Colonisation and persistence of Escherichia coli 0157:H7 in the bovine gastro-intestinal tract

. coli 0157:H7 is a cause of infectious intestinal disease in humans, primarily in developed countries. Although not as prevalent as certain other bacterial enteropathogens, it is of particular concern due to the effect of a secreted virulence factor, shiga toxin (Stx), which causes potentially fatal systemic sequelae. Domestic ruminants, most frequently cattle, are consistently identified as the source of infection and transmission may occur through a variety of routes. The bacterium asymptomatically colonises the gastro- intestinal tracts (GIT) of its ruminant hosts. Adaptation to this niche is responsible for the presence of the organism within the environment. The principal aim during this study was to develop appropriate in vitro and in vivo systems to examine colonisation mechanisms of E. coli 0157:H7 in the bovine GIT. An adherence assay on cultured tissue explants was developed to compare different factors involved in E. coli 0157:H7 adherence. In two separate experiments the contribution of factors involved in intimate attachment, thought to be essential for virulence in humans, was assessed. The ability to intimately attach did not affect the level of E. coli 0157:H7 adherence to bovine intestinal epithelium in vitro. A strain lacking the genes required for intimate attachment however exhibited enhanced adherence to bovine Peyer's patch. The other strains did not exhibit a tropism for any of the tissue types examined.The most relevant system to assess the behaviour of E. coli 0157:H7 is within its natural host. Persistent colonisation of weaned calves was achieved for a number of isolates marked by nalidixic acid resistance, including a Stx negative strain that colonised at a similar level and duration to the Stx positive co- strain. At the conclusion of each calf colonisation experiment, those individuals still shedding the organism were examined under necropsy to determine its distribution. The first attempts failed to recover the organism in significant numbers at any site examined despite it being present in ante -mortem faeces. One explanation was that the organism was multiplying primarily in the distal rectum. Further necropsies revealed that the organism was colonising the mucosal surface of the distal 3 cm of the rectum via intimate attachment and confirmed that this phenomenon was indeed typical of persistently colonised calves. This small region contained a high density of lymphoid tissue. Other bacteria are known to have a tropism for follicle- associated iv epithelium and it is proposed that E. coli 0157:H7 possesses an FAE specific factor that mediates its unique distribution within the bovine GIT and is responsible for many aspects of its biology resulting in its importance as a human pathoge

Development and evaluation of a novel protective device for upper gastrointestinal endoscopy in the COVID-19 pandemic: the EBOX

Background During the COVID-19 pandemic, aerosol-generating procedures such as upper gastrointestinal endoscopy (UGIE) have been considered high risk. We designed a novel acrylic box (endoscopy box (EBOX)) with the intention of limiting aerosol and droplet spread during such procedures. We evaluated clinical utility, impact on the endoscopy team and also assessed the impact of the EBOX on macroscopic droplet spread from a simulated cough during UGIE. Methods Clinical utility was evaluated prospectively via EBOX use on 15 patients undergoing endoscopic retrograde cholangiopancreatography (13) or endoscopic ultrasound (2). Feedback was recorded from the endoscopy team regarding ease of positioning, impact of the EBOX on procedural performance and cleaning. A cough was simulated via explosion of a hyperinflated balloon containing 0.75 mL of ultraviolet disclosing lotion within the oral cavity of a mannequin, with and without the EBOX. Macroscopic spread was then evaluated with a ultraviolet torch. Results Three endoscopists and the team members found that the EBOX did not hamper the procedure and felt it was a useful adjunct to full personal protective equipment (PPE). Simulated cough without the EBOX identified macroscopic spread up to 2.3 m away from the patient’s mouth as well as onto key areas such as the exposed neck of the endoscopist, which is not considered in current PPE guidance. Simulated cough using the EBOX significantly reduced macroscopic spread onto key areas of the healthcare workers. Conclusions The EBOX is a valuable adjunct to recommended PPE for UGIE, but still allows these procedures to be performed in the standard manner

Stiff oscillatory systems, delta jumps and white noise

Two model problems for stiff oscillatory systems are introduced. Both comprise a linear superposition of N >> 1 harmonic oscillators used as a forcing term for a scalar ODE. In the first case the initial conditions are chosen so that the forcing term approximates a delta function as N tends to infinity, and in the second case so that it approximates white noise. In both cases the fastest natural frequency of the oscillators is O(N). The model problems are integrated numerically in the stiff regime where the time step is of size O(1/N). The convergence of the algorithms is studied in this case in the limit of N tending to infinity and the time step tending to zero. For the white noise problem both strong and weak convergence are considered

The Discovery of XY Sex Chromosomes in a \u3cem\u3eBoa\u3c/em\u3e and \u3cem\u3ePython\u3c/em\u3e

For over 50 years, biologists have accepted that all extant snakes share the same ZW sex chromosomes derived from a common ancestor [1, 2, 3], with different species exhibiting sex chromosomes at varying stages of differentiation. Accordingly, snakes have been a well-studied model for sex chromosome evolution in animals [1, 4]. A review of the literature, however, reveals no compelling support that boas and pythons possess ZW sex chromosomes [2, 5]. Furthermore, phylogenetic patterns of facultative parthenogenesis in snakes and a sex-linked color mutation in the ball python (Python regius) are best explained by boas and pythons possessing an XY sex chromosome system [6, 7]. Here we demonstrate that a boa (Boa imperator) and python (Python bivittatus) indeed possess XY sex chromosomes, based on the discovery of male-specific genetic markers in both species. We use these markers, along with transcriptomic and genomic data, to identify distinct sex chromosomes in boas and pythons, demonstrating that XY systems evolved independently in each lineage. This discovery highlights the dynamic evolution of vertebrate sex chromosomes and further enhances the value of snakes as a model for studying sex chromosome evolution

Correlates of criminal victimisation among police cell detainees in Victoria, Australia

People with mental illness are more likely to be crime victims than others; however, little is known about the relationship between offending and victimisation among mentally ill offenders. This study investigated the rates and types of victimisation among people detained in police cells (N = 764), with and without histories of mental illness. Those with mental disorders were 1.56 times (95% CI = 1.11–2.17) more likely to be victims of violent crimes than other detainees. Some subgroups of people with mental disorders were not over-represented as victims, raising the possibility that they were less inclined to report certain types of crimes. Implications are discussed with reference to police practice