Fitness of wAlbB Wolbachia Infection in Aedes aegypti: Parameter Estimates in an Outcrossed Background and Potential for Population Invasion

Wolbachia endosymbionts are potentially useful tools for suppressing disease transmission by Aedes aegypti mosquitoes because Wolbachia can interfere with the transmission of dengue and other viruses as well as causing deleterious effects on their mosquito hosts. Most recent research has focused on the wMel infection, but other infections also influence viral transmission and may spread in natural populations. Here, we focus on the wAlbB infection in an Australian outbred background and show that this infection has many features that facilitate its invasion into natural populations including strong cytoplasmic incompatibility, a lack of effect on larval development, an equivalent mating success to uninfected males and perfect maternal transmission fidelity. On the other hand, the infection has deleterious effects when eggs are held in a dried state, falling between wMel and the more virulent wMelPop Wolbachia strains. The impact of this infection on lifespan also appears to be intermediate, consistent with the observation that this infection has a titer in adults between wMel and wMelPop. Population cage experiments indicate that the wAlbB infection establishes in cages when introduced at a frequency of 22%, suggesting that this strain could be successfully introduced into populations and subsequently persist and spread.     

Comprehensive transposon mutant library of Pseudomonas aeruginosa

We have developed technologies for creating saturating libraries of sequence-defined transposon insertion mutants in which each strain is maintained. Phenotypic analysis of such libraries should provide a virtually complete identification of nonessential genes required for any process for which a suitable screen can be devised. The approach was applied to Pseudomonas aeruginosa, an opportunistic pathogen with a 6.3-Mbp genome. The library that was generated consists of 30,100 sequence-defined mutants, corresponding to an average of five insertions per gene. About 12% of the predicted genes of this organism lacked insertions; many of these genes are likely to be essential for growth on rich media. Based on statistical analyses and bioinformatic comparison to known essential genes in E. coli, we estimate that the actual number of essential genes is 300-400. Screening the collection for strains defective in two defined multigenic processes (twitching motility and prototrophic growth) identified mutants corresponding to nearly all genes expected from earlier studies. Thus, phenotypic analysis of the collection may produce essentially complete lists of genes required for diverse biological activities. The transposons used to generate the mutant collection have added features that should facilitate downstream studies of gene expression, protein localization, epistasis, and chromosome engineering.     

Screening for Candida auris in patients admitted to eight intensive care units in England, 2017 to 2018

Background Candida auris is an emerging multidrug-resistant fungal pathogen associated with bloodstream, wound and other infections, especially in critically ill patients. C. auris carriage is persistent and is difficult to eradicate from the hospital environment.AimWe aimed to pilot admission screening for C. auris in intensive care units (ICUs) in England to estimate prevalence in the ICU population and to inform public health guidance.MethodsBetween May 2017 and April 2018, we screened admissions to eight adult ICUs in hospitals with no previous cases of C. auris, in three major cities. Swabs were taken from the nose, throat, axilla, groin, perineum, rectum and catheter urine, then cultured and identified using matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF MS). Patient records were linked to routine ICU data to describe and compare the demographic and health indicators of the screened cohort with a national cohort of ICU patients admitted between 2016 and 2017.ResultsAll C. auris screens for 921 adults from 998 admissions were negative. The upper confidence limit of the pooled prevalence across all sites was 0.4%. Comparison of the screened cohort with the national cohort showed it was broadly similar to the national cohort with respect to demographics and co-morbidities.ConclusionThese findings imply that C. auris colonisation among patients admitted to ICUs in England is currently rare. We would not currently recommend widespread screening for C. auris in ICUs in England. Hospitals should continue to screen high-risk individuals based on local risk assessment.     

Endoscopic mucosal resection of 161 cases of large sessile or flat colorectal polyps

OBJECTIVE: Large sessile or flat colorectal polyps, which are traditionally treated surgically, may be amenable to endoscopic mucosal resection (EMR), often using a piecemeal method. Appropriate selection of lesions and a careful technique may enhance the efficacy of EMR for polyps >or=20 mm in diameter without compromising safety. The aim of this study was to identify the factors that may be predictive of the risk of polyp recurrence. MATERIAL AND METHODS: A retrospective analysis was conducted on the outcome of 161 polyps >or=20 mm in diameter, treated by piecemeal EMR at a single centre using the "lift and cut" technique. All records were reviewed for polyp size, site, morphology and histology. Polypectomy technique, patient follow-up, polyp recurrence and surgical interventions were also recorded. RESULTS: Over an 8-year period, 161 colonic polyps measuring >or=20 mm were removed by EMR. Follow-up data were available for 149 cases (93%) with a mean polyp diameter of 32.5 mm; the total success rate of endoscopic polyp removal was 95.4%. The number of cases requiring 1, 2, 3, 4 and 6 attempts at EMR was 89 (60%), 36 (24%), 14 (9%), 2 (1.3%) and 1 (0.7%), respectively. Recurrence was significantly related to polyp size (p<0.001). There was no statistically significant relationship between site and recurrence. Seven patients (4.6%) underwent surgical intervention after EMR because of failed clearance. There were no post-EMR perforations and significant bleeding was reported in only two patients (1.7%). CONCLUSIONS: With careful attention to technique, piecemeal EMR is a safe option for the resection of most sessile and flat colorectal polyps >or=20 mm in size. A stricter follow-up may be required for larger lesions because of a higher risk of recurrence.     

Reactions to a targeted intervention to increase fecal occult blood testing among average-risk adults waiting for screening colonoscopy

BACKGROUND:

Increasing demand combined with limited capacity has resulted in long wait times for average-risk adults referred for screening colonoscopy for colorectal cancer. Management of patients on these growing wait lists is an emerging clinical issue.

OBJECTIVE:

To inform the content and design of a mailed targeted invitation for patients to undergo annual fecal occult blood testing (FOBT) while awaiting colonoscopy.

METHODS:

Focus groups (FGs) with average-risk patients on a wait list for screening colonoscopy at a high-throughput academic outpatient colonoscopy facility were conducted. During each FG session, feedback regarding a range of materials under consideration for the planned intervention was elicited using a semistructured facilitator guide. The FG sessions were recorded and transcribed verbatim, and analyzed using the constant comparative method to identify key themes.

RESULTS:

Findings from the three FGs (n=28) suggested that average-risk patients on a wait list for screening colonoscopy would be receptive to a targeted intervention recommending they undergo FOBT while waiting. Participants indicated that the invitation to undergo FOBT was an important acknowledgement that they were on an actively managed list, and that a mechanism to ensure that they were correctly triaged while waiting was in place. Several specific suggestions to improve the design of the targeted intervention were obtained.

CONCLUSIONS:

Results of the present study provide useful information for developing effective strategies to manage average-risk individuals facing long wait times for screening colonoscopy.     

Sustained melatonin treatment blocks body mass, pelage, reproductive, and fever responses to short day lengths in female Siberian hamsters

Winter imposes physiological challenges on individuals including increased thermoregulatory demands, risk of infection, and decreased food availability. To survive these challenges, animals living outside the tropics must appropriately distribute their energetic costs across the year, including reproduction and immune function. Individuals of many species use the annual cycle of changing day lengths (photoperiod), which is encoded by the nightly duration of melatonin secretion, to adjust physiology. Siberian hamsters exposed to short days (SD) (long nights/prolonged endogenous melatonin secretion) enhance some aspects of immune function, but curtail other energetically expensive immune functions including the febrile response. The purpose of this study was twofold. First, we determined whether sustained melatonin treatment would inhibit the development of the SD phenotype in female hamsters as it does in males. Second, we examined whether the SD attenuation of fever would be blocked by continuous exposure to exogenous melatonin. Hamsters were implanted with melatonin or empty capsules, housed in either long days (LD) or SD for 8-9 weeks, and then challenged with lipopolysaccharide; body temperature and locomotor activity were recorded. Unlike hamsters with empty capsules, hamsters with melatonin implants did not respond to SD and maintained a LD phenotype including summer-like spleen, uterine and body masses, and pelage characteristics. Further, sustained melatonin treatment blocked the SD attenuation of febrile responses and prolonged the behavioral components of the sickness response. These results suggest that the daily fluctuations in endogenous melatonin may be masked by continuous exposure to exogenous melatonin, thus inhibiting functional photoperiodic responses to SD.     

Developmental synaptic regulator,TWEAK/Fn14 signaling,is a determinant of synaptic function in models of stroke and neurodegeneration

Identifying molecular mediators of neural circuit development and/or function that contribute to circuit dysfunction when aberrantly reengaged in neurological disorders is of high importance. The role of the TWEAK/Fn14 pathway, which was recently reported to be a microglial/neuronal axis mediating synaptic refinement in experience-dependent visual development, has not been explored in synaptic function within the mature central nervous system. By combining electrophysiological and phosphoproteomic approaches, we show that TWEAK acutely dampens basal synaptic transmission and plasticity through neuronal Fn14 and impacts the phosphorylation state of pre- and postsynaptic proteins in adult mouse hippocampal slices. Importantly, this is relevant in two models featuring synaptic deficits. Blocking TWEAK/Fn14 signaling augments synaptic function in hippocampal slices from amyloid-beta–overexpressing mice. After stroke, genetic or pharmacological inhibition of TWEAK/Fn14 signaling augments basal synaptic transmission and normalizes plasticity. Our data support a glial/neuronal axis that critically modifies synaptic physiology and pathophysiology in different contexts in the mature brain and may be a therapeutic target for improving neurophysiological outcomes.

Neural circuit patterning, refinement, and plasticity are enabled by the dynamic strengthening, weakening, and pruning of chemical synapses in response to circuit activity. However, synapse loss and reduced plasticity are early hallmarks of chronic neurological disorders such as autism, schizophrenia and Alzheimer’s disease (AD) (1–3). It is therefore hypothesized that the underlying molecular mechanisms of pruning, although normally balanced in health, are dysregulated in disease. Particularly interesting is the notion that the mechanisms responsible for the reduction in functional synapses in disease reflect the aberrant reactivation of pathways important for synapse elimination in development. For example, in an AD model, synapse elimination was shown to be mediated by the complement pathway in the hippocampus (HC), reflecting aberrant reactivation of complement-dependent synapse elimination that occurs in the dorsal lateral geniculate nucleus (dLGN) of the thalamus during visual development (4). In such a paradigm, the reactivation of developmental mechanisms enables pathways that can act universally across different ages, circuits, and brain regions. Thus, the mechanisms underlying normal circuit development and their potential reactivation as key contributors to neurological diseases are areas of deep interest.In addition to chronic neurological disorders, circuitry changes also occur in acute ischemic stroke, the second leading cause of death worldwide and a cause of debilitating long-term disability. Interruptions in blood flow that deprive neurons of oxygen and nutrients result in significant cell death, followed by deficits in neurophysiological activity that are associated with poor motor recovery (5). Remarkably, the adult brain can undergo some degree of spontaneous poststroke recovery, apparently by engaging neuroplasticity mechanisms including remapping, synaptogenesis, and synaptic strengthening (5, 6). Despite these adaptations, over half of ischemic stroke patients fail to recover completely and continue to experience persistent long-term disability (7). The underlying signaling pathways that regulate synaptic physiology after stroke are an active topic of investigation.TNF-like weak inducer of apoptosis (TWEAK) protein, originally discovered as a cytokine produced by macrophages (8), signals through its injury-inducible transmembrane receptor, FGF-inducible molecule-14 (Fn14) (9). Consequently, the function of TWEAK/Fn14 signaling was elucidated as a driver of tissue remodeling in contexts of injury and disease in a variety of organ systems (10). Recently, findings have suggested a role for the TWEAK/Fn14 pathway in the central nervous system (CNS). Namely, several compelling observations indicate that TWEAK signaling through Fn14 might be a key molecular modulator of synaptic function in contexts of neurological challenge. TWEAK and Fn14 are up-regulated in the CNS in AD (11, 12, 13 and SI Appendix, Fig. S6A) and after ischemic stroke in humans and mice (14–16). Importantly, TWEAK/Fn14 signaling was also recently shown to be a pathway necessary for synapse maturation during experience-dependent visual development. Light-induced up-regulation of Fn14 in thalamocortical excitatory neurons and corresponding up-regulation of TWEAK in microglia mediate the elimination of weak synapses and strengthening of remaining synapses in the dLGN (17, 18). Indeed, the communication between neurons and supporting microglia has emerged as a key mechanism regulating neuronal circuitry, with microglia deploying their ramified processes to continuously survey and refine synapses in response to neural activity. Interestingly, TWEAK expression has also been shown to be microglia-enriched in the mouse cortex (19), suggesting that it may play a role in multiple brain regions. Thus, like the complement pathway, the TWEAK/Fn14 pathway could be an important regulator of synapse biology in visual development which is re-engaged and acts generally in different ages and brain regions to contribute to pathology.The involvement of TWEAK/Fn14 signaling in synapse physiology or pathophysiology outside of the developing visual system is unknown. We considered it to be a strong candidate modifier of synaptic function in adults given that Fn14 is up-regulated and required for synaptic refinement in experience-dependent visual development, and TWEAK and Fn14 are up-regulated in contexts of neurological injury/disease, suggesting that the TWEAK/Fn14 system is tuned to periods of substantial change in neuronal activity levels or environment (e.g., eye opening, ischemic stroke). We employed HC slices to test the hypothesis that the TWEAK/Fn14 pathway regulates synaptic function in adult mice and in different disease contexts and delineate its mechanism of action. Herein, we reveal that TWEAK, through neuronal Fn14, mediates acute dampening of basal synaptic transmission and synaptic plasticity in hippocampal slices from mature mice. Furthermore, we demonstrate that TWEAK/Fn14 signaling broadly impacts the phosphorylation state of critical synaptic proteins, suggesting a general role in synapse modulation. Finally, we show that pathway deficiency or pharmacological inhibition of TWEAK/Fn14 signaling augments synaptic transmission and plasticity in amyloid-beta (Aβ)–overexpressing mice and post ischemic stroke animals, two model systems featuring synaptic functional deficits. Thus, our results support that TWEAK/Fn14 constitutes a synaptic regulatory pathway with therapeutic potential for CNS disorders in the adult brain.