Brain network decoupling with increased serum neurofilament and reduced cognitive function in Alzheimer's disease

Neurofilament light chain, a putative measure of neuronal damage, is measurable in blood and CSF and is predictive of cognitive function in individuals with Alzheimer's disease. There has been limited prior work linking neurofilament light and functional connectivity, and no prior work has investigated neurofilament light associations with functional connectivity in autosomal dominant Alzheimer's disease. Here, we assessed relationships between blood neurofilament light, cognition, and functional connectivity in a cross-sectional sample of 106 autosomal dominant Alzheimer's disease mutation carriers and 76 non-carriers. We employed an innovative network-level enrichment analysis approach to assess connectome-wide associations with neurofilament light. Neurofilament light was positively correlated with deterioration of functional connectivity within the default mode network and negatively correlated with connectivity between default mode network and executive control networks, including the cingulo-opercular, salience, and dorsal attention networks. Further, reduced connectivity within the default mode network and between the default mode network and executive control networks was associated with reduced cognitive function. Hierarchical regression analysis revealed that neurofilament levels and functional connectivity within the default mode network and between the default mode network and the dorsal attention network explained significant variance in cognitive composite scores when controlling for age, sex, and education. A mediation analysis demonstrated that functional connectivity within the default mode network and between the default mode network and dorsal attention network partially mediated the relationship between blood neurofilament light levels and cognitive function. Our novel results indicate that blood estimates of neurofilament levels correspond to direct measurements of brain dysfunction, shedding new light on the underlying biological processes of Alzheimer's disease. Further, we demonstrate how variation within key brain systems can partially mediate the negative effects of heightened total serum neurofilament levels, suggesting potential regions for targeted interventions. Finally, our results lend further evidence that low-cost and minimally invasive blood measurements of neurofilament may be a useful marker of brain functional connectivity and cognitive decline in Alzheimer's disease.

Soluble TREM2 in CSF and its association with other biomarkers and cognition in autosomal-dominant Alzheimer's disease: a longitudinal observational study

BACKGROUND

Therapeutic modulation of TREM2-dependent microglial function might provide an additional strategy to slow the progression of Alzheimer's disease. Although studies in animal models suggest that TREM2 is protective against Alzheimer's pathology, its effect on tau pathology and its potential beneficial role in people with Alzheimer's disease is still unclear. Our aim was to study associations between the dynamics of soluble TREM2, as a biomarker of TREM2 signalling, and amyloid β (Aβ) deposition, tau-related pathology, neuroimaging markers, and cognitive decline, during the progression of autosomal dominant Alzheimer's disease.

METHODS

We did a longitudinal analysis of data from the Dominantly Inherited Alzheimer Network (DIAN) observational study, which includes families with a history of autosomal dominant Alzheimer's disease. Participants aged over 18 years who were enrolled in DIAN between Jan 1, 2009, and July 31, 2019, were categorised as either carriers of pathogenic variants in PSEN1, PSEN2, and APP genes (n=155) or non-carriers (n=93). We measured amounts of cleaved soluble TREM2 using a novel immunoassay in CSF samples obtained every 2 years from participants who were asymptomatic (Clinical Dementia Rating [CDR]=0) and annually for those who were symptomatic (CDR>0). CSF concentrations of Aβ40, Aβ42, total tau (t-tau), and tau phosphorylated on threonine 181 (p-tau) were measured by validated immunoassays. Predefined neuroimaging measurements were total cortical uptake of Pittsburgh compound B PET (PiB-PET), cortical thickness in the precuneus ascertained by MRI, and hippocampal volume determined by MRI. Cognition was measured using a validated cognitive composite (including DIAN word list test, logical memory delayed recall, digit symbol coding test [total score], and minimental status examination). We based our statistical analysis on univariate and bivariate linear mixed effects models.

FINDINGS

In carriers of pathogenic variants, a high amyloid burden at baseline, represented by low CSF Aβ42 (β=-4·28 × 10-2 [SE 0·013], p=0·0012), but not high cortical uptake in PiB-PET (β=-5·51 × 10-3 [0·011], p=0·63), was the only predictor of an augmented annual rate of subsequent increase in soluble TREM2. Augmented annual rates of increase in soluble TREM2 were associated with a diminished rate of decrease in amyloid deposition, as measured by Aβ42 in CSF (r=0·56 [0·22], p=0·011), in presymptomatic carriers of pathogenic variants, and with diminished annual rate of increase in PiB-PET (r=-0·67 [0·25], p=0·0060) in symptomatic carriers of pathogenic variants. Presymptomatic carriers of pathogenic variants with annual rates of increase in soluble TREM2 lower than the median showed a correlation between enhanced annual rates of increase in p-tau in CSF and augmented annual rates of increase in PiB-PET signal (r=0·45 [0·21], p=0·035), that was not observed in those with rates of increase in soluble TREM2 higher than the median. Furthermore, presymptomatic carriers of pathogenic variants with rates of increase in soluble TREM2 above or below the median had opposite associations between Aβ42 in CSF and PiB-PET uptake when assessed longitudinally. Augmented annual rates of increase in soluble TREM2 in presymptomatic carriers of pathogenic variants correlated with decreased cortical shrinkage in the precuneus (r=0·46 [0·22]), p=0·040) and diminished cognitive decline (r=0·67 [0·22], p=0·0020).

INTERPRETATION

Our findings in autosomal dominant Alzheimer's disease position the TREM2 response within the amyloid cascade immediately after the first pathological changes in Aβ aggregation and further support the role of TREM2 on Aβ plaque deposition and compaction. Furthermore, these findings underpin a beneficial effect of TREM2 on Aβ deposition, Aβ-dependent tau pathology, cortical shrinkage, and cognitive decline. Soluble TREM2 could, therefore, be a key marker for clinical trial design and interpretation. Efforts to develop TREM2-boosting therapies are ongoing.

FUNDING

German Research Foundation, US National Institutes of Health.

Antimicrobial resistance and virulence profiles of Enterobacterales isolated from two-finger and three-finger sloths (Choloepus hoffmanni and Bradypus variegatus) of Costa Rica

Background

Wildlife has been recently recognized as an environmental reservoir for antimicrobial resistance (AMR). However, less information on this topic is available in animals released back into the wild after rehabilitation in wildlife facilities, compared with studies performed exclusively in captive or free-ranging wildlife. This study aimed to evaluate the potential influence of captivity and/or treatment while in captivity of wild sloths on the AMR and virulence profiles of sloths' Enterobacterales.

Methods

Oral and rectal swab samples were collected from 39 two-finger (Choloepus hoffmanni) and three-finger sloths (Bradypus variegatus) of Costa Rica (n = 78) and analyzed using conventional bacteriological techniques. A generalized linear mixed model was applied to estimate the isolates' multiple antimicrobial resistance and virulence indices as a function of animal status.

Results

A considerable level of resistance was detected, especially for Citrobacter youngae and Escherichia coli, with 17.5% of isolates classified as multidrug-resistant. Virulence indices of isolates from rehabilitated sloths were significantly higher than the ones from sloths being hand-reared for shorter periods.

Conclusions

To our knowledge, this is the first description of sloths' antimicrobial resistant Enterobacterales, suggesting that sloths' rehabilitation and consequent exposure to humans, may promote the selection of bacteria with higher virulence. Ultimately, these bacteria may represent a threat to human and animal health due to their zoonotic potential and AMR and virulence profiles.

Influence of Nisin-Biogel at Subinhibitory Concentrations on Virulence Expression in Staphylococcus aureus Isolates from Diabetic Foot Infections

A new approach to diabetic foot infections (DFIs) has been investigated, using a nisin-biogel combining the antimicrobial peptide (AMP) nisin with the natural polysaccharide guar-gum. Since in in vivo conditions bacteria may be exposed to decreased antimicrobial concentrations, known as subinhibitory concentrations (sub-MICs), effects of nisin-biogel sub-MIC values corresponding to 1/2, 1/4 and 1/8 of nisin's minimum inhibitory concentration (MIC) on virulence expression by six Staphylococcus aureus DFI isolates was evaluated by determining bacteria growth rate; expression of genes encoding for staphylococcal protein A (spA), coagulase (coa), clumping factor A (clfA), autolysin (atl), intracellular adhesin A (icaA), intracellular adhesin D (icaD), and the accessory gene regulator I (agrI); biofilm formation; Coa production; and SpA release. Nisin-biogel sub-MICs decreased bacterial growth in a strain- and dose-dependent manner, decreased agrI, atl and clfA expression, and increased spA, coa, icaA and icaD expression. Biofilm formation increased in the presence of nisin-biogel at 1/4 and 1/8 MIC, whereas 1/2 MIC had no effect. Finally, nisin-biogel at sub-MICs did not affect coagulase production, but decreased SpA production in a dose-dependent manner. Results highlight the importance of optimizing nisin-biogel doses before proceeding to in vivo trials, to reduce the risk of virulence factor's up-regulation due to the presence of inappropriate antimicrobial concentrations.

Spatiotemporal accumulation of fatal pharyngeal entrapment of flatfish in harbour porpoises (Phocoena phocoena) in the German North Sea

The evolution of a permanent separation of the upper respiratory and digestive tract is one of the adaptions cetaceans evolved for their aquatic life. Generally, it prevents odontocetes from choking on either saltwater or foreign bodies during ingestion under water. Nevertheless, several sporadic single case reports from different parts of the world show that this separation can be reversed especially by overly large items of prey. This incident can have a fatal outcome for the odontocetes. The German federal state of Schleswig-Holstein has a year-round, permanent and systematic stranding network that retrieves stranded marine mammals from its shorelines and constantly enables post-mortem examinations. In 2016, with nine affected animals, a high incidence of fatal pharyngeal entrapment of flatfish in harbour porpoises (Phocoena phocoena) occurred during spring and early summer on the German North Sea island of Sylt. All flatfish were identified as common sole (Solea solea). A retrospective post-mortem data analysis over a 30-year period from the North and Baltic Sea revealed similar yearly and seasonally case accumulations on the same island in the 1990s as well as several single case events over the whole timespan. All cases except one were caused by flatfish. When flatfish speciation was performed, only common sole was identified. From 1990 to 2019, of all examined harbour porpoises, 0.3% (2/713) from the Baltic Sea and 5.5% (45/820) from the North Sea died due to fish entrapped in the pharynx. On the North Sea coast, the occurrence of fatal obstruction shows high yearly variations from 0 to 33.3%. Years that stand out are especially 1990 to 1992, 1995, as well as 2016. The majority of all cases generally occurred between April and July, indicating also a seasonality of cases. This study evaluates the occurrence of fatal pharyngeal entrapment of fish in two geographically separated harbour porpoise populations. Additionally, common sole is clearly identified as a potentially risky item of prey for these small odontocetes.

Highly Pathogenic Avian Influenza A(H5N8) Virus in Gray Seals, Baltic Sea

We detected a highly pathogenic avian influenza A(H5N8) virus in lung samples of 2 gray seals (Halichoerus grypus) stranded on the Baltic coast of Poland in 2016 and 2017. This virus, clade 2.3.4.4 B, was closely related to avian H5N8 viruses circulating in Europe at the time.

Asymptomatic carriage of antibiotic-resistant Gram-positive cocci among different background populations in East Timor, Southeast Asia

Dissemination of pathogenic multiresistant bacteria is of public health concern. Reliable data can be difficult to obtain, especially in developing countries. This work aimed to characterize the skin and oropharyngeal microbiota, as well as their antimicrobial resistance profiles, of East-Timor populations to identify potentially pathogenic Gram-positive cocci. In order to assess the prevalence of pathogenic bacteria in East-Timor, the oropharyngeal and skin microbiota of 74 individuals was characterized. Gram-positive cocci were evaluated and their antimicrobial resistance profiles were determined. A total of 228 oropharyngeal and 278 skin samples were obtained. The population consisted of 36.5% of asymptomatic carriers of Gram-positive cocci. Kocuria rosea (n = 7, 19.4%), Staphylococcus spp. (n = 6, 16.7%), and Micrococcus luteus (n = 6, 16.7%) were isolated, among others. Antimicrobial resistance levels ranged between 0% and 36.1%, and a multiresistance profile was observed in one third of the isolates. Gram-positive cocci colonization was associated with age group. Prevalence of multiresistant isolates was higher in males who were sampled at the refugee camp. Results show that the prevalence of antimicrobial resistance on East Timor may be underestimated. This study represents the first step toward the full characterization of potential pathogenic Gram-positive cocci present in the populations from East Timor.

A Neurologist's Hard Day's Work: Impact of Inpatient Neurology Consultation in a Tertiary Hospital

INTRODUCTION

Consultation of hospitalized patients under the responsibility of other specialties is a very demanding work. However, it is often under-recognized and poorly documented. The aim of the present study was to assess the burden of the inpatient neurology consultation in a Portuguese hospital and to evaluate the performance of our Neurology department regarding this issue.

MATERIAL AND METHODS

A retrospective study was conducted during 2013, reviewing clinical and demographic data.

RESULTS

Over one year, the neurologists of our department evaluated 632 inpatients. The commonest reasons for consultation were altered mental state/behavior, focal neurological deficit and seizures. Requests came mainly from medical departments but also from Intermediate and Intensive Care Units. Neurologists suggested further investigation in almost one half of patients and management changes in a similar proportion of patients. A new diagnosis could be established in 63% of cases and the most frequent diagnosis were neurological manifestations of systemic disorders, epilepsy and cerebrovascular disease. Our intervention had impact on the care of 68% of patients.

DISCUSSION AND CONCLUSION

Different studies in the literature support our findings and highlight the economic and patient care benefits of this activity. Our results suggest that neurological inpatient observation generates useful interventions for the clinical management of these patients.

Meconium aspiration syndrome - the experience of a tertiary center

BACKGROUND

Approximately 5 % of infants born with a meconium-stained amniotic fluid (MSAF) develop meconium aspiration syndrome (MAS).

AIM

The aims of this study were to analyse demographic data, morbidity and mortality associated with MAS and to identify possible risk factors.

METHODS

Retrospective chart review of newborns with MAS delivered at a tertiary centre from January 1st, 1997 to December 31st, 2008.

RESULTS

MAS was responsible for 1.4 % of all Neonatal Intensive Care Unit (NICU) admissions, with a trend towards a decreasing incidence during the study duration, especially in the cases of thin meconium. Seventy two newborns were analysed during the study period: 55.6 % (n = 40) were of the female gender, 62.5 % were delivered by caesarean section, 93 % had > 36 weeks of gestational age and 91.2 % had a birth weight over 2500g. Sixty-nine percent had an Apgar score < 7 at 1 minute and 23.6 % an Apgar score < 7 at 5 minutes; foetal bradicardia was present in 26.4 % of the newborns and tachycardia in 1.4 %. The presence of meconium was associated with severe asphyxia and carried a bad prognosis with an increased risk of developing hypoxia (58.3 %), need of mechanical ventilatory support (43.1 %), respiratory and/or metabolic acidosis (30.6 %), pulmonary hypertension (11.1 %) and hypoxic ischemic encephalopathy (29.2 %). The mortality rate was 2.8 %. Thick meconium was associated with higher morbidity and mortality rates.

CONCLUSION

The number of admissions for MAS has been decreasing mostly because of a lower admission rate due to thin meconium; the number of cases with thick meconium has remained constant throughout the years. An Apgar score < 7 at 1 minute and signs of foetal distress during labour were associated with MAS. The MAS related morbidity remains significant.