Changes in the recovery of insects in pitfall traps associated with the age of cow dung bait fresh or frozen at the time of placement.

Pitfall traps baited with cattle dung are commonly used to characterize local assemblages of coprophilous insects. Baits can be made fresh or be prepared in advance and kept frozen until needed. Insect recoveries are expected to decline with the age of the bait and may be affected by the use of fresh vs.

Reaction of Surrogate Serotype O157:H7 and Non-O157 Strains to Nutrient Starvation: Variation in Phenotype and Transcription of Stress Response Genes and Behavior on Lettuce Plants in the Field.

Preharvest contamination with bacteria borne by irrigation water may result in leafy vegetables serving as vehicles for transmission of Shiga toxin-producing (STEC) to humans. The influence of starvation-associated stress on the behavior of non-toxin-producing strains of serotype O157:H7 and serotypes O26, O103, O111, and O145 was examined subsequent to their introduction to the phyllosphere of field-grown romaine lettuce as inocula simulating starved (96 h in sterile deionized water) and nutrient-depleted (24 h broth culture) cells. As with O157:H7, leaf populations of the non-O157 strains declined rapidly during the first 72 h postinoculation, displaying the biphasic decay curve typical of serotype O157:H7 isolates.

Impact of Listeria Inoculation and Aerated Steam Sanitization on Volatile Emissions of Whole Fresh Cantaloupes.

Unlabelled: Rapid methods to detect bacterial pathogens on food and strategies to control them are needed to mitigate consumer risk. This study assessed volatile emissions from whole cantaloupe melons (Cucumis melo) as an indicator of Listeria contamination and in response to steam vapor decontamination. Cantaloupe were inoculated with Listeria innocua, a nonpathogenic surrogate for L.

Aerated Steam Sanitization of Whole Fresh Cantaloupes Reduces and Controls Rind-Associated Listeria but Enhances Fruit Susceptibility to Secondary Colonization.

Unlabelled: Recent bacterial illnesses and outbreaks associated with the consumption of fresh and fresh-cut fruit and vegetables emphasize the need to supply produce that is microbiologically safe while retaining its quality and nutrient value. We assessed the capacity of aerated steam to reduce initial levels and control the posttreatment proliferation of a 4-strain mixture of Listeria innocua, a surrogate for L. monocytogenes, and microflora native to the rind of whole cantaloupes.

Effect of hillslope position and manure application rates on the persistence of fecal source tracking indicators in an agricultural soil.

The influence of liquid dairy manure (LDM) application rates (12.5 and 25 kL ha) and soil type on the decay rates of library-independent fecal source tracking markers (host-associated and mitochondrial DNA) and persistent (>58 d) population structure was examined in a field study. The soils compared were an Aquic Haplorthod and a Typic Haplorthod in Nova Scotia, Canada, that differed according to landscape position and soil moisture regime.

Reach specificity in sediment E. coli population turnover and interaction with waterborne populations.

Sediment-borne Escherichia coli can elevate waterborne concentrations through sediment resuspension or hyporheic exchange. This study sought to correlate hydrological, sediment transport, and water quality variables with: (i) the temporal stability of sediment E. coli populations [concentrations, strain richness and similarity (Raup-Crick index)]; and (ii) the contribution of sediment E.

Baseline and storm event monitoring of Bacteroidales marker concentrations and enteric pathogen presence in a rural Canadian watershed.

Bacteroidales 16S rRNA gene markers were evaluated for their use as a microbial source tracking tool in a well characterized 750 ha agricultural watershed in Nova Scotia, Canada. Water quality monitoring was conducted following the validation of host-specific and universal Bacteroidales (AllBac) markers for their proficiency in this particular geographic region, which provided further evidence that these markers are geographically stable. Increasing Escherichia coli concentrations were positively correlated (p < 0.

Evaluation of different approaches for modeling Escherichia coli O157:H7 survival on field lettuce.

The ability to predict the behavior of Escherichia coli O157:H7 on contaminated field lettuce is essential for the development of accurate quantitative microbial risk assessments. The survival pattern of the species was assessed from several data sets derived from field-based experiments, which were analyzed by regression analysis fitting one monophasic model (log-linear) and two biphasic (Weibull and Cerf's model) models. Probabilistic models were also simulated with @RISK™, integrating the fitted monophasic and biphasic models in order to analyze their impact on the estimate of the extent of die-off subsequent to a contamination event in the field.

Evaluation of statistical models for predicting Escherichia coli particle attachment in fluvial systems.

Modeling surface water Escherichia coli fate and transport requires partitioning E. coli into particle-attached and unattached fractions. Attachment is often assumed to be a constant fraction or is estimated using simple linear models.

Characterizing spatial structure of sediment E. coli populations to inform sampling design.

Escherichia coli can persist in streambed sediments and influence water quality monitoring programs through their resuspension into overlying waters. This study examined the spatial patterns in E. coli concentration and population structure within streambed morphological features during baseflow and following stormflow to inform sampling strategies for representative characterization of E.

Comparative examination of Escherichia coli O157:H7 survival on romaine lettuce and in soil at two independent experimental sites.

Little is known about the influence of abiotic factors such as climate and soil chemistry on the survival of Escherichia coli O157:H7 in field lettuce. We applied a nalidixic acid-resistant derivative of strain ATCC 700728 to field-grown romaine lettuce in two regions in Canada characterized by large variances in soil type and climate. Surviving populations in soil and on lettuce leaves were estimated on sorbitol MacConkey agar supplemented with nalidixic acid.

Population dynamics of Escherichia coli inoculated by irrigation into the phyllosphere of spinach grown under commercial production conditions.

Recent outbreaks of food-borne illnesses associated with the consumption of fresh produce have increased attention on irrigation water as a potential source of pathogen contamination. A better understanding of the behaviour of enteric pathogens introduced into agricultural systems during irrigation will aid in risk assessments and support the development of appropriate farm-level water management practices. For this reason, the survival dynamics of two nalidixic acid resistant strains of Escherichia coli after their spray inoculation into the phyllosphere and soil of field spinach were examined over two growing seasons.

Presence and potential for horizontal transfer of antibiotic resistance in oxidase-positive bacteria populating raw salad vegetables.

To assess whether domestically grown fresh salad vegetables constitute a possible reservoir of antibiotic resistance for Canadian consumers, aerobic bacteria capable of forming colonies at 30 degrees C on nutrient-limited media were recovered from a single sampling of Romaine lettuce, Savoy spinach and alfalfa sprouts, then examined for their susceptibility to ten antibiotics and the carriage of potentially mobile R-plasmids and integrons. Of the 140 isolates resistant to one or more antibiotic, 93.5 and 90.

Analysis of Legionella pneumophila serogroup 1 isolates by pulsed-field gel electrophoresis.

At a hospital in Halifax, Nova Scotia, Canada, three strains of Legionella pneumophila were detectable based on plasmid content, while the isolates collected at another hospital in Halifax had no plasmids. Genomic DNA was digested with BssHII, SalI, and SpeI and subjected to pulsed-field gel electrophoresis (PFGE). We found no relationship between plasmid profile and PFGE pattern.

Helicobacter pylori: primary susceptibility to clarithromycin in vitro in Nova Scotia.

Resistance to antimicrobial agents is a major determinant of the efficacy of regimens to eradicate Helicobacter pylori. Clarithromycin (CLA) has become one of the most commonly used antibiotics for treatment of H pylori infection. In this study, the rate of primary resistance to CLA in H pylori isolated from patients was determined.

Characterization and cloning of a 37.6-kb plasmid carried by Legionella pneumophila recovered from patients and hospital water over a 12-year period.

For 12 years, strains of Legionella pneumophila serogroup 1 harbouring a 37.6-kb (23 MDa) plasmid have predominated among patient and potable water isolates at the Victoria General Hospital, Halifax, N.S.

Potable water and nosocomial Legionnaires' disease--check water from all rooms in which patient has stayed.

We studied 7 patients with nosocomial Legionnaires' disease to determine the relationship between isolates of Legionella pneumophila recovered from potable water and those recovered from patients. Potable water was cultured from all rooms in which patients had stayed prior to the diagnosis of Legionnaires' disease. The 38 isolates of L.

Genomic stability of Legionella pneumophila isolates recovered from two cardiac transplant patients with nosocomial Legionnaires' disease.

Pulsed-field gel electrophoresis revealed that multiple consecutive isolates of Legionella pneumophila from two cardiac transplant patients remained genomically stable, despite exposure to host defenses and antimicrobial agents.

Virulence of patient and water isolates of Legionella pneumophila in guinea pigs and mouse L929 cells varies with bacterial genotype.

Thirteen isolates of Legionella pneumophila serogroup 1 (five from patients, eight from water) were screened for their virulence in guinea pigs after intraperitoneal injection and for their infectivity in L929 mouse cells. Since these isolates included three monoclonal antibody subtypes and four genotypes, the relative influence of these parameters on the pathogenicity of naturally occurring L. pneumophila could be assessed.

Serological detection of Helicobacter pylori antibodies in children and their parents.

The antibody response to Helicobacter pylori was examined in 56 children (ages 5 to 18) to determine whether serological tests can be used for diagnosis. Twenty-four children (43%) were H. pylori positive and 32 children (57%) were H.

Legionellaceae in the potable water of Nova Scotia hospitals and Halifax residences.

Water was cultured from 39 of 48 hospitals (7 Halifax hospitals and 32 non-Halifax hospitals) in the province of Nova Scotia and from 90 residences (74 private dwellings, 16 apartments) in Halifax to determine the frequency of legionella contamination. Six of seven Halifax hospitals had Legionellaceae isolated from their potable water compared with 3 of 32 non-Halifax hospitals (P < 0.0001).

Increasing prevalence of Helicobacter pylori infection with age: continuous risk of infection in adults rather than cohort effect.

It remains unclear whether acquisition of Helicobacter pylori is due to a continuous risk of acquiring the infection or a cohort effect. In this prospective 3-year cohort study, the seroprevalence, conversion, and reversion of H. pylori infection as determined by IgG antibodies was examined.

Nosocomial Legionnaires' disease: Clinical and radiographic patterns.

From 1981 to 1991, 55 patients (33 males, 22 females, mean age 58.6 years) with nosocomial Legionnaires' disease were studied. The mortality rate was 64%.

Serological detection of Helicobacter pylori by a flow microsphere immunofluorescence assay.

A flow cytometric immunofluorescence assay (FMIA) for the detection of immunoglobulin G antibodies to Helicobacter pylori was developed. A multicomponent antigen was prepared and used to coat carboxylated polystyrene microspheres for reaction with patient sera followed by fluorescein isothiocyanate-labelled goat anti-human immunoglobulin G. The reacted microspheres were collected with a flow cytometer, and fluorescence was quantitated relative to the cutoff value provided by pooled sera from patients in whom H.