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Listeria monocytogenes is a facultative intracellular pathogen thought to be widely distributed in the environment. We investigated the prevalence and characteristics of L. monocytogenes isolates from surface waters derived from catchments within the South Nation River watershed (Ontario, Canada). This watershed is dominated by urban and rural development, livestock and crop production, and wildlife habitats. From June to November 2005, a total of 314 surface water samples were collected biweekly from 22 discrete sampling sites characterized by various upstream land uses. Presumptive Listeria spp. were isolated using a selective enrichment and isolation procedure, and 75 L. monocytogenes isolates were identified based on colony morphology, hemolytic activity, and amplification of three pathogenicity genes: iap, inlA, and hlyA. Thirty-two of 314 (10%) surface water samples were positive for the presence of L. monocytogenes, but detection ranged between 0 and 27% depending on the sampling date. Isolates belonging to serovar group 1/2a, 3a (50%) and group 4b, 4d, 4e (32%) were dominant. L. monocytogenes populations were resolved into 13 EcoRI ribotypes and 21 ApaI and 21 AscI pulsotypes. These had Simpson indexes of discrimination of up to 0.885. Lineage I-related isolates were dominant (61%) during the summer, whereas lineage II isolates were dominant (77%) in the fall. Isolates were, on average, resistant to 6.1 ؎ 2.1 antibiotics out of 17 tested. Half of the L. monocytogenes isolates exhibited potential virulence linked to the production of a functional internalin A, and some isolates were found to be moderately to highly virulent by in vitro Caco-2 plaque formation assay (up to 28% of entry). There was a statistically significant link between the occurrence of L. monocytogenes and proximity to an upstream dairy farm and degree of cropped land. Our data indicate that L. monocytogenes is widespread in the studied catchments, where it could represent a public health issue related to agricultural land use.Listeria monocytogenes is a gram-positive facultative intracellular pathogen responsible for severe food-borne infections in humans and causes 20 to 50% mortality in susceptible populations, such as newborn children, the elderly, and immunocompromised persons (22,56). This bacterium is thought to be a saprophytic organism living naturally in the plant-soil environment, where it can survive for up to several months, being able to multiply in decaying vegetation but unlikely to multiply in soil (16). In the natural environment, biotic and abiotic factors shown to reduce L. monocytogenes survival are predation, high temperature, UV exposure, and low moisture (12,16,20). Soil texture also influences L. monocytogenes survival, but the availability of inorganic nutrients (nitrogen and phosphorus) does not influence survival (12).A possible agricultural route of human exposure is through the ingestion of uncooked food crops grown in soil irrigated with contaminated water and/or fertilized with Listeria-contaminated manur...

We have used comparative genomic hybridization (CGH) on a full-genome Campylobacter jejuni microarray to examine genome-wide gene conservation patterns among 51 strains isolated from food and clinical sources. These data have been integrated with data from three previous C. jejuni CGH studies to perform a metaanalysis that included 97 strains from the four separate data sets. Although many genes were found to be divergent across multiple strains (n ‫؍‬ 350), many genes (n ‫؍‬ 249) were uniquely variable in single strains. Thus, the strains in each data set comprise strains with a unique genetic diversity not found in the strains in the other data sets. Despite the large increase in the collective number of variable C. jejuni genes (n ‫؍‬ 599) found in the meta-analysis data set, nearly half of these (n ‫؍‬ 276) mapped to previously defined variable loci, and it therefore appears that large regions of the C. jejuni genome are genetically stable. A detailed analysis of the microarray data revealed that divergent genes could be differentiated on the basis of the amplitudes of their differential microarray signals. Of 599 variable genes, 122 could be classified as highly divergent on the basis of CGH data. Nearly all highly divergent genes (117 of 122) had divergent neighbors and showed high levels of intraspecies variability. The approach outlined here has enabled us to distinguish global trends of gene conservation in C. jejuni and has enabled us to define this group of genes as a robust set of variable markers that can become the cornerstone of a new generation of genotyping methods that use genome-wide C. jejuni gene variability data.Campylobacter jejuni is a human pathogen, a commensal inhabitant of many domestic animals, and globally, the most common cause of acute bacterial enteritis (for a review, see reference 31). Two well-established serotyping methods, namely, Penner typing based on heat-stable antigens and Lior typing based on heat-labile antigens, have been in use for more than two decades to study species diversity, to track epidemiological trends, and to determine important epidemiological correlations (15,23). Technical limitations on the production of high-quality typing sera have limited the availability of these reagents. Culturing conditions can affect the expression of serotyping determinants, which affects serotyping results, and several strains are nontypeable (32). Additionally, serotype relatedness is not always indicative of genetic relatedness since members of different serotypes of C. jejuni are genetically related, despite differences in heat-stable antigen expression (16).The need for alternative subtyping schemes has been recognized, leading to the development of a number of different methods based on differences at the DNA level (i.e., genotyping). The techniques used at present range from analysis of polymorphisms in groups of housekeeping genes (multilocus sequence typing [5,26]), amplified fragment length polymorphism analysis (28), restriction fragment length polymorphism analysi...

Background: Recent public attention on drinking water supplies in the aftermath of waterborne infection outbreaks in Walkerton and North Battleford raises questions about safety. We analyzed information on waterborne outbreaks occurring between 1974 and 2001 in order to identify apparent trends, review the current status of monitoring and reporting, and gain a better understanding of the impact of drinking water quality on public health and disease burden. Methods: Data from outbreak investigations, published and unpublished, were categorized by the type of drinking water provider and were assessed to be definitely, probably or possibly waterborne in nature. Results: The final data set consisted of 288 outbreaks of disease linked to a drinking water source. There were 99 outbreaks in public water systems, 138 outbreaks in semi-public systems and 51 outbreaks in private systems. The main known causative agents of waterborne disease outbreaks were (in descending frequency of occurrence) Giardia, Campylobacter, Cryptosporidium, Norwalk-like viruses, Salmonella and hepatitis A virus. Summary: We found that severe weather, close proximity to animal populations, treatment system malfunctions, poor maintenance and treatment practices were associated with the reported disease outbreaks resulting from drinking water supplies. However, issues related to the accuracy, coordination , compatibility and detail of data exist. A systematic and coordinated national surveillance system for comparison purposes, trend identification and policy development is needed so that future waterborne disease outbreaks can be avoided.