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Laidler M.R.,Acute and Communicable Disease Prevention | Tourdjman M.,Acute and Communicable Disease Prevention | Tourdjman M.,Centers for Disease Control and Prevention | Buser G.L.,Acute and Communicable Disease Prevention | And 6 more authors.
Clinical Infectious Diseases | Year: 2013

Background. An outbreak of Escherichia coli O157:H7 was identified in Oregon through an increase in Shiga toxin-producing E. coli cases with an indistinguishable, novel pulsed-field gel electrophoresis (PFGE) subtyping pattern.Methods. We defined confirmed cases as persons from whom E. coli O157:H7 with the outbreak PFGE pattern was cultured during July-August 2011, and presumptive cases as persons having a household relationship with a case testing positive for E. coli O157:H7 and coincident diarrheal illness. We conducted an investigation that included structured hypothesis-generating interviews, a matched case-control study, and environmental and traceback investigations. Results. We identified 15 cases. Six cases were hospitalized, including 4 with hemolytic uremic syndrome (HUS). Two cases with HUS died. Illness was significantly associated with strawberry consumption from roadside stands or farmers' markets (matched odds ratio, 19.6; 95% confidence interval, 2.9-∞). A single farm was identified as the source of contaminated strawberries. Ten of 111 (9%) initial environmental samples from farm A were positive for E. coli O157:H7. All samples testing positive for E. coli O157:H7 contained deer feces, and 5 tested farm fields had ≥1 sample positive with the outbreak PFGE pattern.Conclusions. The investigation identified fresh strawberries as a novel vehicle for E. coli O157:H7 infection, implicated deer feces as the source of contamination, and highlights problems concerning produce contamination by wildlife and regulatory exemptions for locally grown produce. A comprehensive hypothesis-generating questionnaire enabled rapid identification of the implicated product. Good agricultural practices are key barriers to wildlife fecal contamination of produce. © 2013 The Author 2013. Published by Oxford University Press on behalf of the Infectious Diseases Society of America. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Green H.C.,Oregon State University | Dick L.K.,Ohio State University | Gilpin B.,Institute of Environmental Science and Research | Samadpour M.,Institute for Environmental Health | Field K.G.,Oregon State University
Applied and Environmental Microbiology | Year: 2012

Avian feces contaminate waterways but contribute fewer human pathogens than human sources. Rapid identification and quantification of avian contamination would therefore be useful to prevent overestimation of human health risk. We used subtractive hybridization of PCR-amplified gull fecal 16S RNA genes to identify avian-specific fecal rRNA gene sequences. The subtracters were rRNA genes amplified from human, dog, cat, cow, and pig feces. Recovered sequences were related to Enterobacteriaceae (47%), Helicobacter (26%), Catellicoccus (11%), Fusobacterium (11%), and Campylobacter (5%). Three PCR assays, designated GFB, GFC, and GFD, were based on recovered sequence fragments. Quantitative PCR assays for GFC and GFD were developed using SYBR green. GFC detected down to 0.1 mg gull feces/100 ml (corresponding to 2 gull enterococci most probable number [MPN]/100 ml). GFD detected down to 0.1 mg chicken feces/100 ml (corresponding to 13 Escherichia coli MPN/100 ml). GFB and GFC were 97% and 94% specific to gulls, respectively. GFC cross-reacted with 35% of sheep samples but occurred at about 100,000 times lower concentrations in sheep. GFD was 100% avian specific and occurred in gulls, geese, chickens, and ducks. In the United States, Canada, and New Zealand, the three markers differed in their geographic distributions but were found across the range tested. These assays detected four important bird groups contributing to fecal contamination of waterways: gulls, geese, ducks, and chickens. Marker distributions across North America and in New Zealand suggest that they will have broad applicability in other parts of the world as well. © 2012, American Society for Microbiology.

Churi A.,Texas A&M University | Churi A.,Institute for Environmental Health | Chalova V.I.,Texas A&M University | Chalova V.I.,University of Arkansas | And 5 more authors.
Food Biotechnology | Year: 2010

Entry of a pathogen into a warm-blooded host can be accompanied by an increase in temperature. Therefore, it is expected that heat shock genes could play an important role in bacterial infection. The gene hilA encodes for a transcriptional regulator and is essential for S. Typhimurium invasion. In the current study, we generated a transcriptional fusion between the promoter of hilA and the gene gfp[LVA] encoding for a mutant GFP with a half-life of 40 min to observe the effect of heat as a stressor in activating hilA in Salmonella. β-galactosidase assays were also conducted to verify the expression of hilA under the investigated conditions. The highest induction of hilA (3.38 fold) was observed after 1 h of heat treatment (45°C) as measured by the hilA-gfp[LVA] fusion construct. The cell transfer back to 37°C resulted in a gradual decrease in hilA expression and no detectable induction after 2 h. Based on the activity of β-galactosidase, heat treatment of S. Typhimurium hilA::lacZY fusion strain at 45 oC was found to induce the expression of hilA 1.56 fold. The data demonstrates that elevated temperature may be an inducer of hilA expression. More studies including broader range of temperatures and conditions are needed to better characterize the influence of temperature increases on Salmonella pathogenicity. © Taylor & Francis Group, LLC.

Oyarzabal O.A.,Institute for Environmental Health | Williams A.,Alabama State University | Zhou P.,Alabama State University | Samadpour M.,Institute for Environmental Health
Journal of Microbiological Methods | Year: 2013

To improve the detection of Campylobacter spp. in retail broiler meat, a reference method (R subsamples) based on the enrichment of 25. g of meat in Bolton broth at 42. °C under microaerobiosis was compared with an alternative method (A subsamples) consisting in the rinsing of meat samples for 30. s in buffered peptone water with antimicrobials with incubation at 42. °C under aerobiosis. One piece of meat (breasts, tenderloins and thighs) was rinse in experiment 1 (A1) and two pieces in experiment 2 (A2). Campylobacter spp. were isolated on agar plates and identified by PCR. Retail samples in Alabama had less prevalence (P≤. 0.05) than samples in the state of Washington. The percentage of positive was higher (P≤. 0.05) in A than in R subsamples and rinsing two pieces of meat yielded the highest percentage of positive subsamples. R subsamples showed variations in the prevalence by product. However, A subsamples had similar prevalence of positives among products compare to the result from reference method. More Campylobacter coli isolates were collected in A2 subsamples. Pulse field gel electrophoresis (PFGE) was used as subtyping method to study the genome similarity among the isolates from all methods. A larger diversity of isolates were detected by PFGE in A2 subsamples. Denaturing gradient gel electrophoresis analysis suggested that the initial bacterial populations of the meat samples impact the final bacterial profile after enrichment. Rinsing broiler meats was less time consuming, required less sample preparation and was more sensitive than the reference method for the isolation of naturally occurring Campylobacter spp. This new method could help with epidemiological and intervention studies to control Campylobacter spp. © 2013 Elsevier B.V.

Kisiela D.I.,University of Washington | Chattopadhyay S.,University of Washington | Libby S.J.,University of Washington | Karlinsey J.E.,University of Washington | And 11 more authors.
PLoS Pathogens | Year: 2012

Whereas the majority of pathogenic Salmonella serovars are capable of infecting many different animal species, typically producing a self-limited gastroenteritis, serovars with narrow host-specificity exhibit increased virulence and their infections frequently result in fatal systemic diseases. In our study, a genetic and functional analysis of the mannose-specific type 1 fimbrial adhesin FimH from a variety of serovars of Salmonella enterica revealed that specific mutant variants of FimH are common in host-adapted (systemically invasive) serovars. We have found that while the low-binding shear-dependent phenotype of the adhesin is preserved in broad host-range (usually systemically non-invasive) Salmonella, the majority of host-adapted serovars express FimH variants with one of two alternative phenotypes: a significantly increased binding to mannose (as in S. Typhi, S. Paratyphi C, S. Dublin and some isolates of S. Choleraesuis), or complete loss of the mannose-binding activity (as in S. Paratyphi B, S. Choleraesuis and S. Gallinarum). The functional diversification of FimH in host-adapted Salmonella results from recently acquired structural mutations. Many of the mutations are of a convergent nature indicative of strong positive selection. The high-binding phenotype of FimH that leads to increased bacterial adhesiveness to and invasiveness of epithelial cells and macrophages usually precedes acquisition of the non-binding phenotype. Collectively these observations suggest that activation or inactivation of mannose-specific adhesive properties in different systemically invasive serovars of Salmonella reflects their dynamic trajectories of adaptation to a life style in specific hosts. In conclusion, our study demonstrates that point mutations are the target of positive selection and, in addition to horizontal gene transfer and genome degradation events, can contribute to the differential pathoadaptive evolution of Salmonella. © 2012 Kisiela et al.

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