The use of multiple hypothesis-generating methods in an outbreak investigation of Escherichia coli O121 infections associated with wheat flour, Canada 2016-2017.

A Canadian outbreak investigation into a cluster of Escherichia coli O121 was initiated in late 2016. When initial interviews using a closed-ended hypothesis-generating questionnaire did not point to a common source, cases were centrally re-interviewed using an open-ended approach. The open-ended interviews led cases to describe exposures with greater specificity, as well as food preparation activities. Data collected supported hypothesis generation, particularly with respect to flour exposures. In March 2017, an open sample of Brand X flour from a case home, and a closed sample collected at retail of the same brand and production date, tested positive for the outbreak strain of E. coli O121. In total, 76% (16/21) of cases reported that they used or probably used Brand X flour or that it was used or probably was used in the home during their exposure period. Crucial hypothesis-generating techniques used during the course of the investigation included a centralised open-ended interviewing approach and product sampling from case homes. This was the first outbreak investigation in Canada to identify flour as the source of infection.

Relationship between enteric pathogens and acute gastroenteritis disease severity: a prospective cohort study.

OBJECTIVES: To evaluate the relationship between individual bacterial and viral pathogens and disease severity. METHODS: Children <18 years with three or more episodes of vomiting and/or diarrhoea were enrolled in two Canadian paediatric emergency departments between December 2014 and August 2016. Specimens were analysed employing molecular panels, and outcome data were collected 14 days after enrolment. The primary outcome was severe disease over the entire illness (symptom onset until 14-day follow-up), quantified employing the Modified Vesikari Scale (MVS) score. The score was additionally analysed in two other time periods: index (symptom onset until enrolment) and follow-up (enrolment until 14-day follow-up). RESULTS: Median participant age was 20.7 (IQR: 11.3, 44.2) months; 47.4% (518/1093) and 73.4% (802/1093) of participants had index and total MVS scores ≥11, respectively. The most commonly identified pathogens were rotavirus (289/1093; 26.4%) and norovirus (258/1093; 23.6%). In multivariable analysis, severe disease over the entire illness was associated with rotavirus (OR = 9.60; 95%CI: 5.69, 16.19), Salmonella (OR = 6.61; 95%CI: 1.50, 29.17), adenovirus (OR = 2.53; 95%CI: 1.62, 3.97), and norovirus (OR = 1.43; 95%CI: 1.01, 2.01). Pathogens associated with severe disease at the index visit were: rotavirus only (OR = 6.13; 95%CI: 4.29, 8.75), Salmonella (OR = 4.59; 95%CI: 1.71, 12.29), adenovirus only (OR = 2.06; 95%CI: 1.41, 3.00), rotavirus plus adenovirus (OR = 3.15; 95%CI: 1.35, 7.37), and norovirus (OR = 0.68; 95%CI: 0.49, 0.94). During the follow-up period, rotavirus (OR = 2.21; 95%CI: 1.50, 3.25) and adenovirus (OR = 2.10; 95%CI: 1.39, 3.18) were associated with severe disease. CONCLUSIONS: In children presenting for emergency department care with acute gastroenteritis, pathogens identified were predominantly viruses, and several of which were associated with severe disease. Salmonella was the sole bacterium independently associated with severe disease.

CPHLN recommendations for the laboratory detection of Shiga toxin-producing Escherichia coli (O157 and non-O157).

Shiga toxin-producing Escherichia coli (STEC) are important enteric pathogens responsible for sporadic cases and outbreaks of gastroenteritis. E.coli O157:H7/NM (STEC O157) are the most commonly known STEC serotypes but it is now increasingly apparent that non-O157 STEC serotypes have been underreported in the past because they were not part of routine screening in many front-line laboratories. The Canadian Public Health Laboratory Network (CPHLN) has identified the need for improved detection and surveillance of non-O157 STEC and has developed the following recommendations to assist in the decision-making process for clinical and reference microbiology laboratories. These recommendations should be followed to the best of a laboratory's abilities based on the availability of technology and resources. The CPHLN recommends that when screening for the agents of bacterial gastroenteritis from a stool sample, front-line laboratories use either a chromogenic agar culture or a culture-independent diagnostic test (CIDT). CIDT options include nucleic acid amplification tests (NAATs) to detect Shiga toxin genes or enzyme immunoassays (EIAs) to detect Shiga toxins. If either CIDT method is positive for possible STEC, laboratories must have a mechanism to culture and isolate STEC in order to support both provincial and national surveillance as well as outbreak investigations and response. These CPHLN recommendations should result in improved detection of STEC in patients presenting with diarrhea, especially when due to the non-O157 serotypes. These measures should enhance the overall quality of healthcare and food safety, and provide better protection of the public via improved surveillance and outbreak detection and response.

International outbreak of multiple Salmonella serotype infections linked to sprouted chia seed powder - USA and Canada, 2013-2014.

Salmonella is a leading cause of bacterial foodborne illness. We report the collaborative investigative efforts of US and Canadian public health officials during the 2013-2014 international outbreak of multiple Salmonella serotype infections linked to sprouted chia seed powder. The investigation included open-ended interviews of ill persons, traceback, product testing, facility inspections, and trace forward. Ninety-four persons infected with outbreak strains from 16 states and four provinces were identified; 21% were hospitalized and none died. Fifty-four (96%) of 56 persons who consumed chia seed powder, reported 13 different brands that traced back to a single Canadian firm, distributed by four US and eight Canadian companies. Laboratory testing yielded outbreak strains from leftover and intact product. Contaminated product was recalled. Although chia seed powder is a novel outbreak vehicle, sprouted seeds are recognized as an important cause of foodborne illness; firms should follow available guidance to reduce the risk of bacterial contamination during sprouting.

Canadian Public Health Laboratory Network position statement: Non-culture based diagnostics for gastroenteritis and implications for public health investigations.

As clinical laboratories transition to using culture-independent detection test (CIDT) panels for cases of acute gastroenteritis, culture of clinical specimens is becoming less common. The reduction in bacterial cultures available for public health activities is expected to hinder surveillance and outbreak response by public health laboratories at the local, provincial, national and international levels. These recommendations are intended to serve as guidelines for the implementation of CIDT panels in frontline laboratories in Canada. The United States of America has already seen a significant reduction in culture of stool specimens despite the Association of Public Health Laboratories recommendation to perform reflex culture on positive CIDT specimens. Priority public health organisms addressed in these Canadian guidelines include Shiga toxin-producing Escherichia coli, Shigella and Salmonella and, under regional circumstances, other organisms such as Campylobacter jejuni/coli and Yersinia enterocolitica. These recommendations suggest active engagement between primary diagnostic laboratories and provincial public health laboratories to determine the workflow and protocols for reflex or parallel culture. Consequently, notifiable disease definitions will also need modification, with consultation of all stakeholders. Stakeholders need to work together to enhance recovery of bacterial isolates with best practices used for stool transport and storage.

Comparing the epidemiology of hospital-acquired methicillin-resistant Staphylococcus aureus clone groups in Alberta, Canada.

Patients with methicillin-resistant Staphylococcus aureus (MRSA) clones, which were traditionally seen in the community setting (USA400/CMRSA7 and USA300/CMRSA10), are often identified as hospital-acquired (HA) infections using Infection Prevention and Control (IPC) surveillance definitions. This study examined the demographics and healthcare risk factors of patients with HA-MRSA to help understand if community MRSA clones are from a source internal or external to the hospital setting. Despite USA300/CMRSA10 being the predominant clone in Alberta, hospital clones (USA100/CMRSA2) still dominated in the acute care setting. In the Alberta hospitalized population, patients with USA400/CMRSA7 and USA300/CMRSA10 clones were significantly younger, had fewer comorbidities, and a greater proportion had none or ambulatory care-only healthcare exposure. These findings suggest that there are two distinct populations of HA-MRSA patients, and the patients with USA400/CMRSA7 and USA300/CMRSA10 clones identified in hospital more greatly resemble patients affected by those clones in the community. It is possible that epidemiological assessment overidentifies HA acquisition of MRSA in patients unscreened for MRSA on admission to acute care.

Evaluation of a Preoperative Clinic for Women With Gynecologic Cancer.

Although many patients with gynecologic cancer undergo surgery, time constraints during the preoperative consultation may affect the accuracy of the information exchange, as well as compromise the quality of the patient assessment and care plan. Both put patients at a higher risk for complications during surgery and the postoperative period. This article describes an advanced practice RN-led preoperative assessment and education clinic designed to improve the quality of preoperative preparation and postoperative outcomes of patients with gynecologic cancer.

Epidemiology of meticillin-resistant Staphylococcus aureus bloodstream infections in Alberta, Canada.

Most studies of meticillin-resistant Staphylococcus aureus (MRSA) bloodstream infection (BSI) reflect a convenience sample from a single hospital or a small group of hospitals. From April 2011 to March 2013, cases of MRSA BSI diagnosed in all hospitals in Alberta, Canada were captured prospectively. Isolates were spa typed. In total, there were 299 cases of MRSA BSI, equating to 3.95 cases per 100,000 population. Community-acquired BSI accounted for 66.9% of cases, and 33.1% of cases were hospital acquired. Cases were predominantly seen in tertiary care (36.4%) and large urban hospitals (34.3%), but were also common in regional and rural hospitals. Paediatric hospitals had very few cases (3.0%). Two clones, CMRSA 10 (USA 300; 40.2%) and CMRSA 2 (USA 100/800; 38.0%), predominated.

Weather and livestock risk factors for Escherichia coli O157 human infection in Alberta, Canada.

This study investigated the extent to which proximity to cattle and weather events in Alberta predispose human populations to E. coli O157 disease. Cases of human E. coli O157 infection in Alberta between 2004 and 2011 were obtained from the province's Communicable Disease Reporting System and Discharge Abstract Database. Regression models based on spatial area incorporated human infection data with livestock and weather covariates. A variety of regression models were applied (i.e. least squares, spatial lag/error, Poisson, negative binomial) to test the most appropriate approach. Ratios for the total number of calves, bulls and beef cows to human population were highlighted as significant cattle density variables in all final best-fitting models. Weather variables were not significant in final regression models averaged over the full study period. Our results provide evidence of a significant association between measures of cattle density and human E. coli O157 disease in Alberta.

Donor-derived bacteremia in liver transplant recipients despite antibiotic prophylaxis.

As the disparity between the number of candidates listed for transplant and the number of donors continues to grow, marginal organ donors are increasingly utilized. This includes bacteremic donors which may carry an increased risk of transmission of infection. It is recommended that recipients of organs from bacteremic donors receive antibiotic prophylaxis based on the susceptibilities of the donor isolate to prevent transmission. Here, we present four cases of donor-derived bacteremia, despite appropriate antimicrobial prophylaxis, in four liver transplant recipients. Transmitted pathogens included Staphylococcus aureus in two cases, and Escherichia coli and Group B Streptococcus each in one case. Interestingly, none of the nonhepatic organs (n=10) utilized from these bacteremic donors resulted in transmissions. These cases highlight the fact that risk of transmission from bacteremic donors is not eliminated with antimicrobial therapy in the donor and recipient. As no transmissions occurred in recipients of nonhepatic organs from these donors, these cases also suggest that liver recipients may be at higher risk of donor transmitted bacteremia.

Spatio-temporal scan statistics for the detection of outbreaks involving common molecular subtypes: using human cases of Escherichia coli O157:H7 provincial PFGE pattern 8 (National Designation ECXAI.0001) in Alberta as an example.

Molecular typing methods have become a common part of the surveillance of foodborne pathogens. In particular, pulsed-field gel electrophoresis (PFGE) has been used successfully to identify outbreaks of Escherichia coli O157:H7 in humans from a variety of food and environmental sources. However, some PFGE patterns appear commonly in surveillance systems, making it more difficult to distinguish between outbreak and sporadic cases based on molecular data alone. In addition, it is unknown whether these common patterns might have unique epidemiological characteristics reflected in their spatial and temporal distributions. Using E. coli O157:H7 surveillance data from Alberta, collected from 2000 to 2002, we investigated whether E. coli O157:H7 with provincial PFGE pattern 8 (national designation ECXAI.0001) clustered in space, time and space-time relative to other PFGE patterns using the spatial scan statistic. Based on our purely spatial and temporal scans using a Bernoulli model, there did not appear to be strong evidence that isolates of E. coli O157:H7 with provincial PFGE pattern 8 are distributed differently from other PFGE patterns. However, we did identify space-time clusters of isolates with PFGE pattern 8, using a Bernoulli model and a space-time permutation model, which included known outbreaks and potentially unrecognized outbreaks or additional outbreak cases. There were differences between the two models in the space-time clusters identified, which suggests that the use of both models could increase the sensitivity of a quantitative surveillance system for identifying outbreaks involving isolates sharing a common PFGE pattern.

Changing epidemiology of methicillin-resistant Staphylococcus aureus in Alberta, Canada: population-based surveillance, 2005-2008.

SUMMARYIncreasing prevalence of methicillin-resistant Staphylococcus aureus (MRSA) has been reported in Canada. We report the results of a prospective surveillance of MRSA infections in Alberta over a consecutive 3-year period. A total of 8910 unique clinical MRSA isolates was analysed from July 2005 to June 2008. The incidence of MRSA infection increased over the study period and was highest in males, age group ⩾85 years, and the Calgary Area. CMRSA10 (USA300) and CMRSA2 (USA100/800) were the most common PFGE strain types, representing 53·0% and 27·9% of all isolates, respectively. Significant differences were noted between MRSA strains in the source of infection and antimicrobial susceptibility. The incidence of MRSA infection in Alberta has nearly doubled in the last 3 years; this is attributed to the emergence of CMRSA10 as the predominant strain.

Prospective, randomized, controlled trial comparing lightweight versus heavyweight mesh in chronic pain incidence after TEP repair of bilateral inguinal hernia.

BACKGROUND: This prospective, clinical, randomized, controlled study was performed to define the incidence of chronic pain after total extraperitoneal (TEP) repair with a light-weighted mesh compared with heavyweight mesh in patients with bilateral inguinal hernias. METHODS: Consecutive patients with bilateral inguinal hernias were recruited for TEP inguinal hernia repair under general anesthesia. Heavyweight mesh was randomly assigned to one side of the groin and lightweight mesh to the other. Patients were followed up regularly for up to 1 year by an independent surgeon who was unaware of the mesh assignment. The postoperative pain score by means of a visual analogue scale (VAS) and other data were recorded. RESULTS: Fifty bilateral TEP hernia repairs were performed between September 2007 and February 2009. Six patients (12%) complained of chronic pain 3 months after the operation. A higher average pain score was observed for the side of hernia repaired by heavyweight mesh compared with lightweight mesh, but the difference was not statistically significant. More patients complained about foreign body sensation on the side repaired with heavyweight mesh (24%) compared with the side with lightweight mesh (8%; P < 0.05). There was no recurrence or need for reintervention for either type of mesh. CONCLUSIONS: Lightweight polypropylene mesh may be preferable to heavyweight mesh for TEP inguinal hernia repair because it provides less postoperative foreign body sensation; however, there was no significant difference in the incidence of chronic pain.

A multi-level approach for investigating socio-economic and agricultural risk factors associated with rates of reported cases of Escherichia coli O157 in humans in Alberta, Canada.

Using negative binomial and multi-level Poisson models, the authors determined the statistical significance of agricultural and socio-economic risk factors for rates of reported disease associated with Escherichia coli O157 in census subdivisions (CSDs) in Alberta, Canada, 2000-2002. Variables relating to population stability, aboriginal composition of the CSDs, and the economic relationship between CSDs and urban centres were significant risk factors. The percentage of individuals living in low-income households was not a statistically significant risk factor for rates of disease. The statistical significance of cattle density, recorded at a higher geographical level, depended on the method used to correct for overdispersion, the number of levels included in the multi-level models, and the choice of using all reported cases or only sporadic cases. Our results highlight the importance of local socio-economic risk factors in determining rates of disease associated with E. coli O157, but their relationship with individual risk factors requires further evaluation.

A comparison of three real-time PCR assays for the confirmation of Neisseria gonorrhoeae following detection of N. gonorrhoeae using Roche COBAS AMPLICOR.

Three different real-time PCR assays were evaluated as confirmatory tests for Neisseria gonorrhoeae after initial screening using the COBAS AMPLICOR Chlamydia trachomatis and N. gonorrhoeae duplex assay. The target genes used for the confirmation were the gyr, cppB and 16S rRNA genes. Analytical specificity was determined by testing 60 strains belonging to different bacterial species and/or serogroups. The primers chosen from the 16S rRNA gene for confirmation of N. gonorrhoeae were highly specific, showed no cross-reactivity with other bacteria included in the study, and had an analytical sensitivity of 1 CFU. Of 192 clinical specimens that were positive for N. gonorrhoeae according to the COBAS AMPLICOR assay, 42 were confirmed as positive using the 16S rRNA gene target, 26 were confirmed using the cppB target, and 30 were confirmed using the gyr target. It was concluded that the real-time PCR assay targeting the 16S rRNA gene is a useful confirmatory assay to complement the COBAS AMPLICOR screening test for N. gonorrhoeae.

Epidemiological characteristics of reported sporadic and outbreak cases of E. coli O157 in people from Alberta, Canada (2000-2002): methodological challenges of comparing clustered to unclustered data.

Using multivariable models, we compared whether there were significant differences between reported outbreak and sporadic cases in terms of their sex, age, and mode and site of disease transmission. We also determined the potential role of administrative, temporal, and spatial factors within these models. We compared a variety of approaches to account for clustering of cases in outbreaks including weighted logistic regression, random effects models, general estimating equations, robust variance estimates, and the random selection of one case from each outbreak. Age and mode of transmission were the only epidemiologically and statistically significant covariates in our final models using the above approaches. Weighing observations in a logistic regression model by the inverse of their outbreak size appeared to be a relatively robust and valid means for modelling these data. Some analytical techniques, designed to account for clustering, had difficulty converging or producing realistic measures of association.

Staphylococcus aureus bacteremia in patients receiving pegylated interferon-alpha and ribavirin for chronic hepatitis C virus infection.

Bacteremia has rarely been reported in patients receiving treatment for hepatitis C virus (HCV) infection. We describe the features and investigation of four cases of Staphylococcus aureus bacteremia occurring between 3 November 2004 and 10 January 2005 in patients on therapy for chronic HCV infection. The unusual occurrence of S. aureus bacteremia in a series of patients led to an epidemiologic investigation and molecular typing methods were employed to assess the relatedness of cases. The mean time of bacteremia onset was week 10 of HCV treatment. No patient had neutropenia previously. The average duration of bacteremia was 2.6 days and complications included acute renal failure (2/4), disseminated intravascular coagulopathy (DIC) with sepsis syndrome (1/4), septic arthritis (1/4), spinal epidural abscess (1/4) and endocarditis (1/4). Two patients were in the same weight class for dosing, but no other epidemiologic links were found. One patient admitted to intravenous drug use (IVDU) and a second was suspected of IVDU. The two other patients were cirrhotic, but had no further identifiable risk factors. All bacterial isolates were methicillin-susceptible. By pulsed-field gel electrophoresis, two cases were found to have identical bacterial strains. However, fluorescent-based amplified fragment-length polymorphism analysis demonstrated distinct band patterns in all four cases. The epidemiologic data and molecular analysis of this cluster of S. aureus bacteremia cases among patients receiving combination therapy for treatment of chronic HCV infection suggest that these cases were not related. Additionally, IVDU and cirrhosis, but not neutropenia, are identified as potential risk factors for this uncommon complication of HCV therapy.