D-Serine reduces the expression of the cytopathic genotoxin colibactin.

Some Escherichia coli strains harbour the pks island, a 54 kb genomic island encoding the biosynthesis genes for a genotoxic compound named colibactin. In eukaryotic cells, colibactin can induce DNA damage, cell cycle arrest and chromosomal instability. Production of colibactin has been implicated in the development of colorectal cancer (CRC). In this study, we demonstrate the inhibitory effect of D-Serine on the expression of the pks island in both prototypic and clinically-associated colibactin-producing strains and determine the implications for cytopathic effects on host cells. We also tested a comprehensive panel of proteinogenic L-amino acids and corresponding D-enantiomers for their ability to modulate clbB transcription. Whilst several D-amino acids exhibited the ability to inhibit expression of clbB, D-Serine exerted the strongest repressing activity (>3.8-fold) and thus, we focussed additional experiments on D-Serine. To investigate the cellular effect, we investigated if repression of colibactin by D-Serine could reduce the cytopathic responses normally observed during infection of HeLa cells with pks + strains. Levels of γ-H2AX (a marker of DNA double strand breaks) were reduced 2.75-fold in cells infected with D-Serine treatment. Moreover, exposure of pks + E. coli to D-Serine during infection caused a reduction in cellular senescence that was observable at 72 h post infection. The recent finding of an association between pks-carrying commensal E. coli and CRC, highlights the necessity for the development of colibactin targeting therapeutics. Here we show that D-Serine can reduce expression of colibactin, and inhibit downstream cellular cytopathy, illuminating its potential to prevent colibactin-associated disease.

Cerebrospinal fluid and plasma ascorbate concentrations following subarachnoid haemorrhage.

Background: Ascorbate, the biologically active form of vitamin C, is the primary neural anti-oxidant. Ascorbate concentrations have never been quantified following aneurysmal subarachnoid haemorrhage (aSAH). Objective: To quantify plasma and cerebrospinal fluid (CSF) ascorbate concentrations in patients following SAH. Design Setting Participants Main Outcome Measures: Cohort study in which plasma and CSF ascorbate concentrations were measured longitudinally in 12 aSAH patients admitted to a quaternary referral intensive care unit and compared to one-off samples obtained from 20 pregnant women prior to delivery in a co-located obstetric hospital. Data are median [interquartile range] or median (95 % confidence intervals). Results: Forty-eight plasma samples were obtained from the 12 aSAH patients (eight females, age 62 [53-68] years). Eight participants with extra-ventricular drains provided 31 paired CSF-plasma samples. Single plasma and CSF samples were obtained from 20 pregnant women (age 35 [31-37] years). Initial plasma and CSF ascorbate concentrations post aSAH were less than half those in pregnant controls (plasma: aSAH: 31 [25-39] µmol/L vs. comparator: 64 [59-77] µmol/L; P < 0.001 and CSF: 116 [80-142] µmol/L vs. 252 [240-288] µmol/L; P < 0.001). Post aSAH there was a gradual reduction in the CSF:plasma ascorbate ratio from ∼4:1 to ∼1:1. Six (50 %) patients developed vasospasm and CSF ascorbate concentrations were lower in these patients (vasospasm: 61 (25, 97) vs. no vasospasm: 110 (96, 125) µmol/L; P = 0.01). Conclusion: Post aSAH there is a marked reduction in CSF ascorbate concentration that is most prominent in those who develop vasospasm.

Control of resistance against bacteriophage killing by a metabolic regulator in meningitis-associated Escherichia coli.

Ecologically beneficial traits in bacteria are encoded by intrinsic and horizontally acquired genes. However, such traits are not universal, and the highly mosaic nature of bacterial genomes requires control at the transcriptional level to drive these processes. It has emerged that regulatory flexibility is widespread in the Escherichia coli species, whereby preexisting transcription factors can acquire new and unrelated roles in regulating beneficial traits. DsdC is the regulator of D-serine tolerance in E. coli, is essential for D-serine catabolism, and is often encoded by two copies in neonatal meningitis-associated E. coli (NMEC). Here, we reveal that DsdC is a global regulator of transcription in NMEC and does not require D-serine for the control of novel beneficial traits. We show that DsdC binds the chromosome in an unusual manner, with many binding sites arranged in clusters spanning entire operons and within gene coding sequences, such as neuO. Importantly, we identify neuO as the most significantly down-regulated gene in a strain deleted for both dsdC copies, in both the presence and absence of D-serine. NeuO is prophage encoded in several NMEC K1 isolates and mediates capsule O-acetylation but has no effect on attachment to or invasion of human brain endothelial cells. Instead, we demonstrate that NeuO provides resistance against K1 bacteriophage attack and that this critical function is regulated by DsdC. This work highlights how a horizontally acquired enzyme that functions in cell-surface modulation can be controlled by an intrinsic regulator to provide a key ecological benefit to an E. coli pathotype.

Evaluation of a Structured Nutrition Competence Program for Dietitian Assistants.

OBJECTIVE: To explore the perspectives of dietitian assistants in a tertiary teaching hospital in Sydney, Australia, following the implementation of a formal competence and professional development program. METHODS: All currently employed dietitian assistants at a tertiary teaching hospital in Sydney were eligible to participate. Semi-structured interviews were undertaken by two student dietitians. Transcripts were returned to participants for interviewee transcript review and further clarification of information. Transcripts were qualitatively described. RESULTS: A total of 9 dietitian assistants participated in interviews in October 2019. The average age of participants was 45.11 yrs (range 29-59) and 90% were female (n=8). The average length of employment was 197 months (range 3-516). Three themes emerged including: (a) new job satisfaction, (b) positive influence of the dietitian assistant educator, and (c) challenges of new processes and responsibilities. CONCLUSION: A supported structured competence and professional development program has provided dietitian assistants with new skills and renewed job satisfaction. Further research should consider the impact of the newly developed skills of dietitian assistants on patient care and outcome measures.

d-Serine induces distinct transcriptomes in diverse Escherichia coli pathotypes.

Appropriate interpretation of environmental signals facilitates niche specificity in pathogenic bacteria. However, the responses of niche-specific pathogens to common host signals are poorly understood. d-Serine (d-ser) is a toxic metabolite present in highly variable concentrations at different colonization sites within the human host that we previously found is capable of inducing changes in gene expression. In this study, we made the striking observation that the global transcriptional response of three Escherichia coli pathotypes - enterohaemorrhagic E. coli (EHEC), uropathogenic E. coli (UPEC) and neonatal meningitis-associated E. coli (NMEC) - to d-ser was highly distinct. In fact, we identified no single differentially expressed gene common to all three strains. We observed the induction of ribosome-associated genes in extraintestinal pathogens UPEC and NMEC only, and the induction of purine metabolism genes in gut-restricted EHEC, and UPEC indicating distinct transcriptional responses to a common signal. UPEC and NMEC encode dsdCXA - a genetic locus required for detoxification and hence normal growth in the presence of d-ser. Specific transcriptional responses were induced in strains accumulating d-ser (WT EHEC and UPEC/NMEC mutants lacking the d-ser-responsive transcriptional activator DsdC), corroborating the notion that d-ser is an unfavourable metabolite if not metabolized. Importantly, many of the UPEC-associated transcriptome alterations correlate with published data on the urinary transcriptome, supporting the hypothesis that d-ser sensing forms a key part of urinary niche adaptation in this pathotype. Collectively, our results demonstrate distinct pleiotropic responses to a common metabolite in diverse E. coli pathotypes, with important implications for niche selectivity.

Penetrating gluteal injuries in North West London: a retrospective cohort study and initial management guideline.

BACKGROUND: Penetrating gluteal injuries (PGIs) are an increasingly common presentation to major trauma centers (MTCs) in the UK and especially in London. PGIs can be associated with mortality and significant morbidity. There is a paucity of consistent guidance on how best to investigate and manage these patients. METHODS: A retrospective cohort study was performed by interrogating prospectively collected patient records for PGI presenting to a level 1 MTC in London between 2017 and 2019. RESULTS: There were 125 presentations with PGI, accounting for 6.86% of all penetrating injuries. Of these, 95.2% (119) were male, with a median age of 21 (IQR 18-29), and 20.80% (26) were under 18. Compared with the 3 years prior to this study, the number of PGI increased by 87%. The absolute risk (AR) of injury to a significant structure was 27.20%; the most frequently injured structure was a blood vessel (17.60%), followed by the rectum (4.80%) and the urethra (1.60%). The AR by anatomic quadrant of injury was highest in the lower inner quadrant (56%) and lowest in the upper outer quadrant (14%). CT scanning had an overall sensitivity of 50% and specificity of 92.38% in identifying rectal injury. DISCUSSION: The anatomic quadrant of injury can be helpful in stratifying risk of rectal and urethral injuries when assessing a patient in the emergency department. Given the low sensitivity in identifying rectal injury on initial CT, this data supports assesing any patients considered at high risk of rectal injury with an examination under general anesthetic with or without rigid sigmoidoscopy. The pathway has created a clear tool that optimizes investigation and treatment, minimizing the likelihood of missed injury or unnecessary use of resources. It therefore represents a potential pathway other centers receiving a similar trauma burden could consider adopting. LEVEL OF EVIDENCE: 2b.

Plastic Circuits: Regulatory Flexibility in Fine Tuning Pathogen Success.

Bacterial pathogens employ diverse fitness and virulence mechanisms to gain an advantage in competitive niches. These lifestyle-specific traits require integration into the regulatory network of the cell and are often controlled by pre-existing transcription factors. In this review, we highlight recent advances that have been made in characterizing this regulatory flexibility in prominent members of the Enterobacteriaceae. We focus on the direct global interactions between transcription factors and their target genes in pathogenic Escherichia coli and Salmonella revealed using chromatin immunoprecipitation coupled with next-generation sequencing. Furthermore, the implications and advantages of such regulatory adaptations in benefiting distinct pathogenic lifestyles are discussed.

Distinct intraspecies virulence mechanisms regulated by a conserved transcription factor.

Tailoring transcriptional regulation to coordinate the expression of virulence factors in tandem with the core genome is a hallmark of bacterial pathogen evolution. Bacteria encode hundreds of transcription factors forming the base-level control of gene regulation. Moreover, highly homologous regulators are assumed to control conserved genes between members within a species that harbor the same genetic targets. We have explored this concept in 2 Escherichia coli pathotypes that employ distinct virulence mechanisms that facilitate specification of a different niche within the host. Strikingly, we found that the transcription factor YhaJ actively regulated unique gene sets between intestinal enterohemorrhagic E. coli (EHEC) and extraintestinal uropathogenic E. coli (UPEC), despite being very highly conserved. In EHEC, YhaJ directly activates expression of type 3 secretion system components and effectors. Alternatively, YhaJ enhances UPEC virulence regulation by binding directly to the phase-variable type 1 fimbria promoter, driving its expression. Additionally, YhaJ was found to override the universal GAD acid tolerance system but exclusively in EHEC, thereby indirectly enhancing type 3 secretion pleiotropically. These results have revealed that within a species, conserved regulators are actively repurposed in a "personalized" manner to benefit particular lifestyles and drive virulence via multiple distinct mechanisms.

Control freaks-signals and cues governing the regulation of virulence in attaching and effacing pathogens.

Enterohaemorrhagic Escherichia coli (EHEC) mediates disease using a type 3 secretion system (T3SS), which is encoded on the locus of enterocyte effacement (LEE) and is tightly controlled by master regulators. This system is further modulated by a number of signals that help to fine-tune virulence, including metabolic, environmental and chemical signals. Since the LEE and its master regulator, Ler, were established, there have been numerous scientific advancements in understanding the regulation and expression of virulence factors in EHEC. This review will discuss the recent advancements in this field since our previous review, with a focus on the transcriptional regulation of the LEE.

Persistent mTORC1 signaling in cell senescence results from defects in amino acid and growth factor sensing.

Mammalian target of rapamycin complex 1 (mTORC1) and cell senescence are intimately linked to each other and to organismal aging. Inhibition of mTORC1 is the best-known intervention to extend lifespan, and recent evidence suggests that clearance of senescent cells can also improve health and lifespan. Enhanced mTORC1 activity drives characteristic phenotypes of senescence, although the underlying mechanisms responsible for increased activity are not well understood. We have identified that in human fibroblasts rendered senescent by stress, replicative exhaustion, or oncogene activation, mTORC1 is constitutively active and resistant to serum and amino acid starvation. This is driven in part by depolarization of senescent cell plasma membrane, which leads to primary cilia defects and a resultant failure to inhibit growth factor signaling. Further, increased autophagy and high levels of intracellular amino acids may act to support mTORC1 activity in starvation conditions. Interventions to correct these phenotypes restore sensitivity to the mTORC1 signaling pathway and cause death, indicating that persistent signaling supports senescent cell survival.

Building blocks to adopting a pay-for-performance model.

Pay for performance (P4P) is a payment approach used in healthcare that is based on clinical information-driven reform. The fundamental concept of this method is to tie payment to how well providers comply to practice standards. This article will analyze those concepts including the essential building blocks, models, and selected programs of P4Ps, as well as information technology's impact on P4Ps. The nurse manager and nurse executive need to be familiar with this method to participate in the evaluation and implementation of such plans.

Oxygen saturation levels in the first 30 minutes of life.

PURPOSE: To report a serendipitous finding from a larger investigation describing physiologic variability of healthy and sick pre- and full-term neonates transitioning to extrauterine life in whom the oxygen arterial saturations rose to 90% very quickly. SUBJECTS: Thirty-four healthy pre- and full-term neonates and 40 sick pre- and full-term neonates. DESIGN: Descriptive, comparative. METHODS: Within the first 15-30 seconds of life, a pulse oximeter probe was placed on the dorsum of the neonate's foot. The signal was uploaded from the Hewlett Packard Viridia cardiopulmonary/oxygen saturation monitor to a data acquisition module at the bedside. Healthcare personnel performed their routine caregiving procedures for the neonate beginning transition to extrauterine life. They were at liberty to administer oxygen when they felt it was clinically necessary. MAIN OUTCOME MEASURES: Oxygen saturation as measured by pulse oximetry. PRINCIPAL RESULTS: Oxygen saturation values reached higher levels much faster for all groups of neonates than what has been previously reported in the literature. CONCLUSIONS: In light of recent controversies regarding oxygen therapy, the practice of randomly administering oxygen to healthy infants at time of delivery should be examined.