Abstract Objective: To determine if hospital characteristics were associated with rates of healthcare-associated (HA) viral respiratory infections (VRIs) in a large Canadian acute care hospital network. Design: Survey of hospital characteristics and prospective surveillance of HA-VRI. Setting: The Canadian Nosocomial Infection Surveillance Program is a sentinel surveillance system with 89 hospitals participating in adult and pediatric VRI surveillance. Patients Patients with laboratory confirmed infection from SARS-CoV-2, Influenza A/B or RSV associated with their hospitalization from participating hospitals between January 1-December 31, 2024. Methods: A 15-item survey was distributed to hospitals to collect information on hospital infrastructure, infection prevention and control practices, and occupational health measures for healthcare workers. HA-VRI rates/10,000 patient-days were analyzed alongside survey responses using univariable and multivariable negative binomial regression models in R to determine associations. Hospitals without case data were excluded. Results: Of 89 hospitals, 93% (n = 83) responded to the survey, with 79 included in the analysis. The national HA-VRI rate was 8.15/10,000 patient-days. Pediatric hospitals had a 56% lower HA-VRI rate than adult/mixed hospitals ( P < .001) that increased with the exclusion of SARS-CoV-2. Each 10% increase in the percentage of single-bed rooms corresponded to a 12% reduction in infection rate ( P < .001). Teaching vs. Non-teaching hospitals were associated with a 32% lower HA-VRI rate. Universal masking was not associated with a statistically significant reduction in HA-VRI rates (RR 0.82, 95% CI: 0.56–1.19). Conclusions: In a large surveillance network, lower HA-VRI rates were seen in pediatric hospitals, teaching hospitals, and in hospitals with higher proportions of single-bed rooms.

We sought to assess predictive factors for SARS-CoV-2 infectiousness using a meta-analytic approach. We searched LitCovid, medRxiv, Google Scholar, and the WHO COVID-19 database until June 30 2025, including studies which cultured SARS-CoV-2, relating them to clinico-epidemiologic and laboratory variables and RT-PCR cycle threshold (Ct) values. Using linear mixed-effects regression models, we tested for independent associations with Ct values with 95%CIs and adjusted P-values in a multivariable model. We used a modified QUADAS criteria to assess risk-of-bias. We included 50 studies, with 39 in quantitative synthesis. The percentage of culture-positive specimens decreased with increasing Ct values (subgroup test difference Q = 96.71;P < 0.001) and time since the first PCR test (Q = 26.95;P = 0.0026). Presence of symptoms (Q = 20.1;P < 0.01), gene platform used (Q = 14.89;P = 0.002), being a cancer patient (Q = 24.9;P < 0.0001), and vaccination status (Q = 8.80;P = 0.012) were associated with increased culture-positivity, whereas a rising Ct (adjusted Ct change -6.58[95%CI] -5.30, -7.86;P < 0.001) was strongly associated with culture-negativity. Analysing 186 immunocompetent patients with 1,393 Ct values, 2 consecutive Cts ≥ 30 or a rising Ct value on serial testing demonstrated a sensitivity of 87.5% and specificity of 96.3% using culture positivity as the outcome. Serial Ct monitoring, integrated with clinico-epidemiologic data is a valuable tool for assessing infectiousness, providing objective criteria for discontinuing isolation and guiding clinical decisions.

Methicillin-resistant Staphylococcus aureus (MRSA) is a prevalent bacterium in medical settings. It can result in bloodstream infections and other severe illnesses, and patients may have a high risk of dying from these conditions. This study aimed to examine MRSA transmission in hospitals across Alberta and how undetected colonized patients on admission affect MRSA spread. We used a Bayesian compartmental model to simulate MRSA spread across 106 acute care hospitals in Alberta. The model assumes that MRSA spreads through interactions between susceptible individuals and MRSA patients, including both hospital-acquired (HA) and community-acquired (CA) MRSA cases. Data from Edmonton, Calgary, rural Alberta and all regions in Alberta were used to fit the model. We also assumed that a small percentage of patients were colonized upon admission but were not promptly identified in hospitals, and we tested the model assumptions. Transmission rates were estimated using a Bayesian framework with Markov chain Monte Carlo (MCMC) algorithms. We compared transmission rates across several regions in Alberta and assessed the effect of MRSA prevalence at hospital admission on MRSA transmission. When the model fit the data in hospitals in all areas of Alberta, the average number of susceptible people colonized due to patients with HA-MRSA colonization, patients with HA-MRSA infections, patients with CA-MRSA colonization, and patients with CA-MRSA infections per contact per month are around 0.03 (95

Importance:The Bacteremia Antibiotic Length Actually Needed for Clinical Effectiveness (BALANCE) trial showed that 7 days of antibiotics was noninferior to 14 days among patients with bacteremia. However, it is unknown whether patients with high serum procalcitonin (PCT) level at day 7 of therapy would benefit from a prolonged treatment course. Objective:To investigate whether an elevated serum PCT level at day 7 of bacteremia was associated with increased mortality among patients treated with 7 vs 14 days of antibiotics. Design, Setting, and Participants:This cohort study was a planned secondary analysis of the BALANCE trial from 2014 to 2023, a multicenter randomized clinical trial where serum was collected on day 7 of bacteremia and patients were followed up for 90 days after study enrollment. Serum samples were collected from patients 7 days after initiation of antibiotics; PCT levels were later quantified by an antibody-based assay and therefore were not available to clinicians. Data were analyzed from January to June 2025. Intervention:Patients were randomized to receive either 7 or 14 days of antibiotics. Antibiotic selection, dosing, and route were at the discretion of the treating team. Main Outcomes and Measures:The primary outcome was defined as death from any cause within 90 days of the positive index blood culture result. Secondary outcomes included death by any cause while admitted to the ICU, death by any cause while admitted to the hospital, number of days alive and not admitted to the ICU within 28 days of the index positive blood culture, number of days alive and not admitted to hospital within 28 days of the index positive blood culture, and the duration of mechanical ventilation. Results:A total of 125 patients (median age 63, [IQR, 58-79] years; 80 [64.0%] male) were included in this study. Sixty-five participants (52%) had low PCT levels (<250 pg/mL) and 60 (48%) had high PCT levels (≥250 pg/mL) on day 7. The high PCT group was older, had more comorbidities, and had a higher prevalence of community-acquired bacteremia. Ninety-day mortality was higher in the high vs low PCT group: 21.6% (13 of 60) vs 6.2% (4 of 65) (absolute risk difference [ARD] 15.5%; 95% CI, 3.6%-27.5%). Among patients with high PCT level, 90-day mortality was not different among participants with 7 vs 14 days of antbiotics (ARD, -19.9%; 95% CI, -1.7 to 41.7). Conclusions and relevance:In this cohort study, elevated PCT level on day 7 was associated with increased 90-day mortality. However, prolonging antibiotics beyond 7 days was not associated with improved mortality in patients with a residually high PCT level. Seven days of antibiotics appears sufficient for most patients with bloodstream infections independent of day 7 serum PCT level.

Importance The Bacteremia Antibiotic Length Actually Needed for Clinical Effectiveness (BALANCE) trial showed that 7 days of antibiotics was noninferior to 14 days among patients with bacteremia. However, it is unknown whether patients with high serum procalcitonin (PCT) level at day 7 of therapy would benefit from a prolonged treatment course. Objective To investigate whether an elevated serum PCT level at day 7 of bacteremia was associated with increased mortality among patients treated with 7 vs 14 days of antibiotics. Design, Setting, and Participants This cohort study was a planned secondary analysis of the BALANCE trial from 2014 to 2023, a multicenter randomized clinical trial where serum was collected on day 7 of bacteremia and patients were followed up for 90 days after study enrollment. Serum samples were collected from patients 7 days after initiation of antibiotics; PCT levels were later quantified by an antibody-based assay and therefore were not available to clinicians. Data were analyzed from January to June 2025. Intervention Patients were randomized to receive either 7 or 14 days of antibiotics. Antibiotic selection, dosing, and route were at the discretion of the treating team. Main Outcomes and Measures The primary outcome was defined as death from any cause within 90 days of the positive index blood culture result. Secondary outcomes included death by any cause while admitted to the ICU, death by any cause while admitted to the hospital, number of days alive and not admitted to the ICU within 28 days of the index positive blood culture, number of days alive and not admitted to hospital within 28 days of the index positive blood culture, and the duration of mechanical ventilation. Results A total of 125 patients (median age 63, [IQR, 58-79] years; 80 [64.0%] male) were included in this study. Sixty-five participants (52%) had low PCT levels (<250 pg/mL) and 60 (48%) had high PCT levels (≥250 pg/mL) on day 7. The high PCT group was older, had more comorbidities, and had a higher prevalence of community-acquired bacteremia. Ninety-day mortality was higher in the high vs low PCT group: 21.6% (13 of 60) vs 6.2% (4 of 65) (absolute risk difference [ARD] 15.5%; 95% CI, 3.6%-27.5%). Among patients with high PCT level, 90-day mortality was not different among participants with 7 vs 14 days of antbiotics (ARD, −19.9%; 95% CI, −1.7 to 41.7). Conclusions and relevance In this cohort study, elevated PCT level on day 7 was associated with increased 90-day mortality. However, prolonging antibiotics beyond 7 days was not associated with improved mortality in patients with a residually high PCT level. Seven days of antibiotics appears sufficient for most patients with bloodstream infections independent of day 7 serum PCT level.

OBJECTIVE:Vancomycin-resistant Enterococcus (VRE) is an important cause of healthcare-associated infections. We adapted wastewater-based surveillance as a tool to longitudinally monitor VRE in hospitals through the detection of vancomycin resistance genes vanA and vanB. METHODS:Wastewater from four tertiary-care hospitals (three adult and one pediatric, totaling >2300 inpatient beds) and all three municipal wastewater treatment plants (WWTP) in Calgary, Canada (∼1.8 million) was sampled weekly (March to September 2022) and every other week (September 2022 to March 2023). Wastewater pellets were collected, DNA extracted, and vanA and vanB quantified by qPCR. vanA and vanB gene copies were assessed as raw (copies/mL) and normalized with three different fecal biomarkers - total bacterial 16S-rRNA, Bacteroides HF183 16S-rRNA, and human 18S-rRNA. Raw and normalized vanA and vanB abundance from each site was compared with clinically identified infections, vancomycin prescribing and hemodialysis services. RESULTS:The abundance of vanA was up to 1085-fold higher (p < 0.0001, Mann-Whitney) and vanB up to 32-fold higher (p < 0.01, Mann-Whitney) in adult hospitals compared to an aggregate municipal signal and exhibited significantly greater variation. Strong correlations between each method of fecal normalization and raw-measured vanA and vanB were observed, and no normalization method proved superior (Spearman's r = 0.50-0.96, p < 0.0001). vanA abundance was strongly correlated with hemodialysis provision (Spearman's r = 0.8357, p < 0.0001) but not vancomycin prescribing. CONCLUSIONS:Wastewater-based surveillance is a comprehensive tool capable of longitudinal real-time hospital surveillance for VRE with the potential to transform the ability of infection control and antimicrobial stewardship programs to dynamically track, understand, and mitigate nosocomial antimicrobial-resistant pathogens.

Methicillin-resistant Staphylococcus aureus (MRSA) is a bacterium that leads to severe infections in hospitalized patients. Previous epidemiological research has focused on MRSA transmission, but few studies have examined the influence of both hospital-acquired MRSA (HA-MRSA) and community-acquired MRSA (CA-MRSA) on MRSA spread in hospitals. In this study, we present a unique compartmental model for studying MRSA transmission patterns in hospitals in Edmonton, Alberta. The model consists of susceptible individuals, patients who have been colonized or infected with HA-MRSA or CA-MRSA, and isolated patients. We first use Bayesian inference with Markov chain Monte Carlo (MCMC) algorithms to estimate the posterior mean of parameters in the full model using data from hospitals in Edmonton. Then we develop multiple sub-models with varying assumptions about the origin of new MRSA colonization. We also estimate transmission rates in hospitals.

BACKGROUND:Long-term care (LTC) residents are vulnerable to invasive infection. Appropriate use and training on personal protective equipment (PPE) is important for protecting residents and healthcare workers (HCWs). Studies on the barriers and facilitators to PPE use are limited in LTC settings. AIM:To characterize HCWs' perceptions of barriers and facilitators to the uptake and appropriate use of PPE in LTC facilities in Calgary, Alberta. METHODS:Semi-structured interviews were conducted with HCWs from April to October 2022. Interview transcripts were analysed deductively to identify themes from the Theoretical Domains Framework. FINDINGS:Seven HCWs were interviewed. Barriers and facilitators fell within six overarching themes including: availability and quality of PPE; knowing how to use PPE; familial obligations; convenience and comfort; sense of professional duty; and social influences and identity. Additional factors such as understaffing and the need for more training sessions were highlighted. Strategies to improve PPE use were identified by HCWs, including the use of PPE champions, regular audits, and constructive feedback. CONCLUSION:Identification of unique barriers and facilitators regarding PPE use by HCWs in LTC will facilitate targeted interventions to improve PPE use in this setting.

Staphylococcus aureus bacteremia is a leading cause of morbidity and mortality. Several phenotypes (e.g. methicillin-resistance) influence patient outcomes. The high inoculum effect (HIE) is characterized by reduced susceptibility to beta-lactam antibiotics, most notably cefazolin, at high inoculums in-vitro . A population-based cohort was used to assess all MSSA bacteremia in Calgary, Alberta, from 2012-14 and 2019 (n=1.5 million). Isolates underwent genomic sequencing and cefazolin susceptibility testing at 10 5 and 10 7 CFU/ml where the HIE was defined as a 4X-increase in minimum-inhibitory concentration (MIC) and pronounced (PIE) defined as MIC≥16 ug/ml at 10 7 CFU/ml. The incidence of MSSA bacteremia with HIE decreased from 38.9 to 24.2% between the two time periods. Patients infected with HIE phenotype could not be differentiated based on demographics, source of bacteremia, or clinical biomarkers at presentation. Sequencing confirmed associations of HIE with blaZ A, agr3, and clonal complex 30. HIE was not associated with outcomes including clearance-time and all-cause mortality when assessed in aggregate or as a function of treatment. Relapses, however, were only documented with cefazolin. PIE was observed in 3.7% of isolates and was associated with significant increased all-cause 180-day mortality, irrespective of treatment, but not at one year. The HIE, but not PIE, is common in an unselected general population cohort. Neither demographics nor clinical biomarkers can be used to predict HIE. If there is a deleterious impact of this phenotype on patient outcomes, it is modest and may be masked by empiric therapy provided prior to MSSA bacteremia confirmation. A prospective cohort study by Miller et al. (2018) observed a significant increase in 30-day mortality in individuals experiencing methicillin-sensitive Staphylococcus aureus (MSSA) bacteremia, with isolates exhibiting the high-inoculum effect (HIE) phenotype, when treated with the cefazolin. Our study sought to understand the epidemiology and impact of the HIE, using a population-based study design thereby mitigating the selection bias associated with other conventional cohort studies (focused on specific hospitals, at-risk groups, or clinics). We address the effects of HIE on clinical outcomes, predictive factors, and associated genomic contributors for the HIE phenotype within an unbiased population. These data are important for clinicians by highlighting if it is possible to predict HIE phenotype based on clinical and genomic factors, and to establish if cefazolin use associates with worse outcomes when MSSA causing bacteremia exhibits the HIE phenotype.

Understanding factors associated with antimicrobial resistance (AMR) distribution across populations is a necessary step in planning mitigation measures. While associations between AMR and socioeconomic-status (SES), including employment and education have been increasingly recognized in low- and middle-income settings, connections are less clear in high-income countries where SES remains an important influence on other health outcomes. We explored the relationship between SES and AMR in Calgary, Canada using spatially-resolved wastewater-based surveillance of resistomes detected by metagenomics across eight socio-economically diverse urban neighborhoods. Resistomes were established by shotgun-sequencing of wastewater pellets, and qPCR of targeted-AMR genes. SES status was established using 2021 Canadian census data. Conducting this comparison during the height of COVID-related international travel restrictions (Dec. 2020–Oct. 2021) allowed the hypotheses linking SES and AMR to be assessed with limited confounding. These were compared with sewage metagenomes from 244 cities around the world, linked with Human Development Index (HDI). Wastewater metagenomes from Calgary’s socioeconomically diverse neighborhoods exhibit highly similar resistomes, with no quantitative differences (p > 0.05), low Bray-Curtis dissimilarity, and no significant correlations with SES. By comparison, dissimilarity is observed between globally-sourced resistomes (p < 0.05), underscoring the homogeneity of resistomes in Calgary’s sub-populations. The analysis of globally-sourced resistomes alongside Calgary’s resistome further reveals lower AMR burden in Calgary relative to other cities around the world. This is particularly pronounced for the most clinically-relevant AMR genes (e.g., beta-lactamases, macrolide-lincosamide-streptogramin). This work showcases the effectiveness of inclusive and comprehensive wastewater-based surveillance for exploring the interplay between SES and AMR. Antimicrobial resistance (AMR) occurs when antimicrobial treatments fail to work and microbes continue to grow. This is a result of microbes acquiring AMR genes. Antimicrobial resistance (AMR) is an increasing public health threat. Some studies have suggested an association between AMR and socioeconomic factors. The amount of AMR can be monitored by investigating the presence of specific genes indicative of AMR in wastewater. To explore this within a high-income country with publicly funded health care, we collected wastewater from eight socioeconomically diverse neighborhoods across a large Canadian city. Conducted over eleven months during COVID-19-related travel restrictions, we did not observe an association between socioeconomic status of residents and the amount or types of AMR genes in wastewater. We also compared AMR genes from wastewater from cities across the globe, where we observed the presence of AMR genes significantly differed along established socio-economic parameters. Overall, our findings revealed the relationship between AMR genes and socioeconomic factors is dynamic, and context dependent. Lee et al. investigate whether the wastewater resistome of a large Canadian city associates with socioeconomic status (SES) of resident populations using a granular, neighborhood-based approach. No correlation is seen, in contrast with data from other cities around the world, where AMR genes disproportionately concentrate in cities with lower SES.

Background:The BALANCE trial demonstrated non-inferiority of 7 (vs 14) day antibiotic durations in patients with uncomplicated non-S. aureus/lugdunensis bacterial bloodstream infections (BSI). However, there may be patient subgroups who benefit from longer durations. We aimed to evaluate if bedside clinical decision rules could identify these subgroups. Methods:In this post-hoc analysis of the multicentre, randomised BALANCE trial (October 17, 2014-May 5, 2023), we applied three clinical decision rules to investigate heterogeneity of treatment effect in 7-day vs 14-day antibiotic durations on 90-day all-cause mortality. We used the rules to categorize patients in BALANCE into different risk groups and calculated the unadjusted absolute risk difference (RD) for 90-day mortality in patients receiving 7- vs 14-day antibiotics within each risk group. Statistical significance was tested using an interaction test. The BALANCE trial is registered with ClinicalTrials.gov (NCT03005145). Findings:3581 patients were included. All three rules predicted mortality risk, but none identified statistically significant effect modification: (a) static rule (low-risk: RD -0.58, 95% CI -8.91 to 7.73; moderate-risk: RD -.01, 95% CI -3.86 to 1.83; high-risk: RD -2.65, 95% CI -7.12 to 1.81; p = 0.74); (b) dynamic rule (met rule on day 7: RD -2.18, 95% CI -4.81 to 0.45; did not meet rule: RD 1.75, 95% CI -3.89 to 7.40; p = 0.16); and (c) early clinical failure criteria (score<2: RD -2.38, 95% CI -5.0 to 0.23; score ≥2: RD -0.65, 95% CI -5.06 to 3.77; p = 0.24). Results were consistent across sensitivity analyses including imputation for missing data and restricting analyses to gram-negative BSI. Interpretation:The decision rules included in our analyses did not identify a subgroup of patients within BALANCE that would benefit from 14 (vs 7) days of treatment. 7-day treatment duration is sufficient for most patients with uncomplicated non-S. aureus/lugdunensis BSI. Future research could explore data-driven machine-learning approaches to identify comprehensive combinations of patient characteristics that may guide individualised duration of antibiotic therapy. Funding:The BALANCE trial was funded by the Canadian Institutes of Health Research, Health Research Council of New Zealand, Australian National Medical Research Council, Physicians Services Incorporated Ontario and Ontario Ministry of Health and Long-term Care Innovation Fund. SWXO conducted this study as part of his PhD studies, with funding from: the Emerging & Pandemic Infections Consortium (University of Toronto, Canada); Connaught International Scholarship (University of Toronto, Canada); the Queen Elizabeth II Graduate Scholarship in Science and Technology (QEII-GSST; Government of Ontario, Canada); and the Melbourne Research Scholarship (University of Melbourne, Australia). VML is supported by Clinical Research Scholar-Junior 2 program (FRQ-S).

Rigorous method development and validation to detect and quantify SARS-CoV-2 RNA in wastewater has led to important advances in community disease surveillance using quantitative molecular biology tools. Despite this progress, agreement on standardized workflows for this important public health objective has been elusive. Multiple studies have compared different protocols but have been limited by short periods of observation or low numbers of test sites. Here we compare results from two parallel workflows for wastewater processing and quantifying SARS-CoV-2 gene targets from five wastewater treatment plants in three large cities in Alberta, Canada for up to 29-months. In total 1,482 wastewater samples were processed using either affinity columns followed by RT-qPCR with DNA-based standards or using ultrafiltration followed by RT-qPCR with RNA-based standards. Results from either workflow correlated well with each other, and with 5-day rolling averages of clinically diagnosed COVID-19 cases (i.e., in the early part of the 29-month study period when clinical testing was performed routinely). This highlights that different workflows both effectively and reliably monitored SARS-CoV-2 trends in wastewater. Parallel quantification of pepper mild mottle virus genomes and normalization were inconsistent between the two workflows, suggesting that normalization strategies may require adjustment for different wastewater processing protocols. Freezing wastewater samples diminished measured SARS-CoV-2 RNA levels significantly, whereas short term sample storage at +4°C gave consistent results. Overall, this work demonstrates that different workflows can deliver similarly effective wastewater-based surveillance for community COVID-19 burden. As this emerging technology is used more routinely, investigators should prioritize consistent application of a given workflow to a high-quality standard over time, whereas focusing on all testing programs adopting identical workflows and methods may be unnecessary.

Background: Effective integration of antimicrobial resistant organism (ARO) admission screening into clinical information systems (CIS) can facilitate prompt identification of patients at risk of an ARO and interrupt transmission. However, ARO admission screening remains suboptimal in Alberta, Canada following implementation of the ARO admission screening tool in the provincial CIS. We sought to understand the determinants of adherence with the use of the ARO admission screening tool in the CIS. Methods: A mixed-methods study was conducted using a survey, human factors observations, and qualitative focus groups. Eligible participants included nursing staff and physicians from emergency departments and inpatient units in acute care and acute rehabilitation facilities where the ARO admission screening tool was utilized in the CIS in Alberta, Canada from September 6, 2023 to June 18, 2024 (n=100). A survey (REDCap) explored staff perceptions and experiences using the tool in the CIS. Observations and interviews of nursing staff completing the tool were guided by the Systems Engineering Initiative for Patient Safety model. Virtual (Zoom) semi-structured focus groups explored barriers and enablers of using the tool guided by the Theoretical Domains Framework. Descriptive analysis of survey responses was conducted using Microsoft Excel (Version 2409). Field notes and focus group transcripts were used for a rapid qualitative, thematic analysis. A weaving narrative by theme was used to integrate survey results with findings from the observations and focus groups. Results: There were 527 survey respondents representing all 5 health zones, 5 nurses observed and 20 interviews conducted by the human factors team, and 24 participants in 6 focus groups. Focus group participants represented different sized hospitals (12-1,099 beds) with varying ARO admission adherence rates (29-83%). Three emergent themes arose: context, the ARO admission screening tool, and the individual. Contextual factors included time constraints, increasing nursing workload, competing priorities, lack of patient cooperation, and a need to increase interactions with infection prevention and control programs. Attributes of the tool impacting completion included location of the tool within the CIS, lack of prompts, and multiple sources of information required to complete the tool. At an individual level, themes arose related to experience, perceptions of ARO screening, and lack of training that influenced completion of the tool. Conclusions: Among the emergent themes, multiple determinants were identified influencing the use of the ARO admission screening tool in the provincial CIS. These findings will help inform future strategies to improve ARO admission screening and reduce ARO transmission.

Respiratory viral infection (RVI) outbreaks pose a significant threat to health. They are associated with patient morbidity and mortality, staff absenteeism, and financial burden on the healthcare system. There is a need for strategies to reduce RVI transmission in hospitals. One proposal is implementation of continuous masking policies. However, the effectiveness of such policies in mitigating RVI spread is unclear. We conducted a systematic review of the literature to determine the effectiveness of continuous masking in reducing the incidence and transmission of RVIs amongst patients and healthcare workers (HCWs) in hospitals. We systematically searched for original articles published between 2000-2024 according to a pre-determined search criterion. Studies were screened by two reviewers in Covidence. One reviewer extracted the data from eligible studies into a pre-determined data extraction form. For studies that reported only count data, results were summarized narratively. Meta-analysis to pool unadjusted or adjusted outcome measures for studies that report a statistical comparison between masking policies and transmission of infections will be considered if appropriate. Joanna Briggs Institute tools will be used for critical appraisal. 3691 studies were identified. 17 met eligibility criteria. 12 studies were conducted in single-center adult hospitals. 4 studies were conducted in pediatric hospitals, with 2 in neonatal centers. One study was conducted on a hospital system. The studied infections were influenza A/B, parainfluenza 1-3, adenovirus, respiratory syncytial virus (RSV), traditional human coronavirus strains, human metapneumovirus, SARS-CoV-2, and rhinovirus/enterovirus. Eight studies assessed the impact of a masking policy on infection rate in patients. All 8 reported masking policies reduce RVI transmission in patients. 9 studies assessed the impact of a masking policy on infection rate in HCWs. 7 were associated with reductions in RVI transmission in HCWs, whereas 2 showed no statistically significant change. The studies identified in this systematic review were associated with a reduction in RVI transmission with the use of continuous masking amongst patients. The evidence for continuous masking was less consistent for preventing RVI transmission amongst HCW with two studies reporting it was not effective. Our findings suggest that masking policies may play a role in RVI prevention but there are significant limitations with the use of observational design and masking in conjunction with other prevention measures. However, assessment of the quality of the papers is pending. Future directions will include assessing secondary outcomes like masking adherence and assessing adjusted analyses form confounding which are critically important.

Background:Oxacillin-susceptible methicillin-resistant Staphylococcus aureus (OS-MRSA) is a phenotype of S. aureus that presents as methicillin susceptible on traditional screening tests but may have a resistant phenotype, leading to clinical failure. Methods:An isolate of S. aureus screened negative for methicillin resistance in a case of septic bursitis in a 75-year-old female. After failure to improve on cefazolin, a second aspirate was performed and sent for testing. The second sample strain retrieved had an additional PBP2a lateral flow performed, demonstrating the presence of mecA products. Results:Both S. aureus isolates proved to be identical on pulsed-field gel electrophoresis and had faint positive PBP2a bands on lateral flow, despite screening negative for methicillin resistance on oxacillin and cefoxitin testing. A point mutation was found in the mecA start codon, which could explain the OS-MRSA phenotype. Neither oxacillin nor cefoxitin screening tests were positive following a cefoxitin induction assay that was used locally to promote a methicillin-resistant phenotype in small-colony variant S. aureus (SCV). Conclusions:OS-MRSA is a rare but documented phenotype of S. aureus that has the potential to escape typical screening. Simple mutations may lead to reversal under selection pressure. Failure to respond to standard-of-care therapy for methicillin-sensitive S. aureus should prompt additional testing. Such methods could include a PBP2a immunoassay with high sensitivity. The patient recovered by using an antibiotic of a different class, trimethoprim-sulfamethoxazole, for which the isolate tested sensitive.

Abstract Background Shigatoxin-producing E. coli (STEC) are responsible for significant human morbidity, with the potential to cause severe food-borne illness and outbreaks. STEC incidence varies between communities and peaks in summer months (PMID 31652648). Leveraging a SARS-CoV-2 WBS program, we sought to explore genomic targets for STEC WBS.Figure 1.Prevalence of STEC differs across Alberta’s municipal sewer sheds Methods Composite-24h wastewater (WW) was collected from geographically disparate, and socioeconomically diverse Alberta communities (n=5) at the level of municipal WW treatment plants. From 04/2022-03/2024, monthly WW underwent pelleting and DNA extraction by Qiagen DNeasy PowerSoil Pro kit. WW extracts were assessed for four potential genomic STEC targets: Shiga Toxin 1 (stx1), Shiga Toxin 2 (stx2), Intimin (eae) and LPS O antigen gene specific for O157 (rfbEO157), by multiplex PCR. Each target was normalized by 16S rRNA-for total bacterial burden. WW STEC targets were assessed for correlation using Spearman’s and compared between communities and seasonality (July-Sept vs Jan-Mar) by Mann-Whitney U-test.Figure 2.STEC WBS demonstrates seasonal prevalence trends Results Of 111 WW samples assessed, 108 (97%) were positive for all targets, and individual targets were identified in 110 (99%) stx1; 110 (99%;) stx2; 111 (100%) eae, and 110 (99%) rfbEO157. Gene abundance for each STEC target exhibited strong correlations across sites (stx1 vs stx2, r=0.802, p< 0.0001; stx2 vs rfbEO157, r=0.634, p< 0.0001; eae vs rfbEO157, r =0.551, p< 0.0001; stx2 vs. eae r=0.542, p< 0.0001). WW measured STEC gene targets exhibited significant differences between municipalities (Figure 1) with strong seasonal trends (Figure 2). Conclusion WBS for STEC yielded patterns consistent with established patterns of disease (PMID 31652648). All four STEC genomic targets demonstrated significant correlation across sewersheds. STEC WBS may represent a novel tool to understand and monitor population-level activity and prevent disease. Disclosures All Authors: No reported disclosures

Antimicrobial resistance is an accelerating threat to global health. Wastewater-based surveillance (WBS) enables objective, inclusive, and comprehensive assessments of population-level antimicrobial resistance; however, it is limited in its ability to detect rare antibiotic resistance genes (ARG). We compared traditional high-depth metagenomic sequencing of raw wastewater with lower-depth sequencing following semi-selective culture enrichment for gram negatives for rare ARGs in wastewater from two tertiary-care hospitals and two nearby urban neighborhoods. In total, 26 antibiotic resistance gene types (1,225 subtypes) were identified, with beta-lactamase genes being the most prevalent. Resistomes differed between raw and culture-enriched wastewater metagenomes and clustered based on sample type (hospitals versus neighborhoods). Hospital wastewater had higher diversity and a greater abundance of ARGs relative to both raw and culture-enriched neighborhood wastewater metagenomes. Lower coverage sequencing following culture enrichment proved superior to deeper sequencing for identifying rare, clinically relevant targets, including carbapenemase genes. In particular, enrichment with meropenem proved the most sensitive to identifying clinically relevant genes and enabled significant cost savings. ARG WBS has enormous potential for augmenting hospital-based infection prevention and control and antimicrobial stewardship programs.IMPORTANCEAntimicrobial resistance (AMR) poses a considerable burden to healthcare systems and contributes to increased morbidity and mortality. This is expected to further increase with time. AMR surveillance programs are key to understanding and controlling this progressive threat. Wastewater-based surveillance (WBS) is an emerging tool that can be adapted to this end. This study explores the role of metagenomic analysis of WBS with/and without culture enrichment to detect rare antibiotic resistance genes (ARG) of clinically important pathogens across a range of scales. We were able to demonstrate that the resistome of hospitals significantly differs from communities having a greater abundance, and more heterogeneous ARGs. Culture enrichment, particularly with meropenem, improved the detection of clinically relevant ARGs even at lower sequencing depths. WBS is an important tool with the capacity to augment hospital-based infection control and antimicrobial stewardship programs, providing real-time, cost-effective information on the population within.

Background: Adherence with antimicrobial resistant organism (ARO) admission screening is suboptimal, despite clinical support tools in clinical information systems (CIS) to facilitate the process. Behaviour change techniques to improve adherence are needed. However, in a resource-constrained healthcare system, strategies that motivate healthcare workers (HCWs) to align their practices with infection prevention and control (IPC) policies need to be prioritized. Methods: An online survey (REDCap) and a virtual (Zoom) consensus meeting using a modified nominal group technique with online voting was conducted among HCWs, IPC, and the CIS staff in September and October 2024, respectively, to achieve consensus on a prioritized list of interventions to improve ARO admission screening at acute care and acute rehabilitation facilities (n=100) in Alberta, Canada. Interventions from the Behaviour Change Wheel were mapped to barriers/enablers influencing screening adherence. Each intervention was judged across the APEASE criteria (Acceptability, Practicality, Effectiveness, Affordability, Side Effects, Equity) using a 5-point Likert Scale. Consensus to include interventions required >4 criteria with >80% agreement, consensus to exclude required >4 criteria with 80%. Interventions that did not reach consensus were discussed to determine whether to include in the final candidate list. Attendees were asked to vote on their top three interventions from the final candidate list. Results: There were 15 barriers and one enabler to ARO admission screening, mapped to 43 unique interventions. Of these, 16 interventions addressed more than one barrier/enabler, while 27 interventions only addressed a single barrier. Fifty-nine respondents completed the survey. Most respondents (63%) were IPC staff, 20% were nurses, and 17% were other HCWs (including IPC physicians). Nine interventions met criteria to include in the candidate list, 26 were excluded, and 8 interventions did not reach consensus in the survey and were discussed. There were 32 attendees at the consensus meeting (53% IPC staff and physicians, 34% clinical staff, 13% other provincial teams). Three interventions were selected: 1) creating a nursing task to complete the tool in the CIS when an admission order is signed, 2) add a banner on the CIS Storyboard when the tool is not complete, and 3) develop a best practice guideline for frontline staff on ARO admission screening. Conclusions: The survey and consensus meeting were efficient methods to determine a prioritized list of interventions, which will be implemented and evaluated, to improve ARO admission screening in Alberta.