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Drosophila sechellia is a dietary specialist fruit fly that evolved from a generalist ancestor to specialize on the toxic fruit of Morinda citrifolia. This species pair has been the subject of numerous studies where the goal has largely been to determine the genetic basis of adaptations associated with host specialization. Because one of the most striking features of M. citrifolia fruit is the production of toxic volatile compounds that kill insects, most genomic studies in D. sechellia to date have focused on gene expression responses to the toxic compounds in its food. In this study, we aim to identify new genes important for host specialization by profiling gene expression response to 3,4-dihydroxyphenylalanine (L-DOPA). Recent work found it to be highly abundant in M. citrifolia, critical for reproductive success of D. sechellia, and supplementation of diet with the downstream pathway product dopamine can influence toxin resistance phenotypes in related species. Here we used a combination of functional genetics and genomics techniques to identify new genes that are important for D. sechellia ecological adaptation to this new niche. We show that L-DOPA exposure can affect toxin resistance phenotypes, identify genes with plastic responses to L-DOPA exposure, and functionally test an identified candidate gene. We found that knock-down of Esterase 6 (Est6) in a heterologous species alters toxin resistance suggesting Est6 may play an important role in D. sechellia host specialization.

The dietary specialist fruit fly Drosophila sechellia has evolved to specialize on the toxic fruit of its host plant Morinda citrifolia. Toxicity of Morinda fruit is primarily due to high levels of octanoic acid (OA). Using RNA interference (RNAi), prior work found that knockdown of Osiris family genes Osiris 6 (Osi6), Osi7, and Osi8 led to increased susceptibility to OA in adult D. melanogaster flies, likely representing genes underlying a Quantitative Trait Locus (QTL) for OA resistance in D. sechellia. While genes in this major effect locus are beginning to be revealed, prior work has shown at least five regions of the genome contribute to OA resistance. Here, we identify new candidate OA resistance genes by performing differential gene expression analysis using RNA-sequencing (RNA-seq) on control and OA-exposed D. sechellia flies. We found 104 significantly differentially expressed genes with annotated orthologs in D. melanogaster, including six Osiris gene family members, consistent with previous functional studies and gene expression analyses. Gene ontology (GO) term enrichment showed significant enrichment for cuticle development in upregulated genes and significant enrichment of immune and defense responses in downregulated genes, suggesting important aspects of the physiology of D. sechellia that may play a role in OA resistance. In addition, we identified five candidate OA resistance genes that potentially underlie QTL peaks outside of the major effect region, representing promising new candidate genes for future functional studies.

The underlying genetic basis of adaptive phenotypic changes is generally poorly understood, yet a growing number of case studies are beginning to shed light on important questions about the molecular nature and pleiotropy of such changes. We use Drosophila sechellia, a dietary specialist fruit fly that evolved to specialize on a single toxic host plant, Morinda citrifolia, as a model for adaptive phenotypic change and seek to determine the genetic basis of traits associated with host specialization in this species. The fruit of M. citrifolia is toxic to other drosophilids, primarily due to high levels of the defense chemical octanoic acid (OA), yet D. sechellia has evolved resistance to OA. Our prior work identified three Osiris family genes that reside in a fine‐mapped QTL for OA resistance: Osiris 6 (Osi6), Osi7, and Osi8, which can alter OA resistance in adult D. melanogaster when knocked down with RNA interference suggesting they may contribute to OA resistance in D. sechellia. Genetic mapping identified overlapping genomic regions involved in larval and adult OA resistance in D. sechellia, yet it remains unknown whether Osiris genes contribute to resistance in both life stages. Furthermore, because multiple genomic regions contribute to OA resistance, we aim to identify other gene(s) involved in this adaptation. Here, we identify candidate larval OA resistance genes using RNA sequencing to measure genome‐wide differential gene expression in D. sechellia larvae after exposure to OA and functionally test identified genes for a role in OA resistance. We then test the Osiris genes previously shown to alter adult OA resistance for effects on OA resistance in larvae. We found that Osi8 knockdown decreased OA resistance in D. melanogaster larvae. These data suggest that evolved changes in Osi8 could impact OA resistance in multiple life stages while Osi6 and Osi7 may only impact adult resistance to OA. Drosophila sechellia is an island endemic host specialist fruit fly that feeds exclusively on the toxic fruit of the Morinda citrifolia plant. Evolved resistance to the primary toxin, octanoic acid, has been studied in depth in adult individuals, but whether the same genes or different genes underlie resistance in the larval life stage is unknown. Here, we found that one adult resistance gene may be important for larval toxin resistance but other adult resistance genes may not be involved and identified new candidates for future genetic studies.

Microglia are brain resident macrophages, which have specialized functions important in brain development and in disease. They colonize the brain in early embryonic stages, but few factors that drive the migration of yolk sac macrophages (YSMs) into the embryonic brain , or regulate their acquisition of specialized properties are currently known. Here, we present a CRISPR/Cas9-based in vivo reverse genetic screening pipeline to identify new microglia regulators using zebrafish. Zebrafish larvae are particularly suitable due to their external development, transparency and conserved microglia features. We targeted putative microglia regulators, by Cas9/gRNA-complex injections, followed by neutral red-based visualization of microglia. Microglia were quantified automatically in 3-day-old larvae using a software tool we called SpotNGlia. We identified that loss of the zebrafish colony stimulating factor 1 receptor (CSF1R) ligand IL34, caused reduced microglia numbers. Previous studies on the role of the IL34 on microglia development in vivo were ambiguous. Our data, and a concurrent paper, show that in zebrafish, il34 is required during the earliest seeding of the brain by microglia. Our data also indicate that Il34 is required for YSM distribution to other organs. Disruption of the other CSF1R ligand, Csf1, did not reduce microglia numbers in mutants, whereas overexpression increased the number of microglia. This shows Csf1 can influence microglia numbers, but might not be essential for the early seeding of the brain. In all, we identified il34 as a modifier of microglia colonization, by affecting distribution of YSMs to target organs, validating our reverse genetic screening pipeline in zebrafish.

ObjectiveTo describe primary health care (consultation characteristics and management) for patients contacting their general practitioner (GP) with a respiratory tract infection (RTI) early on in the COVID-19 pandemic in contrasting European countries, with comparison to prepandemic findings.SettingPrimary care in 16 countries (79 practices), when no routine SARS-CoV-2 testing was generally available.Design and participantsBefore (n=4376) and early in the pandemic (n=3301), patients with RTI symptoms were registered in this prospective audit study.Outcome measuresConsultation characteristics (type of contact and use of PPE) and management characteristics (clinical assessments, diagnostic testing, prescribing, advice and referral) were registered. Differences in these characteristics between countries and between pandemic and prepandemic care are described.ResultsCare for patients with RTIs rapidly switched to telephone/video consultations (10% in Armenia, 91% in Denmark), and when consultations were face-to-face, GPs used PPE during 97% (95% CI 96% to 98%) of contacts. Laboratory testing for SARS-CoV-2 in primary care patients with RTIs was rapidly implemented in Denmark (59%) and Germany (31%), while overall testing for C reactive protein decreased. The proportion of patients prescribed antibiotics varied considerably between countries (3% in Belgium, 48% in UK) and was lower during the pandemic compared with the months before, except for Greece, Poland and UK. GPs provided frequent and varied COVID-related advice and more frequently scheduled a follow-up contact (50%, 95% CI 48% to 52%). GPs reported a slightly higher degree of confidence in the likely effectiveness of their management in face-to-face (73% (very) confident, 95% CI 71% to 76%) than in virtual consultations (69%, 95% CI 67% to 71%).ConclusionsDespite between-country variation in consultation characteristics, access to SARS-CoV-2 laboratory testing and medication prescribing, GPs reported a high degree of confidence in managing their patients with RTIs in the emerging pandemic. Insight in the highly variable pandemic responses, as measured in this multicountry audit, can aid in fine-tuning national action and in coordinating a pan-European response during future pandemic threats.

Up to 80% of antibiotics are prescribed in the community. An assessment of prescribing by indication will help to identify areas where improvement can be made. A point prevalence audit study (PPAS) of consecutive respiratory tract infection (RTI) consultations in general practices in 13 European countries was conducted in January–February 2020 (PPAS-1) and again in 2022 (PPAS-4). The European Surveillance of Antibiotic Consumption quality indicators (ESAC-QI) were calculated to identify where improvements can be made. A total of 3618 consultations were recorded for PPAS-1 and 2655 in PPAS-4. Bacterial aetiology was suspected in 26% (PPAS-1) and 12% (PPAS-4), and an antibiotic was prescribed in 30% (PPAS-1) and 16% (PPAS-4) of consultations. The percentage of adult patients with bronchitis who receive an antibiotic should, according to the ESAC-QI, not exceed 30%, which was not met by participating practices in any country except Denmark and Spain. For patients (≥1) with acute upper RTI, less than 20% should be prescribed an antibiotic, which was achieved by general practices in most countries, except Ireland (both PPAS), Croatia (PPAS-1), and Greece (PPAS-4) where prescribing for acute or chronic sinusitis (0–20%) was also exceeded. For pneumonia in adults, prescribing is acceptable for 90–100%, and this is lower in most countries. Prescribing for tonsillitis (≥1) exceeded the ESAC-QI (0–20%) in all countries and was 69% (PPAS-1) and 75% (PPAS-4). In conclusion, ESAC-QI applied to PPAS outcomes allows us to evaluate appropriate antibiotic prescribing by indication and benchmark general practices and countries.

Abstract Background Antimicrobial stewardship (AMS) and infection prevention and control (IPC) programs are crucial for reducing antimicrobial resistance in hospitals. Existing quality indicators (QIs) for these programs are mainly qualitative, hindering external benchmarking. PILGRIM (NCT03765528) is a prospective multinational cohort study evaluating the impact of antibiotic prescription quality on intestinal domination by healthcare-associated pathogens. Objective In this sub-study, we develop a quantitative scoring tool for AMS and IPC programs to facilitate standardized assessments of programs and support clinical studies. Methods We used a RAND-modified Delphi consensus procedure to establish a scoring system for AMS and IPC programs. The tool was tested using data collected from eight hospitals in five countries during 2019–2024. We evaluated temporal associations between scores, Clostridioides difficile cases, hand disinfectant and antibiotic use. Results We assessed 98 QIs, resulting in in a final set of 62 QIs (35 for AMS and 27 for IPC). For our sites, the overall median score was 29 out of 50 (IQR 28–31) for AMS and 36 out of 50 (IQR 33–38) for IPC programs. Higher-scoring sites decrease antibiotic use over time. IPC scores were positively correlated with hand disinfectant use. Conclusion This quantitative scoring scheme represents a promising step towards standardizing assessments of AMS and IPC programs in high-income settings, enabling external comparisons and supporting future clinical studies. Further validation is needed to refine its predictive validity and ensure its utility in diverse healthcare settings.

Microglia are brain resident macrophages, which have specialized functions important in brain development and in disease. They colonize the brain in early embryonic stages, but few factors that drive the migration of yolk sac macrophages into the embryonic brain, or regulate their acquisition of specialized properties are currently known. Here, we present a CRISPR/Cas9-based in vivo reverse genetic screening pipeline to identify new regulators important for microglia development using zebrafish. Zebrafish larvae are particularly suitable due to their external development, transparency, high fecundity and conserved microglia features. We targeted putative microglia regulators, including signature genes and non-cell autonomous factors, by Cas9/gRNA-complex injections, followed by neutral red-based visualization of microglia. Microglia were quantified automatically in 3-day-old larvae using a software tool we called SpotNGlia. We identified that loss of function of the zebrafish homolog of the colony stimulating factor 1 receptor (CSF1R) ligand IL34, caused strongly reduced microglia numbers in early development. Previous studies on the role of the IL34 on microglia development in vivo were ambiguous. Our data, and a concurrent paper, show that in zebrafish, il34 is required during the earliest seeding of the brain by microglia progenitors. Our data also indicate that Il34 is required for distribution to other organs. Previously, we showed that csf1ra and csf1rb double mutant zebrafish have no microglia. As there is a moderate effect of il34 on microglia development, relative to the effect csf1r, additional Csf1r-dependent signalling may be needed for establishment of the microglia network. In all, we identified il34 as a modifier of microglia colonization, by affecting distribution of yolk sac macrophages to target organs, validating our reverse genetic screening pipeline in zebrafish which can be used for the identification of additional regulators of microglia development.