Integrated surveillance of Salmonella along the food chain using existing data and resources in British Columbia, Canada

Propidium monoazide real-time PCR amplification for viable Salmonella species and Salmonella Heidelberg in pork

Salmonella enterica serovar Heidelberg causes foodborne infections and is a major threat to the food chain and public health. In this study, we aimed to develop a rapid molecular typing approach to identify Salmonella enterica serovar Heidelberg. Using comparative genomics, four serovar-specific gene fragments were identified, and a real-time polymerase chain reaction (PCR) combined with a propidium monoazide (PMA) pretreatment method was developed for simultaneous detection of viable Salmonella sp. (invA) and Salmonella Heidelberg (SeHA_C3258). The assay showed 100% specificity for all strains tested. The assay was able to distinguish effectively viable or dead cells with the PMA. The detection limit was 2.4 CFU/mL following 6 h of incubation in enrichment Luria-Bertani medium, and the assay could detect 1.7 × 10² CFU/mL in the presence of pork background flora. In artificially contaminated pork, real-time PCR detected inoculum levels of 1.15 CFU/25 g of pork after a 6 h enrichment. Thus, our findings indicated that this comparative genomics approach could be used to screen for serovar-specific fragments and that real-time PCR with PMA was a simple and reliable method for detecting viability of Salmonella species and Salmonella Heidelberg.

Red Seaweeds Sarcodiotheca gaudichaudii and Chondrus crispus down Regulate Virulence Factors of Salmonella Enteritidis and Induce Immune Responses in Caenorhabditis elegans

Red seaweeds are a rich source of unique bioactive compounds and secondary metabolites that are known to improve human and animal health. S. Enteritidis is a broad range host pathogen, which contaminates chicken and poultry products that end into the human food chain. Worldwide, Salmonella outbreaks have become an important economic and public health concern. Moreover, the development of resistance in Salmonella serovars toward multiple drugs highlights the need for alternative control strategies. This study evaluated the antimicrobial property of red seaweeds extracts against Salmonella Enteritidis using the Caenorhabditis elegans infection model. Six red seaweed species were tested for their antimicrobial activity against S. Enteritidis and two, Sarcodiotheca gaudichaudii (SG) and Chondrus crispus (CC), were found to exhibit such properties. Spread plate assay revealed that SG and CC (1%, w/v) significantly reduced the growth of S. Enteritidis. Seaweed water extracts (SWE) of SG and CC, at concentrations from 0.4 to 2 mg/ml, significantly reduced the growth of S. Enteritidis (log CFU 4.5–5.3 and log 5.7–6.0, respectively). However, methanolic extracts of CC and SG did not affect the growth of S. Enteritidis. Addition of SWE (0.2 mg/ml, CC and SG) significantly decreased biofilm formation and reduced the motility of S. Enteritidis. Quantitative real-time PCR analyses showed that SWE (CC and SG) suppressed the expression of quorum sensing gene sdiA and of Salmonella Pathogenesis Island-1 (SPI-1) associated genes sipA and invF, indicating that SWE might reduce the invasion of S. Enteritidis in the host by attenuating virulence factors. Furthermore, CC and SG water extracts significantly improved the survival of infected C. elegans by impairing the ability of S. Enteritidis to colonize the digestive tract of the nematode and by enhancing the expression of C. elegans immune responsive genes. As the innate immune response pathways of C. elegans and mammals show a high degree of conservation, these results suggest that these SWE may also impart beneficial effects on animal and human health.

Utility of algorithms for the analysis of integratedSalmonellasurveillance data

The objective of this study was to assess the use of statistical algorithms in identifying significant clusters ofSalmonellaspp. across different sectors of the food chain within an integrated surveillance programme. Three years of weeklySalmonellaserotype data from farm animals, meat, and humans were used to create baseline models (first two years) and identify weeks with counts higher than expected using surveillance algorithms in the third (test) year. During the test year, an expert working group identified events of interest reviewing descriptive analyses of same data. The algorithms did not identifySalmonellaevents presenting as gradual increases or seasonal patterns as identified by the working group. However, the algorithms did identify clusters for further investigation, suggesting they could be a valuable complementary tool within an integrated surveillance system.

Zoonotic disease surveillance--inventory of systems integrating human and animal disease information

Although 65% of recent major disease outbreaks throughout the world have a zoonotic origin, there is still a sharp division among the disciplines into the human and animal health sectors. In the last few decades, a global integrative concept, often referred to as 'One Health', has been strongly endorsed. Surveillance and monitoring efforts are major components for effective disease prevention and control. As human health and animal health are inextricably linked, it is assumed that a cross-sectoral data interpretation of zoonotic disease information will improve their prevention, prediction and control. To provide an overview of existing systems throughout the world which integrate information from humans and animals on zoonotic diseases, a literature review was conducted. Twenty projects were identified and described regarding their concepts and realization. They all vary widely depending on their surveillance purpose, their structure and the source of information they use. What they have in common is that they quite often use data which have already been collected for another purpose. Therefore, the challenges of how to make use of such secondary data are of great interest.

A Canadian application of one health: integration of Salmonella data from various Canadian surveillance programs (2005-2010)

Most bacterial pathogens associated with human enteric illness have zoonotic origins and can be transmitted directly from animals to people or indirectly through food and water. This multitude of potential exposure routes and sources makes the epidemiology of these infectious agents complex. To better understand these illnesses and identify solutions to reduce human disease, an integrative approach like One Health is needed. This article considers the issue of Salmonella in Canada and interprets data collected by several Canadian surveillance and research programs. We describe recovery of Salmonella from various samples collected along the exposure pathway and compare the serovars detected in the different components under surveillance (animal, food, environment, and human). We then present three examples to illustrate how an approach that interprets multiple sources of surveillance data together is able to address issues that transcend multiple departments and jurisdictions. First, differences observed in recovery of Salmonella from different cuts of fresh chicken collected by different programs emphasize the importance of considering the surveillance objectives and how they may influence the information that is generated. Second, the high number of Salmonella Enteritidis cases in Canada is used to illustrate the importance of ongoing, concurrent surveillance of human cases and exposure sources to information domestic control and prevention strategies. Finally, changing patterns in the occurrence of ceftiofur-resistant Salmonella Heidelberg in retail meats and humans demonstrates how integrated surveillance can identify an issue in an exposure source and link it to a trend in human disease. Taken together, surveillance models that encompass different scales can leverage infrastructure, costs, and benefits and generate a multidimensional picture that can better inform disease prevention and control programs.