Detection of polymyxins resistance among Enterobacterales: evaluation of available methods and proposal of a new rapid and feasible methodology.

BACKGROUND: Fast and accurate detection of polymyxins resistance is necessary as they remain the last resources to treat infections caused by Carbapenem-resistant Enterobacterales in many regions. We evaluated the rapid colorimetric polymyxin B elution (RCPE) and developed its miniaturized version, RCPE microelution (RCPEm), aiming to detect polymyxins resistance among Enterobacterales. METHODS: The methodologies consist of exposing the bacterial population in a solution (NP solution) where polymyxin B disks were previously eluted to obtain a concentration of 2 µg/mL for RCPE and 3 µg/mL for RCPEm. RESULTS: Two hundred sixty-seven Enterobacterales were evaluated, 90 (33.7%) resistant to polymyxin B by broth microdilution. It was observed 0.6% of major error (ME) by RCPE, with a specificity of 99.4%. The miniaturized version (RCPEm) presented the same ME and specificity values, but slightly higher sensitivity (97.8% vs. 95.6%) with 2.2% of very major error (VME). CONCLUSIONS: RCPE and RCPEm proved to be useful alternatives to determine polymyxin B susceptibility in clinical microbiology laboratories, presenting low cost, being easy to perform, and demanding short incubation time.

Hippocampal plasticity mechanisms mediating experience-dependent learning change over time.

The requirement of NMDA receptor (NMDAR) activity for memory formation is well described. However, the plasticity mechanisms for memory can be modified by experience, such that a future similar learning becomes independent of NMDARs. This effect has often been reported in learning events conducted with a few days interval. In this work, we asked whether the NMDAR-independency is permanent or the brain regions and plasticity mechanisms of experience-dependent learning may change over time. Considering that contextual memories undergo a gradual reorganization over time, becoming progressively independent from the hippocampus and dependent upon cortical regions, we investigated the brain regions mediating a new related learning conducted at a remote time-point, when the first memory was already cortically established. First, we demonstrated that anterior cingulate cortex was not able to support a learning subsequent to a previous systems-level consolidated memory; it did require at least one functional subregion of the hippocampus (ventral or dorsal). Moreover, after replicating findings showing that a few days interval between trainings induces a NMDAR-independent learning, we managed to show that a learning following a longer interval once again becomes dependent on NMDARs in the hippocampus. These findings suggest that while the previous memory grows independent from the hippocampus over time, an experience-dependent learning following a systems-consolidated memory once again engages the hippocampus and a NMDAR-dependent plasticity mechanism.

Switching from high-fat feeding (HFD) to regular diet improves metabolic and behavioral impairments in middle-aged female mice.

Obesity represents a risk factor for metabolic syndrome and cardiovascular and psychiatric disorders. Excessive caloric intake, particularly in dietary fats, is an environmental factor that contributes to obesity development. Thus, the observation that switching from long-standing dietary obesity to standard diet (SD) can ameliorate the high-fat diet-induced metabolic, memory, and emotionality-related impairments are particularly important. Herein we investigated whether switching from the high-fat diet (HFD) to SD could improve the metabolic and behavioral impairments observed in middle-aged females C57Bl/6 mice. During twelve weeks, the animals received a high-fat diet (61 % fat) or SD diet. After 12-weeks, the HFD group's diet was switched to SD for an additional four weeks. It was observed a progressive deleterious effect of HFD in metabolic and behavioral parameters in mice. After four weeks of HFD-feeding, the animals showed glucose intolerance and increased locomotor activity. A subsequent increase in the body mass gain, hyperglycemia, and depressive-like behavior was observed after eight weeks, and memory impairments after twelve weeks. After replacing the HFD to SD, it was observed an improvement of metabolic (loss of body mass, normal plasma glucose levels, and glucose tolerance) and behavioral (absence of memory and emotional alterations) parameters. These results demonstrate the temporal development of metabolic and behavioral impairments following HFD in middle-age female mice and provide new evidence that these alterations can be improved by switching back the diet to SD.

A selanylimidazopyridine (3-SePh-IP) reverses the prodepressant- and anxiogenic-like effects of a high-fat/high-fructose diet in mice.

OBJECTIVE: While chronic feeding with high-fat or high-sugar diets is known related to obesity and type 2 diabetes, later data have indicated that it is also related to depression and anxiety appearance. In this regard, multi-target drugs raise considerable interest as promising therapeutic solutions to complex diseases. Considering the pharmacological effects of the imidazopyridine-derivative moiety imidazo[1,2-a]pyridine and the organoselenium molecules, the combination of both could be a feasible strategy to develop efficient drugs to handle obesity and related comorbidities, for example dyslipidemia and mood disorders. METHODS: The antidepressant- and anxiolytic-like properties of a selanylimidazopyridine compound, 2-Phenyl-3-(phenylselanyl)imidazo[1,2-a]pyridine (3-SePh-IP), were evaluated on high-fat/high-fructose diet (HFFD)-fed female Swiss mice. KEY FINDINGS: Our results showed that a short-term HFFD (16 days) could promote a significant body weight gain, hypercholesterolemia, glucose intolerance, and anxiety- and depressive-like behaviour in mice. Concomitant treatment with 3-SePh-IP (10 mg/kg; i.p.) attenuated the HFFD-induced increase in cholesterol levels and blunted the anxiety- and depressive-like behaviour in mice. CONCLUSIONS: 3-SePh-IP holds multimodal pharmacological properties, which provide a rationale for further studies, for example to assess the underlying mechanisms linked to its anxiolytic- and antidepressive-like activities.

Impact of different fructose concentrations on metabolic and behavioral parameters of male and female mice.

Clinical evidence has shown that a high consumption of sugar-sweetened beverages is a risk factor for developing obesity and metabolic syndrome. There has also been increasing interest in the potential effects of high-fructose intake on behavior. The present study evaluated sex differences in behavioral and metabolic characteristics in response to chronic fructose intake in mice. Swiss mice (3-months-old) had access to tap water or fructose-water solution (at 15% or 30% w/v) ad libitum for nine weeks. After the 8 weeks, the mice were submitted to a battery of behavioral tests. A glucose tolerance test was performed one day after these behavioral tests, and the next day blood was collected for biochemical analysis. At a 15% concentration, fructose-intaking resulted in higher plasma cholesterol levels and glucose intolerance in mice that paralleled with a passive stress-coping behavior in the female mice and lower self-care behavior in the male and the female mice. At a 30% concentration, fructose-intaking resulted in higher body mass gain and higher plasma cholesterol and triglycerides levels in the male and the female mice, whereas glucose intolerance was more pronounced in the male mice. Spatial memory impairments and lower self-care behavior were observed in the male and the female mice, while passive stress-coping behavior was observed only in the female mice. Collectively, high-fructose intake induces metabolic and behavioral alterations in mice, with the males being more susceptible to glucose metabolism dysfunctions and the females to depressive-like endophenotypes.

Left-sided gallbladder (LSG) associated with true diverticulum, a case report.

The left-sided gallbladder (LSG) is a rare type of anatomical variation (ectopia) defined by the location of the bladder to the left side of the liver falciform and round ligaments. Initially reported in 1886 by Hochstetter, the finding is usually accidental since it is mostly an asymptomatic condition, thus not causing the patient any harm and being few reported cases in the current literature. Surgical cases are most associated with gallstones such as presented in this case report. Our patient was a 60-year-old man from Manaus who presented with symptomatic acute cholelithiasis submitted to laparoscopic cholecystectomy which allowed the visualization of true LSG concomitant with a polyp suggestive lesion. A diagnosis post-cholecystectomy of true gallbladder diverticulum was confirmed by histopathological analysis. Being one of three types of LSG, true LSG is more associated with other structural changes in the biliary tree and also some liver changes, in our case we identified no such alterations. True gallbladder diverticulum has, as the main characteristic, the herniation of all tissues of the gallbladder wall. When presented with LSG, is important to correctly identify the altered structures and adjust the surgical technique in the best way possible, it is up to the surgeon to adapt to the situation presented and ensure the best treatment for his patient.

Behavioural, metabolic and neurochemical effects of environmental enrichment in high-fat cholesterol-enriched diet-fed mice.

While chronic high-fat feeding has long been associated with the rising incidence of obesity/type 2 diabetes, recent evidence has established that it is also associated with deficits in hippocampus-dependent memory. In this regard, environmental enrichment (EE) is an animal housing technique composed of increased space, physical activity, and social interactions, which in turn increases sensory, cognitive, motor, and social stimulation. EE leads to improved cerebral health as defined by increased neurogenesis, enhanced learning and memory and resistance to external cerebral insults. In the present study, the impacts of environmental enrichment (EE) on Swiss mice fed a high-fat, cholesterol-enriched diet (HFECD; 20% fat and 1.5% cholesterol) were investigated. Here, we demonstrated that EE, when initiated 4 weeks after the beginning of HFECD in mice, prevents HFECD-induced spatial memory and object recognition impairment, which were tested in T-maze and object recognition tests. Although EE did not affect HFECD-induced weight gain or hypercholesterolaemia, it improved glucose tolerance. On the other hand, EE was unable to mitigate a decrease in brain-derived neurotrophic factor (BDNF) and IL-6 hippocampal levels induced by the HFECD. Overall, while our results reinforce the positive and neuroprotective effects of EE on cognition they do not support a role for EE in preventing the neurochemical changes induced by the HFECD. Based on clinical observations that nondiabetic individuals with mild forms of impaired glucose tolerance have a higher risk of cognitive impairments, one can speculate about the connection between the effects of EE on glucose intolerance and its effects on cognition.

Hypercholesterolemia impairs contextual fear conditioning memory formation in female mice: evidence for cholinergic dysfunction.

The present study evaluated the effects of hypercholesterolemia in response to conditioned aversive stimuli in mice. Specifically, (a) young (3 months old) and aged (24 months old) female C57Bl/6 mice were fed daily for 4 weeks with a standard rodent diet or an enriched cholesterol diet (ECD) and then subjected to the contextual fear conditioning test. In another experimental set, 3-month-old C576Bl/6 female mice, fed daily during the 4 weeks with the standard rodent diet or ECD, were subjected to the contextual fear conditioning test and received vehicle or scopolamine (0.37 mg/kg; intraperitoneally) immediately after the training session. (b) 12-month-old C576Bl/6 and low-density lipoprotein receptor knockout mice (LDLr) female mice were subjected to the contextual fear conditioning test. In another experimental set, they were subjected to the contextual fear conditioning test and received vehicle or donepezil (3.0 mg/kg; intraperitoneally) immediately after the training session. The present results show that (a) the ECD specifically impaired retrieval of contextual fear memory in aged mice; (b) an ineffective dose of scopolamine impaired fear memory consolidation in young mice fed the ECD; (c) LDLr mice presented impaired contextual fear memory retrieval; and (d) boosting cholinergic neurotransmission with a single donepezil administration at the consolidation window led to improved fear memory consolidation in LDLr mice. These findings suggest that high levels of cholesterol induced by either an ECD or a genetic deletion of LDLr decreased freezing behavior on the contextual fear conditioning test, which seemed to involve dysfunction of the cholinergic system.

Enhancement of extinction memory by pharmacological and behavioral interventions targeted to its reactivation.

Extinction is a process that involves new learning that inhibits the expression of previously acquired memories. Although temporarily effective, extinction does not erase an original fear association. Since the extinction trace tends to fade over time, the original memory can resurge. On the other hand, strengthening effects have been described in several reconsolidation studies using different behavioral and pharmacological manipulations. In order to know whether an extinction memory can be strengthened by reactivation-based interventions in the contextual fear conditioning task, we began by replicating the classic phenomenon of spontaneous recovery to show that brief reexposure sessions can prevent the decay of the extinction trace over time in a long-lasting way. This fear attenuation was shown to depend both on L-type calcium channels and protein synthesis, which suggests a reconsolidation process behind the reactivation-induced strengthening effect. The extinction trace was also susceptible to enhancement by a post-reactivation infusion of a memory-enhancing drug (NaB), which was also able to prevent rapid fear reacquisition (savings). These findings point to new reactivation-based approaches able to strengthen an extinction memory to promote its persistence. The constructive interactions between extinction and reconsolidation may represent a promising novel approach in the realm of fear-related disorder treatments.

Influence of radiopacifying agents on the solubility, pH and antimicrobial activity of portland cement.

The aim of this study was to evaluate the interference of the radiopacifiers bismuth oxide (BO), bismuth carbonate (BC), bismuth subnitrate (BS), and zirconiun oxide (ZO) on the solubility, alkalinity and antimicrobial properties of white Portland cement (WPC). The substances were incorporated to PC, at a ratio of 1:4 (v/v) and subjected to a solubility test. To evaluate the pH, the cements were inserted into retrograde cavities prepared in simulated acrylic teeth and immediately immersed in deionized water. The pH of the solution was measured at 3, 24, 72 and 168 h. The antimicrobial activity was evaluated by a radial diffusion method against the microorganisms S. aureus (ATCC 25923), P. aeruginosa (ATCC 27853), E. faecalis (ATCC 29212) and C. albicans (ATCC 10231). The zone of microbial growth inhibition was measured after 24 h. The addition of BS and BC increased the solubility of the cement. The pH values demonstrated that all materials produced alkaline levels. At 3 h, BS showed lower pH than WPC (p<0.05). At 168 h, all materials showed similar pHs (p>0.05). The materials did not present antimicrobial activity for S. aureus, P. aeruginosas and E. faecalis (p>0.05). With regards to C. albicans, all materials formed an inhibition zone, mainly the mixture of WPC with ZO (p<0.05). The type of radiopacifier incorporated into WPC interfered with its physical and antimicrobial properties. ZO was found to be a viable radiopacifier that can be used with WPC.

Influence of radiopacifying agents on the solubility, pH and antimicrobial activity of portland cement

The aim of this study was to evaluate the interference of the radiopacifiers bismuth oxide (BO), bismuth carbonate (BC), bismuth subnitrate (BS), and zirconiun oxide (ZO) on the solubility, alkalinity and antimicrobial properties of white Portland cement (WPC). The substances were incorporated to PC, at a ratio of 1:4 (v/v) and subjected to a solubility test. To evaluate the pH, the cements were inserted into retrograde cavities prepared in simulated acrylic teeth and immediately immersed in deionized water. The pH of the solution was measured at 3, 24, 72 and 168 h. The antimicrobial activity was evaluated by a radial diffusion method against the microorganisms S. aureus (ATCC 25923), P. aeruginosa (ATCC 27853), E. faecalis (ATCC 29212) and C. albicans (ATCC 10231). The zone of microbial growth inhibition was measured after 24 h. The addition of BS and BC increased the solubility of the cement. The pH values demonstrated that all materials produced alkaline levels. At 3 h, BS showed lower pH than WPC (p<0.05). At 168 h, all materials showed similar pHs (p>0.05). The materials did not present antimicrobial activity for S. aureus, P. aeruginosas and E. faecalis (p>0.05). With regards to C. albicans, all materials formed an inhibition zone, mainly the mixture of WPC with ZO (p<0.05). The type of radiopacifier incorporated into WPC interfered with its physical and antimicrobial properties. ZO was found to be a viable radiopacifier that can be used with WPC.