Impact of infections on long-term outcome after severe middle cerebral artery infarction

Seizure prediction in stroke survivors who experienced an infection at skilled nursing facilities-a machine learning approach

Background

Infections and seizures are some of the most common complications in stroke survivors. Infections are the most common risk factor for seizures and stroke survivors that experience an infection are at greater risk of experiencing seizures. A predictive model to determine which stroke survivors are at the greatest risk for a seizure after an infection can be used to help providers focus on prevention of seizures in higher risk residents that experience an infection.

Methods

A predictive model was generated from a retrospective study of the Long-Term Care Minimum Data Set (MDS) 3.0 (2014-2018, n = 262,301). Techniques included three data balancing methods (SMOTE for up sampling, ENN for down sampling, and SMOTEENN for up and down sampling) and three feature selection methods (LASSO, Recursive Feature Elimination, and Principal Component Analysis). One balancing and one feature selection technique was applied, and the resulting dataset was then trained on four machine learning models (Logistic Regression, Random Forest, XGBoost, and Neural Network). Model performance was evaluated with AUC and accuracy, and interpretation used SHapley Additive exPlanations.

Results

Using data balancing methods improved the prediction performances of the machine learning models, but feature selection did not remove any features and did not affect performance. With all models having a high accuracy (76.5%-99.9%), interpretation on all four models yielded the most holistic view. SHAP values indicated that therapy (speech, physical, occupational, and respiratory), independence (activities of daily living for walking, mobility, eating, dressing, and toilet use), and mood (severity score, anti-anxiety medications, antidepressants, and antipsychotics) features contributed the most. Meaning, stroke survivors who received fewer therapy hours, were less independent, had a worse overall mood were at a greater risk of having a seizure after an infection.

Conclusion

The development of a tool to predict seizure following an infection in stroke survivors can be interpreted by providers to guide treatment and prevent complications long term. This promotes individualized treatment plans that can increase the quality of resident care.

Incidence, risk factors and microbiological aetiology of urinary tract infections in admitted stroke patients at a teaching hospital in Zimbabwe: A prospective cohort study

Background and purpose

The occurrence of urinary tract infections (UTIs) after stroke is a well recognised complication. The aim of this study was to determine the incidence of UTIs in stroke patients admitted at a teaching hospital in Zimbabwe.

Methods

A prospective cohort study was conducted in stroke patients admitted within 7 days from onset of stroke. Patients were followed up throughout the admission period and those with symptomatic UTI were identified. Urine samples for analysis were collected and causative bacterial organisms were identified with their antibiotic susceptibility patterns analysed.

Results

A total of 145 stroke patients were followed up during their in-patient care. 28 patients (19.3%) developed a urinary tract infection, 45 patients (31%) had asymptomatic bacteriuria and 72 patients (49.7%) had no bacteriuria. The median time from admission to UTI occurrence post stroke was 5 (IQR 4–7) days. Severe stroke (NIHSS score 16–42) was an independent risk factor for UTI development with an odds ratio (OR) 5.15 (1.68–15.75) p<0.001.The commonest bacterial causative organisms cultured were Escherichia coli (27.6%) ; Klebsiella species (21.1%) and Enterococcus faecalis (19.7%). Twenty nine percent of the cultured Gram negative bacteria were extended-spectrum beta-lactamase (ESBL) producers.

Conclusions

UTIs are common in admitted stroke patients and a significant percentage of causative organisms are multi-drug resistant. UTI occurrence is more common in patients with severe stroke and is associated with increased hospital stay. These observations highlight the need for robust infection prevention and control strategies to curb this common post-stroke complication.

Temporal Profile of Pneumonia After Stroke

Supplemental Digital Content is available in the text.

The occurrence of pneumonia after stroke is associated with a higher risk of poor outcome or death. We assessed the temporal profile of pneumonia after stroke and its association with poor outcome at several time points to identify the most optimal period for testing pneumonia prevention strategies.

Targeting the Immune System for Ischemic Stroke

Stroke is responsible for almost 6 million deaths and more than 10% of all mortalities each year, and two-thirds of stroke survivors remain disabled. With treatments for ischemic stroke still limited to clot lysis and/or mechanical removal, new therapeutic targets are desperately needed. In this review, we provide an overview of the complex mechanisms of innate and adaptive immune cell-mediated inflammatory injury, that exacerbates infarct development for several days after stroke. We also highlight the features of poststroke systemic immunodepression that commonly leads to infections and some mortalities, and argue that safe and effective therapies will need to balance pro- and anti-inflammatory mechanisms in a time-sensitive manner, to maximize the likelihood of an improved long-term outcome.

Association Between Common Infections and Incident Post-Stroke Dementia: A Cohort Study Using the Clinical Practice Research Datalink

PURPOSE

To investigate the association between common infections and post-stroke dementia in a UK population-based cohort.

MATERIALS AND METHODS

A total of 60,392 stroke survivors (51.2% male, median age 74.3 years, IQR 63.9-82.4 years) were identified using primary care records from the Clinical Practice Research Datalink (CPRD) linked to Hospital Episode Statistics (HES) with no history of dementia. Primary exposure was any GP-recorded infection (lower respiratory tract infection (LRTI), urinary tract infection (UTI) requiring antibiotics, skin and soft tissue infection requiring antibiotics) occurring after stroke. The primary outcome was incident all-cause dementia recorded in primary care records. In sensitivity analyses, we restricted to individuals with linked hospital records and expanded definitions to include ICD-10 coded hospital admissions. We used multivariable Cox regression to investigate the association between common infections and dementia occurring from 3 months to 5 years after stroke.

RESULTS

Of 60,392 stroke survivors, 20,969 (34.7%) experienced at least one infection and overall 4512 (7.5%) developed dementia during follow-up. Early dementia (3 months to 1-year post-stroke) risk was increased in those with at least one GP-recorded infection (HR 1.44, 95% CI 1.21-1.71), with stronger associations when hospitalised infections were included (HR 1.84, 95% CI 1.58-2.14). Late dementia (1-5 years) was only associated with hospitalised, but not with GP-recorded, infections.

CONCLUSION

There was evidence of an association between common infections and post-stroke dementia, strongest in the 3-12 months following stroke. Better understanding of this relationship could help inform knowledge of pathways to dementia post-stroke and targeting of preventive interventions.

Biomarkers of immune capacity, infection and inflammation are associated with poor outcome and mortality after stroke - the PREDICT study

Background

Almost 40% of stroke patients have a poor outcome at 3 months after the index event. Predictors for stroke outcome in the early acute phase may help to tailor stroke treatment. Infection and inflammation are considered to influence stroke outcome.

Methods

In a prospective multicenter study in Germany and Spain, including 486 patients with acute ischemic stroke, we used multivariable regression analysis to investigate the association of poor outcome with monocytic HLA-DR (mHLA-DR) expression, interleukin 6 (IL-6), interleukin 10 (IL-10), tumor necrosis factor alpha (TNF-alpha) and lipopolysaccharide-binding protein (LBP) as markers for immunodepression, inflammation and infection. Outcome was assessed at 3 months after stroke via a structured telephone interview using the modified Rankin Scale (mRS). Poor outcome was defined as a mRS score of 3 or higher which included death. Furthermore, a time-to-event analysis for death within 3 months was performed.

Results

Three-month outcome data was available for 391 patients. Female sex, older age, diabetes mellitus, atrial fibrillation, stroke-associated pneumonia (SAP) and higher National Institute of Health Stroke Scale (NIHSS) score as well as lower mHLA-DR levels, higher IL-6 and LBP-levels at day 1 were associated with poor outcome at 3 months in bivariate analysis. Furthermore, multivariable analysis revealed that lower mHLA-DR expression was associated with poor outcome.

Female sex, older age, atrial fibrillation, SAP, higher NIHSS score, lower mHLA-DR expression and higher IL-6 levels were associated with shorter survival time in bivariate analysis. In multivariable analysis, SAP and higher IL-6 levels on day 1 were associated with shorter survival time.

Conclusions

SAP, lower mHLA-DR-expression and higher IL-6 levels on day one are associated with poor outcome and shorter survival time at 3 months after stroke onset.

Trial registration

www.clinicaltrials.gov, NCT01079728, March 3, 2010.

Infections Up to 76 Days After Stroke Increase Disability and Death

Early infection after stroke is associated with a poor outcome. We aimed to determine whether delayed infections (up to 76 days post-stroke) are associated with poor outcome at 90 days. Data came from the international Efficacy of Nitric Oxide Stroke (ENOS, ISRCTN99414122) trial. Post hoc data on infections were obtained from serious adverse events reports between 1 and 76 days following stroke in this large cohort of patients. Regression models accounting for baseline covariates were used to analyse fatalities and functional outcomes (modified Rankin Scale (mRS), Barthel Index, Euro-Qol-5D) at 90 days, in patients with infection compared to those without infection. Of 4011 patients, 242 (6.0%) developed one or more serious infections. Infections were associated with an increased risk of death (p < 0.001) and an increased likelihood of dependency (measured by mRS) compared to those of all other patients (p < 0.001). This remained when only surviving patients were analysed, indicating that the worsening of functional outcome is not due to mortality (p < 0.001). In addition, the timing of the infection after stroke did not alter its detrimental association with fatality (p = 0.14) or functional outcome (p = 0.47). In conclusion, severe post-stroke infections, whether occurring early or late after stroke, are associated with an increased risk of death and poorer functional outcome, independent of differences in baseline characteristics or treatment. Not only are strategies needed for reducing the risk of infection immediately after stroke, but also during the first 3 months following a stroke. This study is registered: ISRCTN registry, number ISRCTN99414122, ClinicalTrials.gov Identifier, NCT00989716.

Safety and efficacy of natalizumab in patients with acute ischaemic stroke (ACTION): a randomised, placebo-controlled, double-blind phase 2 trial

BACKGROUND

In animal models of acute ischaemic stroke, blocking of the leukocyte-endothelium adhesion by antagonism of α4 integrin reduces infarct volumes and improves outcomes. We assessed the effect of one dose of natalizumab, an antibody against the leukocyte adhesion molecule α4 integrin, in patients with acute ischaemic stroke.

METHODS

In this double-blind, phase 2 study, patients with acute ischaemic stroke (aged 18-85 years) from 30 US and European clinical sites were randomly assigned (1:1) to 300 mg intravenous natalizumab or placebo with stratification by treatment window and baseline infarct size. Patients, investigators, and study staff were masked to treatment assignments. The primary endpoint was the change in infarct volume from baseline to day 5 and was assessed in the modified intention-to-treat population. Secondary endpoints were the change in infarct volume from baseline to day 30, and from 24 h to days 5 and 30; the National Institute of Health Stroke Scale (NIHSS) at baseline, 24 h, and at days 5 (or discharge), 30, and 90; and modified Rankin Scale (mRS) and Barthel Index (BI) at days 5 (or discharge), 30, and 90. This trial is registered with ClinicalTrials.gov, number NCT01955707.

FINDINGS

Between Dec 16, 2013, and April 9, 2015, 161 patients were randomly assigned to natalizumab (n=79) or placebo (n=82). Natalizumab did not reduce infarct volume growth from baseline to day 5 compared with placebo (median absolute growth 28 mL [range -8 to 303] vs 22 mL [-11 to 328]; relative growth ratio 1·09 [90% CI 0·91-1·30], p=0·78) or to day 30 (4 mL [-43 to 121] vs 4 mL [-28 to 180]; 1·05 [0·88-1·27], p=0·68), from 24 h to day 5 (8 mL [-30 to 177] vs 7 mL [-13 to 204]; 1·00 [0·89-1·12], p=0·49), and from 24 h to day 30 (-5 mL [-93 to 81] vs -5 mL [-48 to 48]; 0·98 [0·87-1·11], p=0·40). No difference was noted between the natalizumab and placebo groups in the NIHSS (score ≤1 or ≥8 point improvement) from baseline at 24 h, day 5 (or discharge), day 30 (27 [35%] vs 36 [44%]; odds ratio 0·69 [90% CI 0·39-1·21], p=0·86), and day 90 (36 [47%] vs 37 [46%]; 1·10 [0·63-1·93], p=0·39). More patients in the natalizumab group than in the placebo group had mRS scores of 0 or 1 at day 30 (13 [18%] vs seven [9%]; odds ratio 2·88 [90% CI 1·20-6·93], p=0·024) and day 90 (18 [25%] vs 16 [21%]; 1·48 [0·74-2·98], p=0·18); and BI (score ≥95) at day 90 (34 [44%] vs 26 [33%]; 1·91 [1·07-3·41], p=0·033) but not significantly at day 5 or day 30 (26 [34%] vs 26 [32%]; 1·13 [0·63-2·00], p=0·37). Natalizumab and placebo groups had similar incidences of adverse events (77 [99%] of 78 patients vs 81 [99%] of 82 patients), serious adverse events (36 [46%] vs 38 [46%]), and deaths (14 [18%] vs 13 [16%]). Two patients in the natalizumab group died because of adverse events assessed as related to treatment by the investigator (pneumonia, and septic shock and multiorgan failure).

INTERPRETATION

Natalizumab administered up to 9 h after stroke onset did not reduce infarct growth. Treatment-associated benefits on functional outcomes might warrant further investigation.

FUNDING

Biogen.

Microglia and Monocyte-Derived Macrophages in Stroke

Historically, the brain has been considered an immune-privileged organ separated from the peripheral immune system by the blood-brain barrier. However, immune responses do occur in the brain in neurological conditions in which the integrity of the blood-brain barrier is compromised, exposing the brain to peripheral antigens and endogenous danger signals. While most of the associated pathological processes occur in the central nervous system, it is now clear that peripheral immune cells, especially mononuclear phagocytes, that infiltrate into the injury site play a key role in modulating the progression of primary brain injury development. As inflammation is a necessary and critical component for the subsequent injury resolution process, understanding the contribution of mononuclear phagocytes on the regulation of inflammatory responses may provide novel approaches for potential therapies. Furthermore, predisposed comorbid conditions at the time of stroke cause the alteration of stroke-induced immune and inflammatory responses and subsequently influence stroke outcome. In this review, we summarize a role for microglia and monocytes/macrophages in acute ischemic stroke in the context of normal and metabolically compromised conditions.

Ischemia, Immunosuppression and Infection--Tackling the Predicaments of Post-Stroke Complications

The incidence of stroke has risen over the past decade and will continue to be one of the leading causes of death and disability worldwide. While a large portion of immediate death following stroke is due to cerebral infarction and neurological complications, the most common medical complication in stroke patients is infection. In fact, infections, such as pneumonia and urinary tract infections, greatly worsen the clinical outcome of stroke patients. Recent evidence suggests that the disrupted interplay between the central nervous system and immune system contributes to the development of infection after stroke. The suppression of systemic immunity by the nervous system is thought to protect the brain from further inflammatory insult, yet this comes at the cost of increased susceptibility to infection after stroke. To improve patient outcome, there have been attempts to lessen the stroke-associated bacterial burden through the prophylactic use of broad-spectrum antibiotics. However, preventative antibiotic treatments have been unsuccessful, and therefore have been discouraged. Additionally, with the ever-rising obstacle of antibiotic-resistance, future therapeutic options to reverse immune impairment after stroke by augmentation of host immunity may be a viable alternative option. However, cautionary steps are required to ensure that collateral ischemic damage caused by cerebral inflammation remains minimal.

Antigen-specific immune reactions to ischemic stroke

Brain proteins are detected in the cerebrospinal fluid (CSF) and blood of stroke patients and their concentration is related to the extent of brain damage. Antibodies against brain antigens develop after stroke, suggesting a humoral immune response to the brain injury. Furthermore, induced immune tolerance is beneficial in animal models of cerebral ischemia. The presence of circulating T cells sensitized against brain antigens, and antigen presenting cells (APCs) carrying brain antigens in draining lymphoid tissue of stroke patients support the notion that stroke might induce antigen-specific immune responses. After stroke, brain proteins that are normally hidden from the periphery, inflammatory mediators, and danger signals can exit the brain through several efflux routes. They can reach the blood after leaking out of the damaged blood-brain barrier (BBB) or following the drainage of interstitial fluid to the dural venous sinus, or reach the cervical lymph nodes through the nasal lymphatics following CSF drainage along the arachnoid sheaths of nerves across the nasal submucosa. The route and mode of access of brain antigens to lymphoid tissue could influence the type of response. Central and peripheral tolerance prevents autoimmunity, but the actual mechanisms of tolerance to brain antigens released into the periphery in the presence of inflammation, danger signals, and APCs, are not fully characterized. Stroke does not systematically trigger autoimmunity, but under certain circumstances, such as pronounced systemic inflammation or infection, autoreactive T cells could escape the tolerance controls. Further investigation is needed to elucidate whether antigen-specific immune events could underlie neurological complications impairing recovery from stroke.

Gene expression in peripheral immune cells following cardioembolic stroke is sexually dimorphic

AIMS

Epidemiological studies suggest that sex has a role in the pathogenesis of cardioembolic stroke. Since stroke is a vascular disease, identifying sexually dimorphic gene expression changes in blood leukocytes can inform on sex-specific risk factors, response and outcome biology. We aimed to examine the sexually dimorphic immune response following cardioembolic stroke by studying the differential gene expression in peripheral white blood cells.

METHODS AND RESULTS

Blood samples from patients with cardioembolic stroke were obtained at ≤3 hours (prior to treatment), 5 hours and 24 hours (after treatment) after stroke onset (n = 23; 69 samples) and compared with vascular risk factor controls without symptomatic vascular diseases (n = 23, 23 samples) (ANCOVA, false discovery rate p≤0.05, |fold change| ≥1.2). mRNA levels were measured on whole-genome Affymetrix microarrays. There were more up-regulated than down-regulated genes in both sexes, and females had more differentially expressed genes than males following cardioembolic stroke. Female gene expression was associated with cell death and survival, cell-cell signaling and inflammation. Male gene expression was associated with cellular assembly, organization and compromise. Immune response pathways were over represented at ≤3, 5 and 24 h after stroke in female subjects but only at 24 h in males. Neutrophil-specific genes were differentially expressed at 3, 5 and 24 h in females but only at 5 h and 24 h in males.

CONCLUSIONS

There are sexually dimorphic immune cell expression profiles following cardioembolic stroke. Future studies are needed to confirm the findings using qRT-PCR in an independent cohort, to determine how they relate to risk and outcome, and to compare to other causes of ischemic stroke.