 95%CI 2.07-4.28). At the laboratory level, the proportion of urine cultures reporting specific antibiotic susceptibility results was also associated with an increase in prescribing of that antibiotic in the empirical window (adjusted OR 1.23, 95%CI 1.13-1.33, per 25% increase in reporting). Conclusions: Laboratory reporting of antibiotic susceptibility results for urine cultures is associated with empirical and directed prescribing of the reported antibiotics. Laboratories can play an important role in guiding appropriate antibiotic selection for urinary indications. Bradley J. Langford, Clin Microbiol Infect 2021;27:568 Crown Copyright ? 2020 Published by Elsevier Ltd on behalf of European Society of Clinical Microbiology and Infectious Diseases. All rights reserved.

Background. Vaccine effectiveness (VE) studies provide essential evidence on waning vaccine-derived immunity, a major threat to pertussis control. We evaluated how study design affects estimates by comparing 2 case-control studies conducted in Ontario, Canada. Methods. We compared results from a test-negative design (TND) with a frequency-matched design (FMD) case-control study using pertussis cases from 2005-2015. In the first study, we identified test-negative controls from the public health laboratory that diagnosed cases and, in the second, randomly selected controls from patients attending the same physicians that reported cases, frequency matched on age and year. We compared characteristics of cases and controls using standardized differences. Results. In both designs, VE estimates for the early years postimmunization were consistent with clinical trials (TND, 84%; FMD, 89% at 1-3 years postvaccination) but diverged as time since last vaccination increased (TND, 41%; FMD, 74% by 8 years postvaccination). Overall, we observed lower VE and faster waning in the TND than the FMD. In the TND but not FMD, controls differed from cases in important confounders, being younger, having more comorbidities, and higher healthcare use. Differences between the controls of each design were greater than differences between cases. TND controls were more likely to be unvaccinated or incompletely vaccinated than FMD controls (P <.001). Conclusions. The FMD adjusted better for healthcare-seeking behavior than the TND. Duration of protection from pertussis vaccines is unclear because estimates vary by study design. Caution should be exercised by experts, researchers, and decision makers when evaluating evidence on optimal timing of boosters.

Objectives Although pertussis vaccines have been widely used for many decades, a burden of illness persists. Resurgences in Ontario, Canada, have not been substantial in the past decade, but an outbreak of pertussis occurred in Toronto between 1 October 2005 and 31 March 2006. Previous Ontario studies found high vaccine effectiveness (VE) in the initial years post-immunization. In order to explore the impact of outbreaks and external factors on VE, we investigated pertussis VE during the period 2006–2008. Methods We assessed pertussis VE using a frequency-matched case-control study for the period 1 March 2006 to 31 December 2008. We used logistic regression to estimate VE by age, time since last vaccination, and vaccination status according to the Ontario recommended schedule. We compared analyses including and excluding cases from Toronto, and to two recent Ontario pertussis VE studies. Results We included 1797 confirmed cases and 7188 matched controls. Most cases were under 4 years of age during the study period. Pertussis VE was 3.8% (95% CI: − 21.0, 24.0) in the period 15–364 days following the last pertussis vaccine dose, and increased with increasing time since vaccination. Pertussis VE in the first 15–364 days excluding Toronto increased to 57.1% (95% CI: 26.0, 75.1), but the trend of increasing VE with time since vaccination persisted. Although VE was higher in older (6–11 years) than younger (0–5 years) children, it was lower at 12–13 years than after 14 years. Conclusion VE was lower in comparison with other studies conducted in Ontario, particularly in younger children. Various factors occurring during the study period may have influenced the results, including clinical testing of asymptomatic contacts, laboratory testing and methods and reporting practice, and a sensitive case definition. Further studies are needed to optimize methods for measuring VE to inform pertussis vaccine policy.

Background:Drug susceptibility testing (DST) in nontuberculous mycobacterial pulmonary disease (NTM-PD) is useful for some Mycobacterium species. International guidelines recommend routine use of DST for clinically relevant mycobacteria. DST use and results are poorly studied at the population level. We sought to identify the frequency of DST utilization for nontuberculous mycobacteria (NTMs) and describe the potential relevance of these results in Ontario.Methods:Using public health laboratory data, we performed a population-based retrospective analysis of NTM DST utilization in Ontario from May 2010 to June 2015. We determined the proportion of incident NTM-PD infections for which DST was performed and analyzed minimum inhibitory concentration (MIC) distributions from NTM testing overall, using thresholds recommended by the Clinical and Laboratory Standards Institute.Results:The proportion of incident cases of NTM-PD tested for DST was 6.3% (240/3,806) for Mycobacterium avium complex (MAC), 36.2% (67/185) for M. abscessus, and 1.8% (19/1,057) for M. xenopi. Among specimens from all body sites, MAC resistance to clarithromycin occurred in 8.0% of specimens (21/262) and MAC resistance to amikacin (intravenous, MIC > 64 µg/mL) occurred in 22.6% (19/84). M. abscessus resistance occurred as follows: to amikacin, 3.8% (3/79); cefoxitin, 14.0% (11/79); imipenem, 30.4% (14/46); linezolid, 39.2% (31/79); clarithromycin, 54.2% (13/24); ciprofloxacin, 92.4% (73/79); and moxifloxacin, 91.1% (51/56). M. xenopi analysis was limited by few DST requests and a lack of DST clinical correlation.Conclusions:We found that NTM DST is underutilized in Ontario and observed a very high frequency of amikacin resistance among MAC isolates.

BACKGROUND: Ontario is 1 of 5 provinces that immunize adolescents for hepatitis B virus (HBV), despite the World Health Organization recommendation for universal birth dose vaccination. One rationale for not vaccinating at birth is that universal prenatal screening and related interventions prevent vertical transmission. The aims of our study were to evaluate the uptake and epidemiology of prenatal HBV screening, and to determine the number of children in Ontario with a diagnosis of HBV before adolescent vaccination. METHODS: We extracted data from ICES, Public Health Ontario and Better Outcomes & Registry Network (BORN) Ontario databases. We assessed prenatal screening uptake and prevalence of prenatal hepatitis B surface antigen (HBsAg) from 2012 to 2016, as well as subsequent hepatitis B e-antigen (HBeAg) and HBV DNA testing and percent positivity. We used age and region to subcategorize the results. In a separate unlinked analysis, we evaluated the number of children positive for HBV aged 0–11 years who were born in Ontario from 2003 to 2013. RESULTS: From 2012 to 2016, 93% of pregnant women were screened for HBV, with an HBsAg prevalence of 0.6%. Prevalence of HBsAg increased with age, peaking at older than 45 years at 3%. North Toronto had the highest overall prevalence of 1.5%, whereas northern Ontario had the lowest. Of women who were HBsAg positive, HBeAg and HBV DNA tests were subsequently ordered in 13% and 38%, respectively. Of children born in Ontario between 2003 and 2013, 139 of 23 759 tested positive for HBV. INTERPRETATION: Prenatal HBV screening is not universal and subsequent evaluation is poor, limiting optimal intervention and possibly contributing to some Ontario-born children being given a diagnosis of HBV before age 12 years. These findings underscore the limitations of the province’s adolescent vaccination strategy.

Evidence-based guidelines recommend the combination of macrolide–ethambutol–rifamycin as first-line treatment for Mycobacterium avium complex pulmonary disease (MAC-PD) [1]. Whether this regimen results in improved survival is unknown. No significant difference in mortality among patients treated with different antibiotic regimens for Mycobacterium avium pulmonary disease We thank IMS Brogan Inc. for use of their Drug Information Database.

Surveys suggest that clinicians diverge from guidelines when treating Mycobacterium avium complex (MAC) pulmonary disease (PD). To determine prescribing patterns, we conducted a cohort study of adults >= 66 years of age in Ontario, Canada, with MAC or Mycobacterium xenopi PD during 2001-2013. Using linked laboratory and health administrative databases, we studied the first treatment episode (>= 60 continuous days of >= 1 of a macrolide, ethambutol, rifamycin, fluoroquinolone, linezolid, inhaled amikacin, or, for M. xenopi, isoniazid). Treatment was prescribed for 24% MAC and 15% of M. xenopi PD patients. Most commonly prescribed was the recommended combination of macrolide, ethambutol, and rifamycin, for 47% of MAC and 36% of M. xenopi PD patients. Among MAC PD patients, 20% received macrolide monotherapy and 33% received regimens associated with emergent macrolide resistance. Although the most commonly prescribed regimen was guidelines-recommended, many regimens prescribed for MAC PD were associated with emergent macrolide resistance.

This study examined the evolving nature of Bordetella pertussis in Ontario, Canada, by characterizing isolates for their genotypes and expression of pertactin (PRN). From 2009 to 2017, 413 B. pertussis were cultured from pertussis cases at the Public Health Ontario Laboratory. Their genotypes were determined by partial gene sequence analysis of their virulence and (or) vaccine antigens: filamentous haemagglutinin, PRN, fimbriae 3, and pertussis toxin, including the promoter region. Expression of PRN was measured by Western immunoblot. Two predominant genotypes, ST-1 and ST-2, were found throughout the study and were responsible for 47.5% and 46.3% of all case isolates, respectively. The prevalence of ST-1 appeared to fluctuate from 80.3% in 2009 to 20.0% in 2014 and 58.5% in 2017, while the prevalence of ST-2 changed from 18.4% in 2009 to 80.0% in 2014 and 26.2% in 2017. A PRN-deficient strain was first noted in 2011 (16.7%), and its prevalence increased to 70.8% in 2016 but decreased to 46.2% in 2017. More ST-2 (46.6%) than ST-1 (16.8%) strains were associated with PRN deficiency. Newer ST-21 and ST-22 found in 2015-2017 were uniformly PRN deficient. The impact of the evolving nature of B. pertussis on disease epidemiology requires further longitudinal studies.