Depressive symptoms are associated with clinical outcomes in heart failure with reduced ejection fraction.

AIMS: The objective of this study was to examine associations between elevated depressive symptoms and increased risk of adverse clinical events patients with heart failure and reduced ejection fraction (HFrEF), as well as the potential contribution of health behaviours. METHODS AND RESULTS: One hundred forty-two men and women with HFrEF were enrolled through heart failure (HF) clinics and followed over time. At baseline and 6 months, depressive symptoms were assessed by the Beck Depression Inventory-II (BDI-II) and HFrEF disease activity by B-type natriuretic peptide (BNP). The Self-Care of Heart Failure Index (SCHFI) was used to assess HF self-care behaviours. Proportional hazards regression models assessed the contribution of depressive symptoms and HFrEF disease biomarkers on death or cardiovascular hospitalization. Over a median follow-up period of 4 years, 42 patients (30%) died, and 84 (60%) had cardiovascular hospitalizations. A 10-point higher baseline BDI-II score was associated with a 35% greater risk of death or cardiovascular hospitalization. Higher baseline BDI-II scores were associated with poorer HF self-care maintenance behaviours (R = -0.30, P < 0.001) and fewer daily steps (R = -0.19, P = 0.04), suggesting that elevated depressive symptoms may diminish important health behaviours. Increases in plasma BNP over 6 months were associated with worse outcomes. Changes in BDI-II and plasma BNP over 6 months were positively related (R = 0.25, P = 0.004). CONCLUSIONS: This study confirms that elevated depressive symptoms are associated with an increased likelihood of adverse clinical outcomes in patients with HFrEF. Poor health behaviours may contribute to the adverse association of elevated depressive symptoms with the increased hazard of adverse clinical outcomes.

Association of Depression Symptoms and Biomarkers of Risk on Clinical Outcomes in HFrEF.

BACKGROUND: Prior studies have demonstrated an association of depression with adverse clinical outcomes in patients with HFrEF, but the possible mechanisms responsible for the association are not unserstood. METHODS: 142 men and women with HFrEF were enrolled through HF clinics and followed over time. At baseline and 6-months, depression was assessed by the Beck Depression Inventory (BDI-II) and disease activity by B-type natriuretic peptide (BNP). Proportional Hazards Regression Models assessed the contribution of depressive symptoms and HFrEF disease biomarkers on death or cardiovascular hospitalization. RESULTS: Over a median follow-up period of 4 years, 42 patients (30%) died, and 84 (60%) had cardiovascular hospitalizations. A 10-point higher baseline BDI-II score was associated with a 35% higher hazard of death or cardiovascular hospitalization. Greater baseline BDI-II scores were associated with poorer HF self-care maintenance (R=-0.30, p<0.001) and fewer daily steps (R=-0.19, p=0.04), suggesting that depression may adversely affect important health behaviors. Increases in plasma BNP over 6 months were associated with worse outcomes. Changes in BDI-II score and plasma BNP over 6 months were positively correlated (R=0.25, p=0.004). CONCLUSIONS: This study underscores the importance of elevated depression symptoms and their association with an increased likelihood of adverse clinical outcomes in patients with HFrEF. Health behaviors may play a greater role than direct biobehavioral pathways in the adverse effects of depression on the HF disease trajectory and resultant clinical outcomes.

Microbiota produced indole metabolites disrupt host cell mitochondrial energy production and inhibit Cryptosporidium parvum growth.

Cryptosporidiosis is a leading cause of life-threatening diarrhea in young children in resource-poor settings. Susceptibility rapidly declines with age, associated with changes in the microbiota. To explore microbial influences on susceptibility, we screened 85 microbiota- associated metabolites enriched in the adult gut for their effects on C. parvum growth in vitro. We identified eight inhibitory metabolites in three main classes: secondary bile salts/acids, a vitamin B 6 precursor, and indoles. Growth restriction of C. parvum by indoles did not depend on the host aryl hydrocarbon receptor (AhR) pathway. Instead, treatment impaired host mitochondrial function and reduced total cellular ATP, as well as directly reduced the membrane potential in the parasite mitosome, a degenerate mitochondria. Oral administration of indoles, or reconstitution of the gut microbiota with indole producing bacteria, delayed life cycle progression of the parasite in vitro and reduced severity of C. parvum infection in mice. Collectively, these findings indicate that microbiota metabolites contribute to colonization resistance to Cryptosporidium infection.

Microbiota-produced indole metabolites disrupt mitochondrial function and inhibit Cryptosporidium parvum growth.

Cryptosporidiosis is a leading cause of life-threatening diarrhea in young children in resource-poor settings. To explore microbial influences on susceptibility, we screened 85 microbiota-associated metabolites for their effects on Cryptosporidium parvum growth in vitro. We identify eight inhibitory metabolites in three main classes: secondary bile salts/acids, a vitamin B6 precursor, and indoles. Growth restriction of C. parvum by indoles does not depend on the host aryl hydrocarbon receptor (AhR) pathway. Instead, treatment impairs host mitochondrial function and reduces total cellular ATP, as well as directly reducing the membrane potential in the parasite mitosome, a degenerate mitochondria. Oral administration of indoles, or reconstitution of the gut microbiota with indole-producing bacteria, delays life cycle progression of the parasite in vitro and reduces the severity of C. parvum infection in mice. Collectively, these findings indicate that microbiota metabolites impair mitochondrial function and contribute to colonization resistance to Cryptosporidium infection.

Unexpected case of chagas disease reactivation in endomyocardial biopsy for evaluation of cardiac allograft rejection.

Acute Chagas disease reactivation (CDR) after cardiac transplantation is a well-known phenomenon in endemic countries of Central and South America and Mexico, but is rare outside of those countries. In this report, we describe a case of a 49-year-old male who presented 25 weeks after heart transplant with clinical features concerning for acute rejection, including malaise, anorexia, weight loss, and fever. His immunosuppression therapy included tacrolimus, mycophenolate, and prednisone. An endomyocardial biopsy revealed lymphocytic and eosinophilic inflammation, myocyte damage, and rare foci of intracellular organisms consistent with Trypanosoma cruzi amastigotes. The patient had no known history of Chagas disease. Upon additional questioning, the patient endorsed bites from reduviid bugs during childhood in El Salvador. Follow-up serum PCR testing was positive for T. cruzi DNA. Tests for other infectious organisms and donor specific antibodies were negative. This case illustrates the striking clinical and histologic similarities between acute cellular rejection and acute CDR with cardiac involvement in heart transplant patients, and thus emphasizes the importance of pre-transplant testing for Chagas in patients with epidemiologic risk factors.

Commensal Cryptosporidium colonization elicits a cDC1-dependent Th1 response that promotes intestinal homeostasis and limits other infections.

Cryptosporidium can cause severe diarrhea and morbidity, but many infections are asymptomatic. Here, we studied the immune response to a commensal strain of Cryptosporidium tyzzeri (Ct-STL) serendipitously discovered when conventional type 1 dendritic cell (cDC1)-deficient mice developed cryptosporidiosis. Ct-STL was vertically transmitted without negative health effects in wild-type mice. Yet, Ct-STL provoked profound changes in the intestinal immune system, including induction of an IFN-γ-producing Th1 response. TCR sequencing coupled with in vitro and in vivo analysis of common Th1 TCRs revealed that Ct-STL elicited a dominant antigen-specific Th1 response. In contrast, deficiency in cDC1s skewed the Ct-STL CD4 T cell response toward Th17 and regulatory T cells. Although Ct-STL predominantly colonized the small intestine, colon Th1 responses were enhanced and associated with protection against Citrobacter rodentium infection and exacerbation of dextran sodium sulfate and anti-IL10R-triggered colitis. Thus, Ct-STL represents a commensal pathobiont that elicits Th1-mediated intestinal homeostasis that may reflect asymptomatic human Cryptosporidium infection.

Heart Failure: Advanced Refractory Heart Failure.

End-stage heart failure (HF) is associated with an extremely poor prognosis. Progressive and/or persistent HF signs and symptoms in the setting of optimal therapy is the hallmark of more advanced disease. Physicians must be able to recognize patients with features of refractory HF to aid in timely evaluation for advanced therapy options. Left ventricular assist device implantation and heart transplantation prolong survival in patients with end-stage HF, but are options only for select patients. Timely referral for evaluation is necessary to prevent secondary irreversible end-organ dysfunction and to ascertain whether there are factors that can be addressed and corrected. All patients with end-stage HF should be offered referral for palliative care to aid in symptom management and improve quality of life. In addition, for patients who are not candidates for advanced therapy options, hospice should be discussed. In some cases, palliative home inotrope infusion can be considered for symptom management.

Neonatal Mouse Gut Metabolites Influence Cryptosporidium parvum Infection in Intestinal Epithelial Cells.

The protozoan parasite Cryptosporidium sp. is a leading cause of diarrheal disease in those with compromised or underdeveloped immune systems, particularly infants and toddlers in resource-poor localities. As an enteric pathogen, Cryptosporidium sp. invades the apical surface of intestinal epithelial cells, where it resides in close proximity to metabolites in the intestinal lumen. However, the effect of gut metabolites on susceptibility to Cryptosporidium infection remains largely unstudied. Here, we first identified which gut metabolites are prevalent in neonatal mice when they are most susceptible to Cryptosporidium parvum infection and then tested the isolated effects of these metabolites on C. parvum invasion and growth in intestinal epithelial cells. Our findings demonstrate that medium or long-chain saturated fatty acids inhibit C. parvum growth, perhaps by negatively affecting the streamlined metabolism in C. parvum, which is unable to synthesize fatty acids. Conversely, long-chain unsaturated fatty acids enhanced C. parvum invasion, possibly by modulating membrane fluidity. Hence, gut metabolites, either from diet or produced by the microbiota, influence C. parvum growth in vitro and may also contribute to the early susceptibility to cryptosporidiosis seen in young animals.IMPORTANCECryptosporidium sp. occupies a unique intracellular niche that exposes the parasite to both host cell contents and the intestinal lumen, including metabolites from the diet and produced by the microbiota. Both dietary and microbial products change over the course of early development and could contribute to the changes seen in susceptibility to cryptosporidiosis in humans and mice. Consistent with this model, we show that the immature gut metabolome influenced the growth of Cryptosporidium parvumin vitro Interestingly, metabolites that significantly altered parasite growth were fatty acids, a class of molecules that Cryptosporidium sp. is unable to synthesize de novo The enhancing effects of polyunsaturated fatty acids and the inhibitory effects of saturated fatty acids presented in this study may provide a framework for future studies into this enteric parasite's interactions with exogenous fatty acids during the initial stages of infection.

Defining Stage-Specific Activity of Potent New Inhibitors of Cryptosporidium parvum Growth In Vitro.

Cryptosporidium parvum and Cryptosporidium hominis have emerged as major enteric pathogens of infants in the developing world, in addition to their known importance in immunocompromised adults. Although there has been recent progress in identifying new small molecules that inhibit Cryptosporidium sp. growth in vitro or in animal models, we lack information about their mechanism of action, potency across the life cycle, and cidal versus static activities. Here, we explored four potent classes of compounds that include inhibitors that likely target phosphatidylinositol 4 kinase (PI4K), phenylalanine-tRNA synthetase (PheRS), and several potent inhibitors with unknown mechanisms of action. We utilized monoclonal antibodies and gene expression probes for staging life cycle development to define the timing of when inhibitors were active during the life cycle of Cryptosporidium parvum grown in vitro These different classes of inhibitors targeted different stages of the life cycle, including compounds that blocked replication (PheRS inhibitors), prevented the segmentation of daughter cells and thus blocked egress (PI4K inhibitors), or affected sexual-stage development (a piperazine compound of unknown mechanism). Long-term cultivation of C. parvum in epithelial cell monolayers derived from intestinal stem cells was used to distinguish between cidal and static activities based on the ability of parasites to recover from treatment. Collectively, these approaches should aid in identifying mechanisms of action and for designing in vivo efficacy studies based on time-dependent concentrations needed to achieve cidal activity.IMPORTANCE Currently, nitazoxanide is the only FDA-approved treatment for cryptosporidiosis; unfortunately, it is ineffective in immunocompromised patients, has varied efficacy in immunocompetent individuals, and is not approved in infants under 1 year of age. Identifying new inhibitors for the treatment of cryptosporidiosis requires standardized and quantifiable in vitro assays for assessing potency, selectivity, timing of activity, and reversibility. Here, we provide new protocols for defining which stages of the life cycle are susceptible to four highly active compound classes that likely inhibit different targets in the parasite. We also utilize a newly developed long-term culture system to define assays for monitoring reversibility as a means of defining cidal activity as a function of concentration and time of treatment. These assays should provide valuable in vitro parameters to establish conditions for efficacious in vivo treatment.

Five-year Outcomes of Pulmonary Hypertension With and Without Elevated Left Atrial Pressure in Patients Evaluated for Kidney Transplantation.

BACKGROUND: Pulmonary hypertension (PH) is frequently reported in patients with advanced chronic kidney disease and is associated with early allograft failure and death. However, the causes of PH are heterogeneous, and patient prognosis may vary by etiologic subtype. METHODS: Data from the University of North Carolina Cardiorenal Registry were examined to determine associations between PH, with or without elevated left atrial pressure (eLAP), and mortality in candidates for kidney transplantation. PH and eLAP were determined by Doppler echocardiography and by tissue Doppler imaging, respectively. RESULTS: From 2006 to 2013, 778 registry patients were screened preoperatively by echocardiography. Most patients were black (64%) and men (56%); the mean age was 56 years. PH was identified in 97 (12%) patients; of these, eLAP was prevalent in half. During a median follow-up of 4.4 years, 179 (23%) received a kidney transplant, and 195 (25%) died. After adjustments for demographics, comorbidities, dialysis vintage, and kidney transplantation, PH was associated with twice the 5-year mortality (hazard ratio [HR] = 2.11; 95% confidence interval [CI]: 1.48-3.03), with stronger associations in the absence of eLAP (HR = 2.87; 95% CI: 1.83-4.49) than with eLAP (HR = 1.11; 95% CI: 0.57-2.17), P for interaction = 0.01. CONCLUSIONS: The mortality risk associated with PH among patients with advanced chronic kidney disease appears to differ by etiology. Patients with PH in the absence of eLAP are at high risk of death and in need of focused attention. Future research efforts should investigate potential strategies to improve outcomes for these patients.

Pharmacological interventions for prevention and treatment of upper gastrointestinal bleeding in newborn infants.

BACKGROUND: Upper gastrointestinal bleeding is typically a mild, self-limiting condition that can affect both preterm and term neonates, although it can be severe particularly when associated with co-morbidities. Pharmacological interventions with a proton pump inhibitor (PPI), H2 receptor antagonist (H2RA), antacid, bismuth and sucralfate may have effects on both the prevention and treatment of upper gastrointestinal bleeding in infants. OBJECTIVES: To assess how different pharmacological interventions (PPIs, H2RAs, antacids, sucralfate or bismuth salts) administered to preterm and term neonates for the prevention or treatment of upper gastrointestinal bleeding to reduce morbidity and mortality compare with placebo or no treatment, supportive care, or each other. SEARCH METHODS: We used the standard search strategy of Cochrane Neonatal to search the Cochrane Central Register of Controlled Trials (CENTRAL 2018, Issue 6), MEDLINE via PubMed (1966 to 12 July 2018), Embase (1980 to 12 July 2018), and CINAHL (1982 to 12 July 2018). We also searched clinical trial databases, conference proceedings, the reference lists of retrieved articles for randomised controlled trials and quasi-randomised trials, and online for Chinese literature articles. SELECTION CRITERIA: We selected randomised, quasi-randomised and cluster-randomised trials involving preterm and term neonates. Trials were included if they used a proton pump inhibitor, H2 receptor antagonist, antacid, sucralfate or bismuth either for the prevention or treatment of upper gastrointestinal bleeding. DATA COLLECTION AND ANALYSIS: Two review authors independently assessed the eligibility of studies for inclusion, extracted data and assessed methodological quality. We conducted meta-analysis using a fixed-effect model. We used the GRADE approach to assess quality of evidence. MAIN RESULTS: Eleven studies with 818 infants met the criteria for inclusion in this review.Four trials with 329 infants assessed the use of an H2 receptor antagonist for prevention of upper gastrointestinal bleeding in high-risk newborn infants. Meta-analysis of these four trials identified a reduction in any upper gastrointestinal bleeding when using an H2 receptor antagonist (typical risk ratio (RR) 0.36, 95% confidence interval (CI) 0.22 to 0.58; typical risk difference (RD) -0.20, 95% CI -0.28 to -0.11; number needed to treat for an additional beneficial outcome (NNTB) 5, 95% CI 4 to 9). The quality of evidence was moderate. A single trial with 53 infants assessing prevention of upper gastrointestinal bleeding reported no difference in mortality in infants assigned H2 receptor antagonist versus no treatment; however the quality of evidence was very low.Seven trials with 489 infants assessed an inhibitor of gastric acid (H2 receptor antagonist or proton pump inhibitor) for treatment of gastrointestinal bleeding in newborn infants. Meta-analysis of two trials (131 infants) showed no difference in mortality from use of a H2 receptor antagonist compared to no treatment. The quality of evidence was low. Meta-analysis of two trials (104 infants) showed a reduction in duration of upper gastrointestinal bleeding from use of an inhibitor of gastric acid compared to no treatment (mean difference -1.06 days, 95% CI -1.28 to -0.84). The quality of evidence was very low. Meta-analysis of six trials (451 infants) showed a reduction in continued upper gastrointestinal bleeding from use of any inhibitor of gastric acid compared to no treatment (typical RR 0.36, 95% CI 0.26 to 0.49; typical RD -0.26, 95% CI -0.33, -0.19; NNTB 4, 95% CI 3 to 5). The quality of evidence was low. There were no significant subgroup differences in duration of upper gastrointestinal bleeding or of continued upper gastrointestinal bleeding according to type of inhibitor of gastric acid. A single trial (38 infants) reported no difference in anaemia requiring blood transfusion from use of a H2 receptor antagonist compared to no treatment.Although no serious adverse events were reported from the use of a H2 receptor antagonist or proton pump inhibitor, some neonatal morbidities - including necrotising enterocolitis, ventilator-associated pneumonia, duration of ventilation and respiratory support, and duration of hospital stay - were not reported. Long-term outcome was not reported. AUTHORS' CONCLUSIONS: There is moderate-quality evidence that use of an H2 receptor antagonist reduces the risk of gastrointestinal bleeding in newborn infants at high risk of gastrointestinal bleeding. There is low-quality evidence that use of an inhibitor of gastric acid (H2 receptor antagonist or proton pump inhibitor) reduces the duration of upper gastrointestinal bleeding and the incidence of continued gastric bleeding in newborn infants with gastrointestinal bleeding. However, there is no evidence that use of an inhibitor of gastric acid in newborn infants affects mortality or the need for blood transfusion. As no study reported the incidence of necrotising enterocolitis, ventilator- or hospital-associated pneumonia, sepsis, or long-term outcome, the safety of inhibitors of gastric acid secretion is unclear.

A Stem-Cell-Derived Platform Enables Complete Cryptosporidium Development In Vitro and Genetic Tractability.

Despite being a frequent cause of severe diarrheal disease in infants and an opportunistic infection in immunocompromised patients, Cryptosporidium research has lagged due to a lack of facile experimental methods. Here, we describe a platform for complete life cycle development and long-term growth of C. parvum in vitro using "air-liquid interface" (ALI) cultures derived from intestinal epithelial stem cells. Transcriptomic profiling revealed that differentiating epithelial cells grown under ALI conditions undergo profound changes in metabolism and development that enable completion of the parasite life cycle in vitro. ALI cultures support parasite expansion > 100-fold and generate viable oocysts that are transmissible in vitro and to mice, causing infection and animal death. Transgenic parasite lines created using CRISPR/Cas9 were used to complete a genetic cross in vitro, demonstrating Mendelian segregation of chromosomes during meiosis. ALI culture provides an accessible model that will enable innovative studies into Cryptosporidium biology and host interactions.

Infant formulas containing hydrolysed protein for prevention of allergic disease.

BACKGROUND: Infant formulas containing hydrolysed proteins have been widely advocated for preventing allergic disease in infants, in place of standard cow's milk formula (CMF). However, it is unclear whether the clinical trial evidence supports this. OBJECTIVES: To compare effects on allergic disease when infants are fed a hydrolysed formula versus CMF or human breast milk. If hydrolysed formulas are effective, to determine what type of hydrolysed formula is most effective, including extensively or partially hydrolysed formula (EHF/PHF). To determine whether infants at low or high risk of allergic disease, and whether infants receiving early short-term (first few days after birth) or prolonged formula feeding benefit from hydrolysed formulas. SEARCH METHODS: We searched the Cochrane Central Register of Controlled Trials (CENTRAL 2017, Issue 11), MEDLINE (1948 to 3 November 2017), and Embase (1974 to 3 November 2017). We also searched clinical trials databases, conference proceedings, and the reference lists of retrieved articles and previous reviews for randomised controlled trials and quasi-randomised trials. SELECTION CRITERIA: We searched for randomised and quasi-randomised trials that compared use of a hydrolysed formula versus human milk or CMF. Outcomes with ≥ 80% follow-up of participants from eligible trials were eligible for inclusion. DATA COLLECTION AND ANALYSIS: Two review authors independently selected trials, assessed trial quality and extracted data from the included studies. Fixed-effect analyses were performed. The treatment effects were expressed as risk ratio (RR) and risk difference (RD) with 95% confidence intervals and quality of evidence using the GRADE quality of evidence approach. The primary outcome was all allergic disease (including asthma, atopic dermatitis, allergic rhinitis and food allergy). MAIN RESULTS: A total of 16 studies were included.Two studies assessed the effect of three to four days infant supplementation with an EHF while in hospital after birth versus pasteurised human milk feed. A single study enrolling 90 infants reported no difference in all allergic disease (RR 1.43, 95% CI 0.38 to 5.37) or any specific allergic disease up to childhood including cow's milk allergy (CMA) (RR 7.11, 95% CI 0.35 to 143.84). A single study reported no difference in infant CMA (RR 0.87, 95% CI 0.52 to 1.46; participants = 3559). Quality of evidence was assessed as very low for all outcomes.No eligible trials compared prolonged hydrolysed formula versus human milk feeding.Two studies assessed the effect of three to four days infant supplementation with an EHF versus a CMF. A single study enrolling 90 infants reported no difference in all allergic disease (RR 1.37, 95% CI 0.33 to 5.71; participants = 77) or any specific allergic disease including CMA up to childhood. A single study reported a reduction in infant CMA of borderline significance (RR 0.62, 95% CI 0.38 to 1.00; participants = 3473). Quality of evidence was assessed as very low for all outcomes.Twelve studies assessed the effect of prolonged infant feeding with a hydrolysed formula compared with a CMF. The data showed no difference in all allergic disease in infants (typical RR 0.88, 95% CI 0.76 to 1.01; participants = 2852; studies = 8) and children (typical RR 0.85, 95% CI 0.69 to 1.05; participants = 950; studies = 2), and no difference in any specific allergic disease including infant asthma (typical RR 0.57, 95% CI 0.31 to 1.04; participants = 318; studies = 4), eczema (typical RR 0.93, 95% CI 0.79 to 1.09; participants = 2896; studies = 9), rhinitis (typical RR 0.52, 95% CI 0.14 to 1.85; participants = 256; studies = 3), food allergy (typical RR 1.42, 95% CI 0.87 to 2.33; participants = 479; studies = 2), and CMA (RR 2.31, 95% CI 0.24 to 21.97; participants = 338; studies = 1). Quality of evidence was assessed as very low for all outcomes. AUTHORS' CONCLUSIONS: We found no evidence to support short-term or prolonged feeding with a hydrolysed formula compared with exclusive breast feeding for prevention of allergic disease. Very low-quality evidence indicates that short-term use of an EHF compared with a CMF may prevent infant CMA. Further trials are recommended before implementation of this practice.We found no evidence to support prolonged feeding with a hydrolysed formula compared with a CMF for prevention of allergic disease in infants unable to be exclusively breast fed.

The Value of Bedside Echocardiogram in the Setting of Acute and Chronic Pulmonary Embolism.

Echocardiography is valuable in the evaluation and risk stratification of patients with acute and chronic pulmonary embolism (PE). Patients with acute PE who have echocardiographic evidence of right ventricular dilatation and/or right ventricular dysfunction have a worse prognosis. A minority of patients with acute PE can develop chronic thromboembolic pulmonary hypertension. Patients with chronic thromboembolic pulmonary hypertension often have echocardiographic evidence of elevated pulmonary arterial pressures, right ventricular hypertrophy, right ventricular dysfunction, and/or left ventricular impaired relaxation.

The Maternal Effect Gene Wds Controls Wolbachia Titer in Nasonia.

Maternal transmission of intracellular microbes is pivotal in establishing long-term, intimate symbioses. For germline microbes that exert negative reproductive effects on their hosts, selection can theoretically favor the spread of host genes that counteract the microbe's harmful effects. Here, we leverage a major difference in bacterial (Wolbachia pipientis) titers between closely related wasp species with forward genetic, transcriptomic, and cytological approaches to map two quantitative trait loci that suppress bacterial titers via a maternal effect. Fine mapping and knockdown experiments identify the gene Wolbachia density suppressor (Wds), which dominantly suppresses bacterial transmission from mother to embryo. Wds evolved by lineage-specific non-synonymous changes driven by positive selection. Collectively, our findings demonstrate that a genetically simple change arose by positive Darwinian selection in less than a million years to regulate maternally transmitted bacteria via a dominant, maternal effect gene.

Lower versus higher oxygen concentrations titrated to target oxygen saturations during resuscitation of preterm infants at birth.

BACKGROUND: Initial resuscitation with air is well tolerated by most infants born at term. However, the optimal fractional inspired oxygen concentration (FiO2 - proportion of the breathed air that is oxygen) targeted to oxygen saturation (SpO2 - an estimate of the amount of oxygen in the blood) for infants born preterm is unclear. OBJECTIVES: To determine whether lower or higher initial oxygen concentrations, when titrated according to oxygen saturation targets during the resuscitation of preterm infants at birth, lead to improved short- and long-term mortality and morbidity. SEARCH METHODS: We conducted electronic searches of the Cochrane Central Register of Controlled Trials (13 October 2017), Ovid MEDLINE (1946 to 13 October 2017), Embase (1974 to 13 October 2017) and CINAHL (1982 to 13 October 2017); we also searched previous reviews (including cross-references), contacted expert informants, and handsearched journals. SELECTION CRITERIA: We included randomised controlled trials (including cluster- and quasi-randomised trials) which enrolled preterm infants requiring resuscitation following birth and allocated them to receive either lower (FiO2 < 0.4) or higher (FiO2 ≥ 0.4) initial oxygen concentrations titrated to target oxygen saturation. DATA COLLECTION AND ANALYSIS: Two review authors independently assessed the eligibility of studies for inclusion, extracted data and assessed methodological quality. Primary outcomes included mortality near term or at discharge (latest reported) and neurodevelopmental disability. We conducted meta-analysis using a fixed-effect model. We assessed the quality of the evidence using GRADE. MAIN RESULTS: The search identified 10 eligible trials. Meta-analysis of the 10 included studies (914 infants) showed no difference in mortality to discharge between lower (FiO2 < 0.4) and higher (FiO2 ≥ 0.4) initial oxygen concentrations targeted to oxygen saturation (risk ratio (RR) 1.05, 95% confidence interval (CI) 0.68 to 1.63). We identified no heterogeneity in this analysis. We graded the quality of the evidence as low due to risk of bias and imprecision. There were no significant subgroup effects according to inspired oxygen concentration strata (FiO2 0.21 versus ≥ 0.4 to < 0.6; FiO2 0.21 versus ≥ 0.6 to 1.0; and FiO2 ≥ 0.3 to < 0.4 versus ≥ 0.6 to 1.0). Subgroup analysis identified a single trial that reported increased mortality from use of lower (FiO2 0.21) versus higher (FiO2 1.0) initial oxygen concentration targeted to a lowest SpO2 of less than 85%, whereas meta-analysis of nine trials targeting a lowest SpO2 of 85% to 90% found no difference in mortality.Meta-analysis of two trials (208 infants) showed no difference in neurodevelopmental disability at 24 months between infants receiving lower (FiO2 < 0.4) versus higher (FiO2 > 0.4) initial oxygen concentrations targeted to oxygen saturation. Other outcomes were incompletely reported by studies. Overall, we found no difference in use of intermittent positive pressure ventilation or intubation in the delivery room; retinopathy (damage to the retina of the eyes, measured as any retinopathy and severe retinopathy); intraventricular haemorrhage (any and severe); periventricular leukomalacia (a type of white-matter brain injury); necrotising enterocolitis (a condition where a portion of the bowel dies); chronic lung disease at 36 weeks' gestation; mortality to follow up; postnatal growth failure; and patent ductus arteriosus. We graded the quality of the evidence for these outcomes as low or very low. AUTHORS' CONCLUSIONS: There is uncertainty as to whether initiating post birth resuscitation in preterm infants using lower (FiO2 < 0.4) or higher (FiO2 ≥ 0.4) oxygen concentrations, targeted to oxygen saturations in the first 10 minutes, has an important effect on mortality or major morbidity, intubation during post birth resuscitation, other resuscitation outcomes, and long-term outcomes including neurodevelopmental disability. We assessed the quality of the evidence for all outcomes as low to very low. Further large, well designed trials are needed to assess the effect of using different initial oxygen concentrations and the effect of targeting different oxygen saturations.