HtrA, fatty acids, and membrane protein interplay in Chlamydia trachomatis to impact stress response and trigger early cellular exit.

Chlamydia trachomatis is an intracellular bacterial pathogen that undergoes a biphasic developmental cycle, consisting of intracellular reticulate bodies and extracellular infectious elementary bodies. A conserved bacterial protease, HtrA, was shown previously to be essential for Chlamydia during the reticulate body phase, using a novel inhibitor (JO146). In this study, isolates selected for the survival of JO146 treatment were found to have polymorphisms in the acyl-acyl carrier protein synthetase gene (aasC). AasC encodes the enzyme responsible for activating fatty acids from the host cell or synthesis to be incorporated into lipid bilayers. The isolates had distinct lipidomes with varied fatty acid compositions. A reduction in the lipid compositions that HtrA prefers to bind to was detected, yet HtrA and MOMP (a key outer membrane protein) were present at higher levels in the variants. Reduced progeny production and an earlier cellular exit were observed. Transcriptome analysis identified that multiple genes were downregulated in the variants especially stress and DNA processing factors. Here, we have shown that the fatty acid composition of chlamydial lipids, HtrA, and membrane proteins interplay and, when disrupted, impact chlamydial stress response that could trigger early cellular exit. IMPORTANCE: Chlamydia trachomatis is an important obligate intracellular pathogen that has a unique biphasic developmental cycle. HtrA is an essential stress or virulence protease in many bacteria, with many different functions. Previously, we demonstrated that HtrA is critical for Chlamydia using a novel inhibitor. In the present study, we characterized genetic variants of Chlamydia trachomatis with reduced susceptibility to the HtrA inhibitor. The variants were changed in membrane fatty acid composition, outer membrane proteins, and transcription of stress genes. Earlier and more synchronous cellular exit was observed. Combined, this links stress response to fatty acids, membrane proteins, and HtrA interplay with the outcome of disrupted timing of chlamydial cellular exit.

Enhancing sustainable crop cultivation: The impact of renewable soil amendments and digestate fertilizer on crop growth and nutrient composition.

Utilizing digestate as a fertilizer enhances soil nutrient content, improves fertility, and minimizes nutrient runoff, mitigating water pollution risks. This alternative approach replaces commercial fertilizers, thereby reducing their environmental impact and lowering greenhouse gas emissions associated with fertilizer production and landfilling. Herein, this study aimed to evaluate the impact of various soil amendments, including carbon fractions from waste materials (biochar, compost, and cocopeat), and food waste anaerobic digestate application methods on tomato plant growth (Solanum lycopersicum) and soil fertility. The results suggested that incorporating soil amendments (biochar, compost, and cocopeat) into the potting mix alongside digestate application significantly enhances crop yields, with increases ranging from 12.8 to 17.3% compared to treatments without digestate. Moreover, the combination of soil-biochar amendment and digestate application suggested notable improvements in nitrogen levels by 20.3% and phosphorus levels by 14%, surpassing the performance of the those without digestate. Microbial analysis revealed that the soil-biochar amendment significantly enhanced biological nitrification processes, leading to higher nitrogen levels compared to soil-compost and soil-cocopeat amendments, suggesting potential nitrogen availability enhancement within the rhizosphere's ecological system. Chlorophyll content analysis suggested a significant 6.91% increase with biochar and digestate inclusion in the soil, compared to the treatments without digestate. These findings underscore the substantial potential of crop cultivation using soil-biochar amendments in conjunction with organic fertilization through food waste anaerobic digestate, establishing a waste-to-food recycling system.

Phylogenetic relationship and virulence composition of Escherichia coli O26:H11 cattle and human strain collections in Scotland; 2002-2020.

O26 is the commonest non-O157 Shiga toxin (stx)-producing Escherichia coli serogroup reported in human infections worldwide. Ruminants, particularly cattle, are the primary reservoir source for human infection. In this study, we compared the whole genomes and virulence profiles of O26:H11 strains (n = 99) isolated from Scottish cattle with strains from human infections (n = 96) held by the Scottish Escherichia coli O157/STEC Reference Laboratory, isolated between 2002 and 2020. Bovine strains were from two national cross-sectional cattle surveys conducted between 2002-2004 and 2014-2015. A maximum likelihood phylogeny was constructed from a core-genome alignment with the O26:H11 strain 11368 reference genome. Genomes were screened against a panel of 2,710 virulence genes using the Virulence Finder Database. All stx-positive bovine O26:H11 strains belonged to the ST21 lineage and were grouped into three main clades. Bovine and human source strains were interspersed, and the stx subtype was relatively clade-specific. Highly pathogenic stx2a-only ST21 strains were identified in two herds sampled in the second cattle survey and in human clinical infections from 2010 onwards. The closest pairwise distance was 9 single-nucleotide polymorphisms (SNPs) between Scottish bovine and human strains and 69 SNPs between the two cattle surveys. Bovine O26:H11 was compared to public EnteroBase ST29 complex genomes and found to have the greatest commonality with O26:H11 strains from the rest of the UK, followed by France, Italy, and Belgium. Virulence profiles of stx-positive bovine and human strains were similar but more conserved for the stx2a subtype. O26:H11 stx-negative ST29 (n = 17) and ST396 strains (n = 5) were isolated from 19 cattle herds; all were eae-positive, and 10 of these herds yielded strains positive for ehxA, espK, and Z2098, gene markers suggestive of enterohaemorrhagic potential. There was a significant association (p < 0.001) between nucleotide sequence percent identity and stx status for the bacteriophage insertion site genes yecE for stx2 and yehV for stx1. Acquired antimicrobial resistance genes were identified in silico in 12.1% of bovine and 17.7% of human O26:H11 strains, with sul2, tet, aph(3″), and aph(6″) being most common. This study describes the diversity among Scottish bovine O26:H11 strains and investigates their relationship to human STEC infections.

An open-source digital contact tracing system tailored to haulage.

Digital contact tracing presents numerous advantages compared to manual contact tracing methods, especially in terms of enhanced speed and automation. Nevertheless, a lack of comprehensive evaluation regarding functionality, efficiency, benefits, and acceptance within communities remains. Here we primarily focus on the functionality of THEA-GS, an open-source digital contact tracing tool developed through consultation with stakeholders. Additionally, we provide insights from its implementation on a limited sample of haulage drivers in Uganda, serving as a representative case for a low- and middle-income country. THEA-GS comprises two primary components: (a) a smartphone application, and (b) a suite of server-programs responsible for data processing and analysis, including databases and a web-based interface featuring dashboards. In essence, the mobile application records the timestamped location of haulage drivers within the road network and identifies possible transmission hotspots by analyzing factors such as the duration of stops and the communities associated with them. The tool can be integrated with national infrastructure to compare drivers' diagnostic results and contact structure, thereby generating individual and community risk assessments relative to the road network. During the Omicron-variant wave of the COVID-19 pandemic, a total of 3,270 haulage drivers were enrolled between October 2021 and October 2022. Around 75% of these drivers utilized THEA-GS for approximately two months. Based on an analysis of 3,800 test results, which included 48 positive cases, 125 contacts, and 40 million time-stamped GPS points, THEA-GS shows a significant speed improvement, being approximately 90 times faster than MCT. For instance, the average time from sample collection to notifying a case and their contacts was approximately 70 and 80 min, respectively. The adoption of this tool encountered challenges, mainly due to drivers' awareness of its purpose and benefits for public health. THEA-GS is a place-based digital contact tracing tool specifically designed to assist National Public Health Institutions in managing infectious disease outbreaks involving the haulage industry as a high-risk group. While its utility, acceptance, and accuracy have not been fully evaluated, our preliminary tests conducted in Uganda indicate the tool's functionality is robust, but social acceptance and adoption are heavily reliant on establishing trust among users.

Distinctive hospital and community resistomes in Scottish urban wastewater: Metagenomics of a paired wastewater sampling design.

The wastewater microbiome contains a multitude of resistant bacteria of human origin, presenting an opportunity for surveillance of resistance in the general population. However, wastewater microbial communities are also influenced by clinical sources, such as hospitals. Identifying signatures of the community and hospital resistome in wastewater is needed for interpretation and risk analysis. In this study, we compare the resistome and microbiome of hospital, community, and mixed municipal wastewater to investigate how and why the composition of these different sites differ. We conducted shotgun metagenomic analysis on wastewater samples from eight wastewater treatment plants (WWTPs), four hospitals, and four community sites in Scotland, using a paired sampling design. Cluster analysis and source attribution random forest models demonstrated that the hospital resistome was distinct from community and WWTP resistomes. Hospital wastewater had a higher abundance and diversity of resistance genes, in keeping with evidence that hospitals act as a reservoir and enricher of resistance. However, this distinctive 'hospital' signature appeared to be weak in the resistome of downstream WWTPs, likely due to dilution. We conclude that hospital and community wastewater resistomes differ, with the hospital wastewater representing a reservoir of patient- and hospital environment-associated bacteria. However, this 'hospital' signature is transient and does not overwhelm the community signature in the resistome of the downstream WWTP influent.

Epidemiological connectivity between humans and animals across an urban landscape.

Urbanization is predicted to be a key driver of disease emergence through human exposure to novel, animal-borne pathogens. However, while we suspect that urban landscapes are primed to expose people to novel animal-borne diseases, evidence for the mechanisms by which this occurs is lacking. To address this, we studied how bacterial genes are shared between wild animals, livestock, and humans (n = 1,428) across Nairobi, Kenya-one of the world's most rapidly developing cities. Applying a multilayer network framework, we show that low biodiversity (of both natural habitat and vertebrate wildlife communities), coupled with livestock management practices and more densely populated urban environments, promotes sharing of Escherichia coli-borne bacterial mobile genetic elements between animals and humans. These results provide empirical support for hypotheses linking resource provision, the biological simplification of urban landscapes, and human and livestock demography to urban dynamics of cross-species pathogen transmission at a landscape scale. Urban areas where high densities of people and livestock live in close association with synanthropes (species such as rodents that are more competent reservoirs for zoonotic pathogens) should be prioritized for disease surveillance and control.

Rapid metagenomic sequencing for diagnosis and antimicrobial sensitivity prediction of canine bacterial infections.

Antimicrobial resistance is a major threat to human and animal health. There is an urgent need to ensure that antimicrobials are used appropriately to limit the emergence and impact of resistance. In the human and veterinary healthcare setting, traditional culture and antimicrobial sensitivity testing typically requires 48-72 h to identify appropriate antibiotics for treatment. In the meantime, broad-spectrum antimicrobials are often used, which may be ineffective or impact non-target commensal bacteria. Here, we present a rapid, culture-free, diagnostics pipeline, involving metagenomic nanopore sequencing directly from clinical urine and skin samples of dogs. We have planned this pipeline to be versatile and easily implementable in a clinical setting, with the potential for future adaptation to different sample types and animals. Using our approach, we can identify the bacterial pathogen present within 5 h, in some cases detecting species which are difficult to culture. For urine samples, we can predict antibiotic sensitivity with up to 95 % accuracy. Skin swabs usually have lower bacterial abundance and higher host DNA, confounding antibiotic sensitivity prediction; an additional host depletion step will likely be required during the processing of these, and other types of samples with high levels of host cell contamination. In summary, our pipeline represents an important step towards the design of individually tailored veterinary treatment plans on the same day as presentation, facilitating the effective use of antibiotics and promoting better antimicrobial stewardship.

Genomic epidemiology of Escherichia coli: antimicrobial resistance through a One Health lens in sympatric humans, livestock and peri-domestic wildlife in Nairobi, Kenya.

BACKGROUND: Livestock systems have been proposed as a reservoir for antimicrobial-resistant (AMR) bacteria and AMR genetic determinants that may infect or colonise humans, yet quantitative evidence regarding their epidemiological role remains lacking. Here, we used a combination of genomics, epidemiology and ecology to investigate patterns of AMR gene carriage in Escherichia coli, regarded as a sentinel organism. METHODS: We conducted a structured epidemiological survey of 99 households across Nairobi, Kenya, and whole genome sequenced E. coli isolates from 311 human, 606 livestock and 399 wildlife faecal samples. We used statistical models to investigate the prevalence of AMR carriage and characterise AMR gene diversity and structure of AMR genes in different host populations across the city. We also investigated household-level risk factors for the exchange of AMR genes between sympatric humans and livestock. RESULTS: We detected 56 unique acquired genes along with 13 point mutations present in variable proportions in human and animal isolates, known to confer resistance to nine antibiotic classes. We find that AMR gene community composition is not associated with host species, but AMR genes were frequently co-located, potentially enabling the acquisition and dispersal of multi-drug resistance in a single step. We find that whilst keeping livestock had no influence on human AMR gene carriage, the potential for AMR transmission across human-livestock interfaces is greatest when manure is poorly disposed of and in larger households. CONCLUSIONS: Findings of widespread carriage of AMR bacteria in human and animal populations, including in long-distance wildlife species, in community settings highlight the value of evidence-based surveillance to address antimicrobial resistance on a global scale. Our genomic analysis provided an in-depth understanding of AMR determinants at the interfaces of One Health sectors that will inform AMR prevention and control.

Epidemiological analysis of Legionnaires' disease in Scotland: a genomic study.

BACKGROUND: Legionella pneumophila is the main cause of a severe pneumonic illness known as Legionnaires' disease and is a global public health threat. Whole-genome sequencing (WGS) can be applied to trace environmental origins of L pneumophila infections, providing information to guide appropriate interventions. We aim to explore the evolutionary and epidemiological relationships in a 36-year Scottish L pneumophila reference isolate collection. METHODS: We investigated the genomic epidemiology of Legionnaires' disease over 36 years in Scotland, comparing genome sequences for all clinical L pneumophila isolates (1984-2020) with a sequence dataset of 3211 local and globally representative isolates. We used a stratified clustering approach to capture epidemiological relationships by core genome Multi-locus Sequence Typing, followed by high-resolution phylogenetic analysis of clusters to measure diversity and evolutionary relatedness in context with epidemiological metadata. FINDINGS: Clustering analysis showed that 111 (57·5 %) of 193 of L pneumophila infections in Scotland were caused by ten endemic lineages with a wide temporal and geographical distribution. Phylogenetic analysis of L pneumophila identified hospital-associated sublineages that had been detected in the hospital environment up to 19 years. Furthermore, 12 (30·0%) of 40 community-associated infections (excluding a single, large outbreak) that occurred over a 13 year period (from 2000 to 2013) were caused by a single widely distributed endemic clone (ST37), consistent with enhanced human pathogenicity. Finally, our analysis revealed clusters linked by national or international travel to distinct geographical regions, indicating several previously unrecognised travel links between closely related isolates (fewer than five single nucleotide polymorphisms) connected by geography. INTERPRETATION: Our analysis reveals the existence of previously undetected endemic clones of L pneumophila that existed for many years in hospital, community, and travel-associated environments. In light of these findings, we propose that cluster and outbreak definitions should be reconsidered, and propose WGS-based surveillance as a critical public health tool for real-time identification and mitigation of clinically important endemic clones. FUNDING: Chief Scientist Office, Biotechnology and Biological Sciences Research Council (UK), Medical Research Council Precision Medicine Doctoral Training Programme, Wellcome Trust, and Medical Research Council (UK).

Repeat infections with chlamydia in women may be more transcriptionally active with lower responses from some immune genes.

Chlamydia trachomatis, the most common bacterial sexually transmitted infection worldwide, is responsible for considerable health burden due to its significant sequelae. There are growing concerns about chlamydial treatment and management due to widely documented increasing burden of repeat infections. In the current study, a cohort study design of 305 women with urogenital chlamydial infections demonstrated that 11.8% of women experienced repeat infections after treatment with azithromycin. The chlamydial DNA load measured by quantitative PCR was higher in women who experienced a repeat infection (p = 0.0097) and repeat infection was associated with sexual contact. There was no genomic or phenotypic evidence of azithromycin resistance within the chlamydial isolates. During repeat infection, or repeat positive tests during follow up, vaginal chlamydial gene expression (ompA, euo, omcB, htrA, trpAB) was markedly higher compared to baseline, and two of the selected immune genes analyzed had significantly lower expression at the time of repeat infection. Overall, there are two implications of these results. The results could be generalized to all recent infections, or repeat positive events, and indicate that chlamydial infections are have higher transcriptional activity of select genes early in the infection in women. Alternatively, after azithromycin treatment, repeat infections of Chlamydia may be more transcriptionally active at certain genes, and there may be post-treatment immunological alterations that interplay into repeat exposures establishing an active infection. The potential that recent infections may involve a higher level of activity from the organism may have implications for management by more regular testing of the most at risk women to reduce the risk of sequelae.

Population genomics of Escherichia coli in livestock-keeping households across a rapidly developing urban landscape.

Quantitative evidence for the risk of zoonoses and the spread of antimicrobial resistance remains lacking. Here, as part of the UrbanZoo project, we sampled Escherichia coli from humans, livestock and peri-domestic wildlife in 99 households across Nairobi, Kenya, to investigate its distribution among host species in this rapidly developing urban landscape. We performed whole-genome sequencing of 1,338 E. coli isolates and found that the diversity and sharing patterns of E. coli were heavily structured by household and strongly shaped by host type. We also found evidence for inter-household and inter-host sharing and, importantly, between humans and animals, although this occurs much less frequently. Resistome similarity was differently distributed across host and household, consistent with being driven by shared exposure to antimicrobials. Our results indicate that a large, epidemiologically structured sampling framework combined with WGS is needed to uncover strain-sharing events among different host populations in complex environments and the major contributing pathways that could ultimately drive the emergence of zoonoses and the spread of antimicrobial resistance.

Emergence and impact of oprD mutations in Pseudomonas aeruginosa strains in cystic fibrosis.

BACKGROUND: Antimicrobial resistance in cystic fibrosis (CF) Pseudomonas aeruginosa airway infection is complex and often attributed to chromosomal mutations. How these mutations emerge in specific strains or whether particular gene mutations are clinically informative is unclear. This study focused on oprD, which encodes an outer membrane porin associated with carbapenem resistance when it is downregulated or inactivated. AIM: Determine how mutations in oprD emerge in two prevalent Australian shared CF strains of P. aeruginosa and their clinical relevance. METHODS: The two most common shared CF strains in Queensland were investigated using whole genome sequencing and their oprD sequences and antimicrobial resistance phenotypes were established. P. aeruginosa mutants with the most common oprD variants were constructed and characterised. Clinical variables were compared between people with or without evidence of infection with strains harbouring these variants. RESULTS: Frequently found nonsense mutations arising from a 1-base pair substitution in oprD evolved independently in three sub-lineages, and are likely major contributors to the reduced carbapenem susceptibility observed in the clinical isolates. Lower baseline FEV1 %predicted was identified as a risk factor for infection with a sub-lineage (odds ratio=0.97; 95% confidence interval 0.96-0.99; p<0.001). However, acquiring these sub-lineage strains did not confer an accelerated decline in FEV1 nor increase the risk of death/lung transplantation. CONCLUSIONS: Sub-lineages harbouring specific mutations in oprD have emerged and persisted in the shared strain populations. Infection with the sub-lineages was more likely in people with lower lung function, but this was not predictive of a worse clinical trajectory.

Population analysis of Legionella pneumophila reveals a basis for resistance to complement-mediated killing.

Legionella pneumophila is the most common cause of the severe respiratory infection known as Legionnaires' disease. However, the microorganism is typically a symbiont of free-living amoeba, and our understanding of the bacterial factors that determine human pathogenicity is limited. Here we carried out a population genomic study of 902 L. pneumophila isolates from human clinical and environmental samples to examine their genetic diversity, global distribution and the basis for human pathogenicity. We find that the capacity for human disease is representative of the breadth of species diversity although some clones are more commonly associated with clinical infections. We identified a single gene (lag-1) to be most strongly associated with clinical isolates. lag-1, which encodes an O-acetyltransferase for lipopolysaccharide modification, has been distributed horizontally across all major phylogenetic clades of L. pneumophila by frequent recent recombination events. The gene confers resistance to complement-mediated killing in human serum by inhibiting deposition of classical pathway molecules on the bacterial surface. Furthermore, acquisition of lag-1 inhibits complement-dependent phagocytosis by human neutrophils, and promoted survival in a mouse model of pulmonary legionellosis. Thus, our results reveal L. pneumophila genetic traits linked to disease and provide a molecular basis for resistance to complement-mediated killing.

Secrets of the Hospital Underbelly: Patterns of Abundance of Antimicrobial Resistance Genes in Hospital Wastewater Vary by Specific Antimicrobial and Bacterial Family.

Background: Hospital wastewater is a major source of antimicrobial resistance (AMR) outflow into the environment. This study uses metagenomics to study how hospital clinical activity impacts antimicrobial resistance genes (ARGs) abundances in hospital wastewater. Methods: Sewage was collected over a 24-h period from multiple wastewater collection points (CPs) representing different specialties within a tertiary hospital site and simultaneously from community sewage works. High throughput shotgun sequencing was performed using Illumina HiSeq4000. ARG abundances were correlated to hospital antimicrobial usage (AMU), data on clinical activity and resistance prevalence in clinical isolates. Results: Microbiota and ARG composition varied between CPs and overall ARG abundance was higher in hospital wastewater than in community influent. ARG and microbiota compositions were correlated (Procrustes analysis, p=0.014). Total antimicrobial usage was not associated with higher ARG abundance in wastewater. However, there was a small positive association between resistance genes and antimicrobial usage matched to ARG phenotype (IRR 1.11, CI 1.06-1.16, p<0.001). Furthermore, analyzing carbapenem and vancomycin resistance separately indicated that counts of ARGs to these antimicrobials were positively associated with their increased usage [carbapenem rate ratio (RR) 1.91, 95% CI 1.01-3.72, p=0.07, and vancomycin RR 10.25, CI 2.32-49.10, p<0.01]. Overall, ARG abundance within hospital wastewater did not reflect resistance patterns in clinical isolates from concurrent hospital inpatients. However, for clinical isolates of the family Enterococcaceae and Staphylococcaceae, there was a positive relationship with wastewater ARG abundance [odds ratio (OR) 1.62, CI 1.33-2.00, p<0.001, and OR 1.65, CI 1.21-2.30, p=0.006 respectively]. Conclusion: We found that the relationship between hospital wastewater ARGs and antimicrobial usage or clinical isolate resistance varies by specific antimicrobial and bacterial family studied. One explanation, we consider is that relationships observed from multiple departments within a single hospital site will be detectable only for ARGs against parenteral antimicrobials uniquely used in the hospital setting. Our work highlights that using metagenomics to identify the full range of ARGs in hospital wastewater is a useful surveillance tool to monitor hospital ARG carriage and outflow and guide environmental policy on AMR.

Evolutionary and Functional Analysis of Coagulase Positivity among the Staphylococci.

The bacterial genus Staphylococcus comprises a large group of pathogenic and nonpathogenic species associated with an array of host species. Staphylococci are differentiated into coagulase-positive or coagulase-negative groups based on the capacity to promote clotting of plasma, a phenotype historically associated with the ability to cause disease. However, the genetic basis of this important diagnostic and pathogenic trait across the genus has not been examined to date. Here, we selected 54 representative staphylococcal species and subspecies to examine coagulation of plasma derived from six representative host species. In total, 13 staphylococcal species mediated coagulation of plasma from at least one host species including one previously identified as coagulase negative (Staphylococcus condimenti). Comparative genomic analysis revealed that coagulase activity correlated with the presence of a gene (vwb) encoding the von Willebrand binding protein (vWbp) whereas only the Staphylococcus aureus complex contained a gene encoding staphylocoagulase (Coa), the classical mediator of coagulation. Importantly, S. aureus retained vwb-dependent coagulase activity in an S. aureus strain deleted for coa whereas deletion of vwb in Staphylococcus pseudintermedius resulted in loss of coagulase activity. Whole-genome-based phylogenetic reconstruction of the Staphylococcus genus revealed that the vwb gene has been acquired on at least four different occasions during the evolution of the Staphylococcus genus followed by allelic diversification via mutation and recombination. Allelic variants of vWbp from selected coagulase-positive staphylococci mediated coagulation in a host-dependent manner indicative of host-adaptive evolution. Taken together, we have determined the genetic and evolutionary basis of staphylococcal coagulation, revealing vWbp to be its archetypal determinant. IMPORTANCE The ability of some species of staphylococci to promote coagulation of plasma is a key pathogenic and diagnostic trait. Here, we provide a comprehensive analysis of the coagulase positivity of the staphylococci and its evolutionary genetic basis. We demonstrate that the von Willebrand binding protein rather than staphylocoagulase is the archetypal coagulation factor of the staphylococci and that the vwb gene has been acquired several times independently during the evolution of the staphylococci. Subsequently, vwb has undergone adaptive diversification to facilitate host-specific functionality. Our findings provide important insights into the evolution of pathogenicity among the staphylococci and the genetic basis for a defining diagnostic phenotype.

Radical genome remodelling accompanied the emergence of a novel host-restricted bacterial pathogen.

The emergence of new pathogens is a major threat to public and veterinary health. Changes in bacterial habitat such as a switch in host or disease tropism are typically accompanied by genetic diversification. Staphylococcus aureus is a multi-host bacterial species associated with human and livestock infections. A microaerophilic subspecies, Staphylococcus aureus subsp. anaerobius, is responsible for Morel's disease, a lymphadenitis restricted to sheep and goats. However, the evolutionary history of S. aureus subsp. anaerobius and its relatedness to S. aureus are unknown. Population genomic analyses of clinical S. aureus subsp. anaerobius isolates revealed a highly conserved clone that descended from a S. aureus progenitor about 1000 years ago before differentiating into distinct lineages that contain African and European isolates. S. aureus subsp. anaerobius has undergone limited clonal expansion, with a restricted population size, and an evolutionary rate 10-fold slower than S. aureus. The transition to its current restricted ecological niche involved acquisition of a pathogenicity island encoding a ruminant host-specific effector of abscess formation, large chromosomal re-arrangements, and the accumulation of at least 205 pseudogenes, resulting in a highly fastidious metabolism. Importantly, expansion of ~87 insertion sequences (IS) located largely in intergenic regions provided distinct mechanisms for the control of expression of flanking genes, including a novel mechanism associated with IS-mediated anti-anti-sense decoupling of ancestral gene repression. Our findings reveal the remarkable evolutionary trajectory of a host-restricted bacterial pathogen that resulted from extensive remodelling of the S. aureus genome through an array of diverse mechanisms in parallel.

Transmission, adaptation and geographical spread of the Pseudomonas aeruginosa Liverpool epidemic strain.

The Liverpool epidemic strain (LES) is an important transmissible clonal lineage of Pseudomonas aeruginosa that chronically infects the lungs of people with cystic fibrosis (CF). Previous studies have focused on the genomics of the LES in a limited number of isolates, mostly from one CF centre in the UK, and from studies highlighting identification of the LES in Canada. Here we significantly extend the current LES genome database by genome sequencing 91 isolates from multiple CF centres across the UK, and we describe the comparative genomics of this large collection of LES isolates from the UK and Canada. Phylogenetic analysis revealed that the 145 LES genomes analysed formed a distinct clonal lineage when compared with the wider P. aeruginosa population. Notably, the isolates formed two clades: one associated with isolates from Canada, and the other associated with UK isolates. Further analysis of the UK LES isolates revealed clustering by clinic geography. Where isolates clustered closely together, the association was often supported by clinical data linking isolates or patients. When compared with the earliest known isolate, LESB58 (from 1988), many UK LES isolates shared common loss-of-function mutations, such as in genes gltR and fleR. Other loss-of-function mutations identified in previous studies as common adaptations during CF chronic lung infections were also identified in multiple LES isolates. Analysis of the LES accessory genome (including genomic islands and prophages) revealed variations in the carriage of large genomic regions, with some evidence for shared genomic island/prophage complement according to clinic location. Our study reveals divergence and adaptation during the spread of the LES, within the UK and between continents.

Quantifying the transmission of antimicrobial resistance at the human and livestock interface with genomics.

BACKGROUND: Livestock have been implicated as a reservoir for antimicrobial resistance (AMR) that can spread to humans. Close proximity and ecological interfaces involving livestock have been posited as risk factors for the transmission of AMR. In spite of this, there are sparse data and limited agreement on the transmission dynamics that occur. OBJECTIVES: To identify how genome sequencing approaches can be used to quantify the dynamics of AMR transmission at the human-livestock interface, and where current knowledge can be improved to better understand the impact of transmission on the spread of AMR. SOURCES: Key articles investigating various aspects of AMR transmission at the human-livestock interface are discussed, with a focus on Escherichia coli. CONTENT: We recapitulate the current understanding of the transmission of AMR between humans and livestock based on current genomic and epidemiological approaches. We discuss how the use of well-designed, high-resolution genome sequencing studies can improve our understanding of the human-livestock interface. IMPLICATIONS: A better understanding of the human-livestock interface will aid in the development of evidence-based and effective One Health interventions that can ultimately reduce the burden of AMR in humans.

The Aedes aegypti Domino Ortholog p400 Regulates Antiviral Exogenous Small Interfering RNA Pathway Activity and ago-2 Expression.

Arboviruses are pathogens of humans and animals. A better understanding of the interactions between these pathogens and the arthropod vectors, such as mosquitoes, that transmit them is necessary to develop novel control measures. A major antiviral pathway in the mosquito vector is the exogenous small interfering RNA (exo-siRNA) pathway, which is induced by arbovirus-derived double-stranded RNA in infected cells. Although recent work has shown the key role played by Argonaute-2 (Ago-2) and Dicer-2 (Dcr-2) in this pathway, the regulatory mechanisms that govern these pathways have not been studied in mosquitoes. Here, we show that the Domino ortholog p400 has antiviral activity against the alphavirus Semliki Forest virus (Togaviridae) both in Aedes aegypti-derived cells and in vivo Antiviral activity of p400 was also demonstrated against chikungunya virus (Togaviridae) and Bunyamwera virus (Peribunyaviridae) but not Zika virus (Flaviviridae). p400 was found to be expressed across mosquito tissues and regulated ago-2 but not dcr-2 transcript levels in A. aegypti mosquitoes. These findings provide novel insights into the regulation of an important aedine exo-siRNA pathway effector protein, Ago-2, by the Domino ortholog p400. They add functional insights to previous observations of this protein's antiviral and RNA interference regulatory activities in Drosophila melanogasterIMPORTANCE Female Aedes aegypti mosquitoes are vectors of human-infecting arthropod-borne viruses (arboviruses). In recent decades, the incidence of arthropod-borne viral infections has grown dramatically. Vector competence is influenced by many factors, including the mosquito's antiviral defenses. The exogenous small interfering RNA (siRNA) pathway is a major antiviral response restricting arboviruses in mosquitoes. While the roles of the effectors of this pathway, Argonaute-2 and Dicer-2 are well characterized, nothing is known about its regulation in mosquitoes. In this study, we demonstrate that A. aegypti p400, whose ortholog Domino in Drosophila melanogaster is a chromatin-remodeling ATPase member of the Tip60 complex, regulates siRNA pathway activity and controls ago-2 expression levels. In addition, we found p400 to have antiviral activity against different arboviruses. Therefore, our study provides new insights into the regulation of the antiviral response in A. aegypti mosquitoes.

Metagenomic sequencing of clinical samples reveals a single widespread clone of Lawsonia intracellularis responsible for porcine proliferative enteropathy.

Lawsonia intracellularis is a Gram-negative obligate intracellular bacterium that is the aetiological agent of proliferative enteropathy (PE), a common intestinal disease of major economic importance in pigs and other animal species. To date, progress in understanding the biology of L. intracellularis for improved disease control has been hampered by the inability to culture the organism in vitro. In particular, our understanding of the genomic diversity and population structure of clinical L. intercellularis is very limited. Here, we utilized a metagenomic shotgun approach to directly sequence and assemble 21 L. intracellularis genomes from faecal and ileum samples of infected pigs and horses across three continents. Phylogenetic analysis revealed a genetically monomorphic clonal lineage responsible for infections in pigs, with distinct subtypes associated with infections in horses. The genome was highly conserved, with 94 % of genes shared by all isolates and a very small accessory genome made up of only 84 genes across all sequenced strains. In part, the accessory genome was represented by regions with a high density of SNPs, indicative of recombination events importing novel gene alleles. In summary, our analysis provides the first view of the population structure for L. intracellularis, revealing a single major lineage associated with disease of pigs. The limited diversity and broad geographical distribution suggest the recent emergence and clonal expansion of an important livestock pathogen.