First Report of Bacterial Blight of Crucifers Caused by Pseudomonas cannabina pv. alisalensis in Minnesota on Arugula (Eruca vesicaria subsp. sativa).

In 2011, bacterial blight of arugula (Eruca vesicaria subsp. sativa; cv. Roquette) was observed in organically grown plants under overhead irrigation in a field near Delano, MN. Approximately 80 to 100% of each planting was affected, with greater rates of infection occurring after periods of high humidity. Small, water-soaked, angular spots apparent on both sides of the leaves comprised the initial symptoms, which sometimes expanded and coalesced. Lesions maintained a dark water-soaked appearance or dried and turned a brown/tan color. Additionally, some lesions were outlined by a purple margin. Blue-green fluorescent pseudomonads were isolated consistently on King's Medium B agar (KMB) from symptomatic leaf tissue surface-disinfested with sodium hypochlorite (0.525%). The isolates nucleated ice and produced levan. Isolates were oxidase and arginine dihydrolase negative. They did not rot potato slices but did induce a hypersensitive reaction in tobacco (Nicotiana tabacum cv. Samsun). These data indicated that the bacteria belonged to Lelliott's LOPAT group 1 (2). DNA fragment banding patterns generated by amplifying DNA of the arugula isolates using repetitive extragenic palindromic sequence-polymerase chain reaction (rep-PCR) and the BOX A1R primer were identical and nearly identical to the banding patterns of the Pseudomonas cannabina pv. alisalensis (formerly P. syringae pv. alisalensis) (1) strain (CFBP1637) and the pathotype strain (CFBP 6866PT), respectively. Pathogenicity was confirmed on the arugula cv. My Way in two independent experiments, each with three replicate plants per treatment. Four isolates were grown on KMB for 48 h at 27°C, suspended in 0.01M potassium phosphate buffer (pH 7.0), and adjusted to 0.6 optical density at 600 nm (approximately 1 × 108 CFU/ml). Five- to six-week old plants were spray-inoculated until run-off, incubated in a humidity chamber for 48 h, and then placed in a greenhouse at 20 to 25°C for symptom development. For negative and positive control treatments, a similar number of plants each were sprayed with sterile buffer or P. cannabina pv. alisalensis strains CFBP1637 and CFBP 6866PT, respectively. Water-soaked and brown/tan lesions similar to the original symptoms appeared on plants inoculated with the arugula isolates and P. cannabina pv. alisalensis strains 7 to 14 days postinoculation. No symptoms developed on plants treated with sterile buffer. The bacterial strains re-isolated from surface-disinfested symptomatic tissue were identical by rep-PCR to the isolates used to inoculate the plants, thus, confirming Koch's postulates. Identical replicated experiments conducted on broccoli raab indicated that the arugula isolates were also pathogens of broccoli raab (Brassica rapa subsp. rapa, the original host from which P. cannabina pv. alisalensis was isolated). To our knowledge, this is the first report of bacterial blight of crucifers caused by P. cannabina pv. alisalensis in Minnesota. Arugula germplasm is being evaluated for resistance to this pathogen as an acceptable management method for organic cropping systems. References: (1) C. T. Bull et al. Syst. Appl. Microbiol. 33:105, 2010. (2) R. A. Lelliott. J. Appl. Bacteriol. 29:470, 1966.

Epidemiology of a large restaurant-associated outbreak of Shiga toxin-producing Escherichia coli O111:NM.

In August 2008, a large outbreak of Shiga toxin-producing Escherichia coli (STEC) O111:NM infections associated with a buffet-style restaurant in rural Oklahoma was identified. A case-control study of restaurant patrons and a retrospective cohort study of catered event attendees were conducted coupled with an environmental investigation to determine the outbreak's source and mode of transmission. Of 1823 persons interviewed, 341 (18·7%) met the outbreak case definition; 70 (20·5%) were hospitalized, 25 (7·3%) developed haemolytic uraemic syndrome, and one died. Multiple food items were significantly associated with illness by both bivariate and multivariate analyses, but none stood out as a predominant transmission vehicle. All water, food, and restaurant surface swabs, and stool cultures from nine ill employees were negative for the presence of Shiga toxin and E. coli O111:NM although epidemiological evidence suggested the outbreak resulted from cross-contamination of restaurant food from food preparation equipment or surfaces, or from an unidentified infected food handler.

Development of perfluorocarbon (PFC) primary standards for monitoring of emissions from aluminum production.

An EPA Voluntary Aluminum Industrial Partnership (VAIP) program has been formed to help US primary producers focus on reducing the emissions of two perfluorocarbons (PFCs), tetrafluoromethane (CF4) and hexafluoroethane (C2F6), during the production of aluminum. To ensure comparability of measurements over space and time, traceability to national sources was desirable. Hence, the EPA approached the NIST to develop a suite of primary standards to cover a mole fraction (concentration) range of 0.1 to 1400 micromol mol(-1) for CF4 and 0.01 to 150 micromol mol(-1) of C2F6. A total of eight gravimetric PFC gas standards were prepared with relative expanded uncertainties of < or = 0.52% (approximately 95% confidence level). These primary standards were ultimately used to assign values to a series of secondary gas standards at three mole-fraction levels with relative expanded uncertainties ranging from +/- 0.7% to 5.3% (approximately 95% confidence level). This series of secondary standards was used within the aluminum industry to calibrate instruments used to make emission measurements. Assignment of values to the secondary standards was performed by use of gas chromatography with flame-ionization detection (GC-FID) and Fourier transform infrared spectrometry (FTIR). Real time pot-line and stack samples from a local aluminum plant were also obtained and sub-samples sent to each participating facility for analysis. The data generated from each facility were sent to NIST for analysis. The maximum difference between the NIST and individual facilities' values for the same sub-sample was +/- 26%.

Francisella tularensis strain typing using multiple-locus, variable-number tandem repeat analysis.

Francisella tularensis, the etiological agent of tularemia, is found throughout the Northern hemisphere. After analyzing the F. tularensis genomic sequence for potential variable-number tandem repeats (VNTRs), we developed a multilocus VNTR analysis (MLVA) typing system for this pathogen. Variation was detected at six VNTR loci in a set of 56 isolates from California, Oklahoma, Arizona, and Oregon and the F. tularensis live vaccine strain. PCR assays revealed diversity at these loci with total allele numbers ranging from 2 to 20, and Nei's diversity index values ranging from 0.36 to 0.93. Cluster analysis identified two genetically distinct groups consistent with the current biovar classification system of F. tularensis. These findings suggest that these VNTR markers are useful for identifying F. tularensis isolates at this taxonomic level. In this study, biovar B isolates were less diverse than those in biovar A, possibly reflecting the history of tularemia in North America. Seven isolates from a recent epizootic in Maricopa County, Ariz., were identical at all VNTR marker loci. Their identity, even at a hypervariable VNTR locus, indicates a common source of infection. This demonstrates the applicability of MLVA for rapid characterization and identification of outbreak isolates. Future construction of reference databases will allow faster outbreak tracking as well as providing a foundation for deciphering global genetic relationships.

A follow-up comparison of study participants and refusers within a rural elderly population.

BACKGROUND: Survey rates are known to decline with age. Survey results can be affected by response bias if nonresponders are more, or less, likely than participants to suffer from the condition being studied. For instance, it is possible that older adults with dementia would be less likely to participate in a study of dementing disorders. METHODS: A random sample of a rural U.S. population aged 65+ years yielded 1,422 participants and 912 refusers in addition to others who were ineligible, inaccessible, or untestable. Participants and refusers were compared on age, sex, 5-year mortality, and causes of death suggestive of dementia as listed on death certificates. RESULTS: Compared to participants, refusers were significantly older and more likely to be women, with mortality similar to that of participants at approximately 5-year follow-up. Death certificate data revealed no significant differences in reported causes of death indicating or suggesting dementia. CONCLUSIONS: In this population, those who refused to participate in a dementia survey were not more likely to be ill or demented than those who did participate.

Random versus volunteer selection for a community-based study.

BACKGROUND: Selection methods vary greatly in ease and cost-effectiveness. The effects of selection factors associated with subjects' recruitment into studies can introduce bias and seriously limit the generalizability of results. METHODS: For an epidemiologic study, we recruited an age-stratified random sample of 1,422 community-dwelling individuals aged 65+ years from the voter registration lists in a rural area of southwestern Pennsylvania. The first 1,366 of these were accrued through intensive recruitment efforts; the last 56 of them responded to a single mailing. To increase sample size for future risk factor analyses, we also recruited by direct advertisement a sample of 259 volunteers from the same area. The three groups were compared on selected baseline characteristics and subsequent mortality. RESULTS: The two subgroups of the random sample were not significantly different on any of the variables we examined. Compared to the random sample, in cross-sectional analyses, volunteers were significantly more likely to be women, more educated, and less likely to have used several health and human services. Volunteers also had higher cognitive test scores and Instrumental Activities of Daily Living (IADL) ability. Over 6-8 years (10,861 person-years) of follow-up, volunteers had significantly lower mortality rates than randomly selected subjects. CONCLUSIONS: Health-related studies with populations composed partly or entirely of volunteers should take potential volunteer bias into account when analyzing and interpreting data.

Comparison of methods for enumeration of selected coliforms exposed to ozone.

mT7 medium performed no better than m-Endo medium in enumerating cells of Escherichia coli and Citrobacter freundii exposed to ozone. Also, there was no difference in the plate count of heterotrophic bacteria in ozonated raw water determined on modified Henrici agar or R2A agar. Statistically significant differences were seen between bacteria and the type of water in which they were suspended during ozonation.

Use of nutrient response techniques to assess the effectiveness of chlorination of rapid sand filter gravel.

A direct viable counting method was used to rapidly assess the effectiveness of chlorination of biofilms on rapid sand filter gravel. A total of 50% of the cells were nutrient responsive after exposure to 0.5 mg of chlorine per liter, while this value was 25% after exposure to 25 mg of chlorine per liter. A large variation was seen in the numbers of nutrient-responsive cells on different rocks. More cells attached to the sandblasted side of marbles than to the smooth side, but there was no difference in eight of nine cases in the proportion of survival to chlorination between the two different sides. The effectiveness of chlorination appeared to be influenced by the species of bacterium in the biofilm.