No abstract

Salmonellosis is a global problem caused by the international movement of foods and high incidence in exporting countries. In September 2001, in an outbreak investigation Australia isolated Salmonella Stanley from imported peanuts, which resulted in a wider investigation in Canada, England & Wales and Scotland. Patients infected with Salmonella serotypes known to be isolated from peanuts and reported to surveillance systems were interviewed to determine exposure histories. Tagged image file format (TIFF) images of pulsed-field gel electrophoresis (PFGE) patterns of Salmonella isolates were shared electronically amongst laboratories. Laboratories tested packets of 'Brand X' peanuts from various lots and product lines. In total, 97 cases of S. Stanley and 12 cases of S. Newport infection were found. Seventy-three per cent (71/97) of S. Stanley cases were in persons of Asian ethnicity. Twenty-eight per cent of cases recalled eating Brand X peanuts and a further 13% had peanuts in their house in the previous month or had eaten Asian-style peanuts. Laboratories isolated S. Stanley, S. Newport, S. Kottbus, S. Lexington and S. Unnamed from Brand X peanuts. Isolates of S. Stanley from peanuts and human patients were indistinguishable by PFGE. This international outbreak resulted from a product originating from one country affecting several others. Rapid sharing of electronic DNA images was a crucial factor in delineating the outbreak; multinational investigations would benefit from a harmonized approach.

Food poisoning laboratories identify Bacillus cereus using routine methods that may not differentiate all Bacillus cereus group species. We recharacterized Bacillus food-poisoning strains from 39 outbreaks and identified B. cereus in 23 outbreaks, B. thuringiensis in 4, B. mycoides in 1, and mixed strains of Bacillus in 11 outbreaks. (16,19,22). They are difficult to discern using standard biochemical schemes, chemotaxonomic methods, or phylogenetically relevant target genes (1, 2), and many distinguishing pathogenicity markers in this group can be attributed to mobile plasmids (18,21,22,23). B. cereus sensu stricto carries the plasmid-borne emetic toxin cereulide (ces) (7,13,14), and B. thuringiensis carries insecticidal crystal protein (ICP) (cry) genes on one or more plasmids (3, 5, 6). The differentiation of B. cereus group members using molecular techniques is not routine in food-poisoning diagnostic methods and may cause underreporting of species such as B. thuringiensis (1,8 DNA was extracted by lysing pure culture in a heating block at 102°C for 10 min. Microcentrifuged supernatant was frozen at Ϫ80°C until required. Pathogenicity genes for emetic cereulide toxin (nonribosomal peptide synthetase [NRPS]) and ICP (cry1 or cry2) were detected in multiplex PCR assays (7, 10) shown in Fig. 1. Each master mix contained 0.8 M of each primer, hot start master mix, diethyl pyrocarbonate water (20 l), and 5 l of DNA. The PCR products were loaded onto 2% agarose gels made with 0.5ϫ Tris-borate-EDTA buffer and ethidium bromide (1 g ml Ϫ1 ). The gels were electrophoresed at 120 V for 30 min and then visualized on a Bio-Rad Gel Doc 2000.Strains positive for NRPS were designated as B. cereus, those positive for ICP (by microscopy or PCR) as B. thuringiensis, those with rhizoidal growth on nutrient agar as B. mycoides, and all other strains with the typical B. cereus phenotype as B. cereus NRPS Ϫ ICP Ϫ . PCR-negative isolates were further examined for ICP crystals using transmission electron microscopy (TEM) since B. thuringiensis strains may carry one to six cry genes and there is no universal method available to detect all cry genes (there are currently more than 150 cry1 toxins) (17; Bacillus thuringiensis toxin nomenclature [http: //www.lifesci.sussex.ac.uk/Home/Neil_Crickmore/Bt/]). Samples of B. cereus group bacteria were prepared for electron microscopy by fixation with 2% glutaraldehyde and 1% para-

In 2011, a Diarrhetic Shellfish Poisoning (DSP) outbreak occurred in British Columbia (BC), Canada that was associated with cooked mussel consumption. This is the first reported DSP outbreak in BC. Investigation of ill individuals, traceback of product and laboratory testing for toxins were used in this investigation. Sixty-two illnesses were reported. Public health and food safety investigation identified a common food source and harvest area. Public health and regulatory agencies took actions to recall product and notify the public. Shellfish monitoring program changes were implemented after the outbreak. Improved response and understanding of toxin production will improve management of future DSP outbreaks.

Soft ripened cheese (SRC) caused over 130 foodborne illnesses in British Columbia (BC), Canada, during two separate listeriosis outbreaks. Multiple agencies investigated the events that lead to cheese contamination with Listeria monocytogenes (L.m.), an environmentally ubiquitous foodborne pathogen. In both outbreaks pasteurized milk and the pasteurization process were ruled out as sources of contamination. In outbreak A, environmental transmission of L.m. likely occurred from farm animals to personnel to culture solutions used during cheese production. In outbreak B, birds were identified as likely contaminating the dairy plant's water supply and cheese during the curd-washing step. Issues noted during outbreak A included the risks of operating a dairy plant in a farm environment, potential for transfer of L.m. from the farm environment to the plant via shared toilet facilities, failure to clean and sanitize culture spray bottles, and cross-contamination during cheese aging. L.m. contamination in outbreak B was traced to wild swallows defecating in the plant's open cistern water reservoir and a multibarrier failure in the water disinfection system. These outbreaks led to enhanced inspection and surveillance of cheese plants, test and release programs for all SRC manufactured in BC, improvements in plant design and prevention programs, and reduced listeriosis incidence.

Salmonella enterica var. Heidelberg was isolated from an unusual food source during routine case follow-up, prompting a case control investigation of frozen chicken nuggets and strips. Most frozen nuggets and strips are raw; however, par-frying lends a cooked appearance. As such, suitable food preparation precautions might not be undertaken by consumers. Cases were confirmed in the laboratory between 1 January and 1 April 2003. Controls were generated through forward-digit dialing and individually matched by age category. Telephone interviews were conducted, and limited sampling of unopened product was performed. Eighteen matched pairs were interviewed. The odds of infection were 11 times higher in individuals who had consumed frozen processed chicken nuggets and strips (95% confidence interval, 1.42 < odds ratio < 85.20). One-third of cases and controls considered frozen nuggets and strips to be precooked, and one quarter used the microwave, an ill-advised cooking method. Consumer misconceptions contributed to the risk of infection. Clear labels identifying nuggets and strips as raw poultry are needed.

There has been a steady increase in illness incidence of Vibrio parahaemolyticus (Vp). The majority of illnesses are associated with consumption of raw oysters. In the summer of 2015, Canada experienced the largest outbreak associated with the consumption of raw oysters harvested from British Columbia (BC) coastal waters. Case investigation of laboratory-confirmed cases was conducted to collect information on exposures and to assist traceback. Investigations at processors and oyster sampling were conducted. Eighty-two laboratory-confirmed cases of Vp infection were reported between January 1 and October 26, 2015. The majority of the cases were reported in BC, associated with consumption of raw BC oysters in restaurants. Sea surface temperatures were above the historical levels in 2015. This outbreak identified the need to improve surveillance and response to increases in human cases of Vp. This is of particular importance due to the potential for increasing water temperatures and the likelihood of additional outbreaks of Vibrio.

This outbreak is unlike most shellfish outbreaks that can be traced back to a common source and challenges conventional thinking that all oyster-related norovirus outbreaks of are a result of point source contamination.