Expression of RcrB confers resistance to hypochlorous acid in uropathogenic Escherichia coli.

To eradicate bacterial pathogens, neutrophils are recruited to the sites of infection, where they engulf and kill microbes through the production of reactive oxygen and chlorine species (ROS/RCS). The most prominent RCS is the antimicrobial oxidant hypochlorous acid (HOCl), which rapidly reacts with various amino acid side chains, including those containing sulfur and primary/tertiary amines, causing significant macromolecular damage. Pathogens like uropathogenic Escherichia coli (UPEC), the primary causative agent of urinary tract infections, have developed sophisticated defense systems to protect themselves from HOCl. We recently identified the RcrR regulon as a novel HOCl defense strategy in UPEC. Expression of the rcrARB operon is controlled by the HOCl-sensing transcriptional repressor RcrR, which is oxidatively inactivated by HOCl resulting in the expression of its target genes, including rcrB. The rcrB gene encodes a hypothetical membrane protein, deletion of which substantially increases UPEC's susceptibility to HOCl. However, the mechanism behind protection by RcrB is unclear. In this study, we investigated whether (i) its mode of action requires additional help, (ii) rcrARB expression is induced by physiologically relevant oxidants other than HOCl, and (iii) expression of this defense system is limited to specific media and/or cultivation conditions. We provide evidence that RcrB expression is sufficient to protect E. coli from HOCl. Furthermore, RcrB expression is induced by and protects from several RCS but not from ROS. RcrB plays a protective role for RCS-stressed planktonic cells under various growth and cultivation conditions but appears to be irrelevant for UPEC's biofilm formation. IMPORTANCE Bacterial infections pose an increasing threat to human health, exacerbating the demand for alternative treatments. Uropathogenic Escherichia coli (UPEC), the most common etiological agent of urinary tract infections (UTIs), are confronted by neutrophilic attacks in the bladder, and must therefore be equipped with powerful defense systems to fend off the toxic effects of reactive chlorine species. How UPEC deal with the negative consequences of the oxidative burst in the neutrophil phagosome remains unclear. Our study sheds light on the requirements for the expression and protective effects of RcrB, which we recently identified as UPEC's most potent defense system toward hypochlorous acid (HOCl) stress and phagocytosis. Thus, this novel HOCl stress defense system could potentially serve as an attractive drug target to increase the body's own capacity to fight UTIs.

Expression of RcrB confers resistance to hypochlorous acid in uropathogenic Escherichia coli.

To eradicate bacterial pathogens, neutrophils are recruited to the sites of infection, where they engulf and kill microbes through the production of reactive oxygen and chlorine species (ROS/RCS). The most prominent RCS is antimicrobial oxidant hypochlorous acid (HOCl), which rapidly reacts with various amino acids side chains, including those containing sulfur and primary/tertiary amines, causing significant macromolecular damage. Pathogens like uropathogenic Escherichia coli (UPEC), the primary causative agent of urinary tract infections (UTIs), have developed sophisticated defense systems to protect themselves from HOCl. We recently identified the RcrR regulon as a novel HOCl defense strategy in UPEC. The regulon is controlled by the HOCl-sensing transcriptional repressor RcrR, which is oxidatively inactivated by HOCl resulting in the expression of its target genes, including rcrB . rcrB encodes the putative membrane protein RcrB, deletion of which substantially increases UPEC's susceptibility to HOCl. However, many questions regarding RcrB's role remain open including whether (i) the protein's mode of action requires additional help, (ii) rcrARB expression is induced by physiologically relevant oxidants other than HOCl, and (iii) expression of this defense system is limited to specific media and/or cultivation conditions. Here, we provide evidence that RcrB expression is sufficient to E. coli 's protection from HOCl and induced by and protects from several RCS but not from ROS. RcrB plays a protective role for RCS-stressed planktonic cells under various growth and cultivation conditions but appears to be irrelevant for UPEC's biofilm formation. IMPORTANCE: Bacterial infections pose an increasing threat to human health exacerbating the demand for alternative treatment options. UPEC, the most common etiological agent of urinary tract infections (UTIs), are confronted by neutrophilic attacks in the bladder, and must therefore be well equipped with powerful defense systems to fend off the toxic effects of RCS. How UPEC deal with the negative consequences of the oxidative burst in the neutrophil phagosome remains unclear. Our study sheds light on the requirements for the expression and protective effects of RcrB, which we recently identified as UPEC's most potent defense system towards HOCl-stress and phagocytosis. Thus, this novel HOCl-stress defense system could potentially serve as an attractive drug target to increase the body's own capacity to fight UTIs.

Epidemiology and complications of anaesthesia in the French centres that participated to NECTARINE: A secondary analysis.

INTRODUCTION: Neonatal and infant anaesthesia are associated with a high risk of perioperative complications. The aim of the current study was to describe those risks in France using the French data from the NECTARINE study. MATERIAL AND METHODS: Data from the French centres that participated to the NECTARINE study were analysed. The primary goal of the study was the description of patients' characteristics, procedures and perioperative management and their comparison with the results of the European NECTARINE study. Secondary outcomes were the description of major perioperative complications and death. RESULTS: Overall, 926 procedures collected in 15 centres (all teaching hospitals) were analysed. Comparison between the French and European NECTARINE cohorts found few differences related to patients' characteristics and procedures. The rate of interventions for critical events (respiratory, haemodynamic, and metabolic) was similar between the two cohorts. Near-infrared spectroscopy monitoring was used in 12% of procedures. Nearly none of the thresholds for these interventions met the published standards. By day 30, complications (respiratory, haemodynamic, metabolic, renal, and liver failure) and death were observed in 14.4% [95% CI 11.6-16.4]% and 1.8% [95% CI 1.1-2.9] of cases, respectively. DISCUSSION: Although the health status of the patients in the French cohort was less severe, procedures, management and postoperative complications and mortality rates were similar to the European cohort. However, thresholds for interventions were often inadequate in both cohorts. Efforts should be undertaken to improve the knowledge and use of new monitoring devices in this population.

Perineural dexamethasone attenuates liposomal bupivacaine-induced delayed neural inflammation in mice in vivo.

BACKGROUND: Liposomal bupivacaine (Exparel®) is a sustained-release formulation of bupivacaine for use in surgical infiltration anaesthesia. We analysed the histological nerve toxicity and clinical effectiveness of perineural Exparel® alone or with added dexamethasone in a mouse model. METHODS: We assigned 98 mice receiving a perineural sciatic nerve injection into seven groups: sham (n=14, perineural saline), B (n=14, perineural bupivacaine), BDIP (n=14, perineural bupivacaine + intraperitoneal dexamethasone), BDPN (n=14, perineural bupivacaine + perineural dexamethasone), E (n=14, perineural Exparel®), EDIP (n=14, perineural Exparel® + intraperitoneal dexamethasone), and EDPN (n=14, perineural Exparel® + perineural dexamethasone). The duration of thermoalgesic and motor block was evaluated in 49 mice (seven mice randomly selected by group) every 30 min until recovery. Mice were killed for sciatic nerve histological assessment at 14 or 28 days. RESULTS: The median duration of motor block was 90, 120, 120, 120, 180, and 180 min and the duration of thermoalgesic block was 240, 300, 360, 360, 360, and 420 min for groups B, BDIP, BDPN, E, EDIP, and EDPN, respectively. The B group mice showed mild neural inflammation at 14 days and the E group mice showed mild neural inflammation at 28 days. Addition (intraperitoneal or perineural) of dexamethasone reduced neural inflammation induced by bupivacaine, whereas only perineural dexamethasone reduced neural inflammation induced by Exparel®. CONCLUSIONS: Perineural or systemic dexamethasone had a protective effect against the neural inflammation induced by bupivacaine, and perineural dexamethasone attenuated delayed inflammation induced by perineural Exparel®.

A New Step Toward Evidence of In Vivo Perineural Dexamethasone Safety: An Animal Study.

BACKGROUND AND OBJECTIVES: The aim of this study was to analyze histological nerve toxicity of perineural dexamethasone administration in combination with ropivacaine on mice. Efficacy of perineural dexamethasone in combination with regional anesthesia is clearly demonstrated. However, the safety of this procedure is still a matter of debate. METHODS: A sciatic nerve block was performed on 90 mice. Five groups, each containing 18 mice assigned randomly, were used in these experiments: the sham group (isotonic saline solution), R group (perineural ropivacaine), D group (perineural dexamethasone), RDPN group (perineural ropivacaine and perineural dexamethasone), and the RDS group (perineural ropivacaine and systemic dexamethasone). Sensory and motor blocks were evaluated every 30 minutes for 14 hours. Fourteen and 28 days after this procedure, 9 mice in each group were killed for sciatic nerve histological assessment. RESULTS: No statistical difference was observed between different groups for Wallerian degeneration (P = 0.28 at day 14 and P = 0.22 at day 28) and perineural inflammation (P = 0.9 at day 14). Motor and sensory block durations were tested for each group. A statistical difference was observed for motor block duration between the RDPN group (150 minutes [127-172 minutes]), the RDS group (120 minutes [90-120 minutes]), and the R group (60 minutes [60-90 minutes]). Sensory block duration was also statistically different: 660 minutes (660-720 minutes) in the RDPN group, 480 minutes (427-660 minutes) in RDS group, 330 minutes (240-410) in the R group. CONCLUSIONS: A combination of ropivacaine and perineural dexamethasone allows longer sensory block duration compared with ropivacaine alone or ropivacaine and systemic dexamethasone, without increased neural toxicity.

Cache-enabled small cell networks: modeling and tradeoffs.

We consider a network model where small base stations (SBSs) have caching capabilities as a means to alleviate the backhaul load and satisfy users' demand. The SBSs are stochastically distributed over the plane according to a Poisson point process (PPP) and serve their users either (i) by bringing the content from the Internet through a finite rate backhaul or (ii) by serving them from the local caches. We derive closed-form expressions for the outage probability and the average delivery rate as a function of the signal-to-interference-plus-noise ratio (SINR), SBS density, target file bitrate, storage size, file length, and file popularity. We then analyze the impact of key operating parameters on the system performance. It is shown that a certain outage probability can be achieved either by increasing the number of base stations or the total storage size. Our results and analysis provide key insights into the deployment of cache-enabled small cell networks (SCNs), which are seen as a promising solution for future heterogeneous cellular networks.