Cardiovascular disease after Escherichia coli O157:H7 gastroenteritis

Background:

Escherichia coli O157:H7 is one cause of acute bacterial gastroenteritis, which can be devastating in outbreak situations. We studied the risk of cardiovascular disease following such an outbreak in Walkerton, Ontario, in May 2000.

Methods:

In this community-based cohort study, we linked data from the Walkerton Health Study (2002–2008) to Ontario’s large healthcare databases. We included 4 groups of adults: 3 groups of Walkerton participants (153 with severe gastroenteritis, 414 with mild gastroenteritis, 331 with no gastroenteritis) and a group of 11 263 residents from the surrounding communities that were unaffected by the outbreak. The primary outcome was a composite of death or first major cardiovascular event (admission to hospital for acute myocardial infarction, stroke or congestive heart failure, or evidence of associated procedures). The secondary outcome was first major cardiovascular event censored for death. Adults were followed for an average of 7.4 years.

Results:

During the study period, 1174 adults (9.7%) died or experienced a major cardiovascular event. Compared with residents of the surrounding communities, the risk of death or cardiovascular event was not elevated among Walkerton participants with severe or mild gastroenteritis (hazard ratio [HR] for severe gastroenteritis 0.74, 95% confidence interval [CI] 0.38–1.43, mild gastroenteritis HR 0.64, 95% CI 0.42–0.98). Compared with Walkerton participants who had no gastroenteritis, risk of death or cardiovascular event was not elevated among participants with severe or mild gastroenteritis.

Interpretation:

There was no increase in the risk of cardiovascular disease in the decade following acute infection during a major E. coli O157:H7 outbreak.Escherichia coli O157:H7 is one cause of acute bacterial gastroenteritis, causing 63 000 infections each year and 12 major outbreaks since 2006 in the United States alone.^1,2 This strain was most recently implicated in the outbreak involving beef from XL Foods (September 2012), with 17 confirmed cases across Canada.³ A similar enterohemorrhagic strain E. coli O104:H4 was responsible for an outbreak in Germany in May 2011, causing 3792 cases of gastroenteritis and 43 deaths.^4,5Most patients fully recover from acute gastroenteritis caused by E. coli. However, such an illness may predispose patients to long-term disease. Shiga toxin is produced by E. coli O157:H7; this toxin damages the microvasculature of the kidneys leading to hypertension^6–13 and directly damages the systemic vasculature.^14–16 Infected people may progress from a state of acute inflammation of the vasculature to subclinical chronic inflammation, which could promote atherosclerosis.^17–20In Walkerton, Ontario, in May 2000, heavy rains transported bovine fecal matter into the town’s well, contaminating the inadequately chlorinated municipal water supply with E. coli O157:H7.²¹ Over 2300 people developed acute gastroenteritis, and 7 people died.²² The unique circumstances of this outbreak provided a rare opportunity to study the natural history following exposure to this pathogen in a single cohort.²³ Other outbreaks have been geographically dispersed, making it difficult to track cases.^24,25In Walkerton, affected individuals were followed annually in a clinic to assess their long-term outcomes (Walkerton Health Study, 2002–2008). We previously reported that adults who experienced acute gastroenteritis during the outbreak had a higher than expected incidence of hypertension, chronic kidney disease and self-reported cardiovascular disease in follow-up.²³ However, 46% of participants were lost to follow-up by the end of the study, and there were limitations associated with the assessment of cardiovascular disease by participant recall. Thus, we conducted an expanded and extended follow-up study, linking the Walkerton study data to Ontario’s health care databases. Our objective was to more accurately determine the 10-year risk of major cardiovascular events after exposure to E. coli O157:H7.     

Being in the thick of things: context-dependent network centrality in a captive flock of American flamingos

We test the hypothesis that the relationship between networks resulting from unresolved agonistic interactions (URI) and social dominance was context-dependent in a captive group of American Flamingos (Phoenicopterus ruber ruber). URI formed networks that differed substantially from the dominance network and depended on the context in which the interactions occurred. Betweenness centrality in the URI network on the region (“the island”) where nesting took place was strongly correlated with dominance score. This correlation was particularly strong in the case of males, but, in both sexes, the dominant individual in a dyad was likely to have a higher betweenness centrality in the island URI. On the other hand, betweenness centrality in URI networks at the feeder did not show any relationship with dominance, but was associated with observed visits to the feeder. Thus, centrality in both the island URI network and the feeder URI network was associated with access to a resource over which individuals competed. Along with other results suggesting that non-dominance interactions may form social networks distinct from, but related to, dominance networks, our results support the hypothesis that relationships within animal social groups can be modeled as a series of distinct but inter-related networks.     

Identification of conditioned medium proteins from human cancer cells adapted to serum-free conditions

Recent studies have shown that human cancer cell lines can be adapted to grow in serum-free, unsupplemented RPMI-1640 (RO) medium. We have developed similar techniques to rapidly identify proteins of interest in serum-free conditioned medium (CM) of human lung cancer cell lines. Classic and variant small cell lung cancer (SCLC) lines were adapted to growth in RO medium. CM from each line was concentrated and fractionated on an anion-exchange column of a fast protein liquid chromatography system. Concentrates of each fraction were loaded onto lanes of minigels of an automated electrophoresis system. Analysis of the chromatograms reveals peaks seen only in CM of the classic SCLC lines. Electrophoretic analysis of the fractions containing these peaks reveal protein bands distinguishing between the subtypes of human SCLC. One protein was purified to homogeneity with subsequent reversed-phase chromatography and identified by protein microsequencing as histone H2B. These automated techniques have general use in the rapid identification of CM proteins associated with the differentiation or progression of the many types of neoplastic cells which can be adapted to growth in RO medium.     

Renin inhibitors for the treatment of hypertension: design and optimization of a novel series of spirocyclic piperidines

The discovery and SAR of a novel series of spirocyclic renin inhibitors are described herein. It was found that by restricting the northern aromatic plate to the bioactive conformation through spirocyclization, increase in renin potency and decrease in hERG affinity could both be realized. When early members of this series were found to be potent time-dependent CYP3A4 inhibitors, two distinct strategies to address this liability were explored and this effort culminated in the identification of compound 31 as an optimized renin inhibitor.     

The effect of structural complexity, prey density, and "predator-free space" on prey survivorship at created oyster reef mesocosms

Interactions between predators and their prey are influenced by the habitat they occupy. Using created oyster (Crassostrea virginica) reef mesocosms, we conducted a series of laboratory experiments that created structure and manipulated complexity as well as prey density and "predator-free space" to examine the relationship between structural complexity and prey survivorship. Specifically, volume and spatial arrangement of oysters as well as prey density were manipulated, and the survivorship of prey (grass shrimp, Palaemonetes pugio) in the presence of a predator (wild red drum, Sciaenops ocellatus) was quantified. We found that the presence of structure increased prey survivorship, and that increasing complexity of this structure further increased survivorship, but only to a point. This agrees with the theory that structural complexity may influence predator-prey dynamics, but that a threshold exists with diminishing returns. These results held true even when prey density was scaled to structural complexity, or the amount of "predator-free space" was manipulated within our created reef mesocosms. The presence of structure and its complexity (oyster shell volume) were more important in facilitating prey survivorship than perceived refugia or density-dependent prey effects. A more accurate indicator of refugia might require "predator-free space" measures that also account for the available area within the structure itself (i.e., volume) and not just on the surface of a structure. Creating experiments that better mimic natural conditions and test a wider range of "predator-free space" are suggested to better understand the role of structural complexity in oyster reefs and other complex habitats.     

Intermediate states of ribonuclease III in complex with double-stranded RNA

Bacterial ribonuclease III (RNase III) can affect RNA structure and gene expression in either of two ways: as a processing enzyme that cleaves double-stranded (ds) RNA, or as a binding protein that binds but does not cleave dsRNA. We previously proposed a model of the catalytic complex of RNase III with dsRNA based on three crystal structures, including the endonuclease domain of RNase III with and without bound metal ions and a dsRNA binding protein complexed with dsRNA. We also reported a noncatalytic assembly observed in the crystal structure of an RNase III mutant, which binds but does not cleave dsRNA, complexed with dsRNA. We hypothesize that the RNase III*dsRNA complex can exist in two functional forms, a catalytic complex and a noncatalytic assembly, and that in between the two forms there may be intermediate states. Here, we present four crystal structures of RNase III complexed with dsRNA, representing possible intermediates.     

Evolution of larval segment position across 12 Drosophila species*

Many developmental traits that are critical to the survival of the organism are also robust. These robust traits are resistant to phenotypic change in the face of variation. This presents a challenge to evolution. In this article, we asked whether and how a well-established robust trait, Drosophila segment patterning, changed over the evolutionary history of the genus. We compared segment position scaled to body length at the first-instar larval stage among 12 Drosophila species. We found that relative segment position has changed many times across the phylogeny. Changes were frequent, but primarily small in magnitude. Phylogenetic analysis demonstrated that rates of change in segment position are variable along the Drosophila phylogenetic tree, and that these changes can occur in short evolutionary timescales. Correlation between position shifts of segments decreased as the distance between two segments increased, suggesting local control of segment position. The posterior-most abdominal segment showed the highest magnitude of change on average, had the highest rate of evolution between species, and appeared to be evolving more independently as compared to the rest of the segments. This segment was exceptionally elongated in the cactophilic species in our dataset, raising questions as to whether this change may be adaptive.