Burkholderia pseudomallei is a facultative intracellular bacterial pathogen that causes melioidosis, a severe invasive disease of humans. We previously reported that the stress-related catecholamine ...hormone epinephrine enhances motility of B. pseudomallei, transcription of flagellar genes and the production of flagellin. It has been reported that the QseBC two-component sensory system regulates motility and virulence-associated genes in other Gram-negative bacteria in response to stress-related catecholamines, albeit disparities between studies exist. We constructed and whole-genome sequenced a mutant of B. pseudomallei with a deletion spanning the predicted qseBC homologues (bpsl0806 and bpsl0807). The ΔqseBC mutant exhibited significantly reduced swimming and swarming motility and reduced transcription of fliC. It also exhibited a defect in biofilm formation and net intracellular survival in J774A.1 murine macrophage-like cells. While epinephrine enhanced bacterial motility and fliC transcription, no further reduction in these phenotypes was observed with the ΔqseBC mutant in the presence of epinephrine. Plasmid-mediated expression of qseBC suppressed bacterial growth, complicating attempts to trans-complement mutant phenotypes. Our data support a role for QseBC in motility, biofilm formation and net intracellular survival of B. pseudomallei, but indicate that it is not essential for epinephrine-induced motility per se.
•Genomic signatures of host-adaptation and virulence of Salmonella are emerging.•Sequence analyses can aid the prediction of zoonotic risk and source attribution.•Host-specific, niche-specific and ...variant-specific virulence factors have been identified.•Comparative and functional genomics identify options for control of Salmonella.•Rodent and cell-based assays do not always reflect salmonellosis in farm animals.
Salmonella is an animal and zoonotic pathogen of global importance. Depending on pathogen and host factors, infections can be asymptomatic or involve acute gastroenteritis or invasive disease. Genomic signatures associated with host-range, tissue tropism or differential virulence of Salmonella enterica serovars, and their variants, have emerged. In turn, it is becoming feasible to predict invasive potential, host-adaptation and zoonotic risk of Salmonella from sequence data to improve outbreak investigation, risk assessment and control strategies. Functional annotation of Salmonella genomes has accelerated with the screening of high-density mutant libraries, revealing host-specific, niche-specific and serovar-specific virulence factors. As natural hosts and reservoirs, farmed animals provide powerful insights into host-adaptation and pathogenesis of Salmonella not always evident from surrogate rodent or cell-based models.
Avian pathogenic Escherichia coli (APEC) cause colibacillosis in birds, a syndrome of severe respiratory and systemic disease that constitutes a major threat due to early mortality, condemnation of ...carcasses and reduced productivity. APEC can infect different types of birds in all commercial settings, and birds of all ages, although disease tends to be more severe in younger birds likely a consequence of an immature immune system. APEC can act as both primary and secondary pathogens, with predisposing factors for secondary infections including poor housing conditions, respiratory viral and Mycoplasma spp. infections or vaccinations. Controlled studies with APEC as primary pathogens have been used to study the bird's immune response to APEC, although it may not always be representative of natural infections which may be more complex due to the presence of secondary agents, stress and environmental factors. Under controlled experimental conditions, a strong early innate immune response is induced which includes host defence peptides in mucus and a cellular response driven by heterophils and macrophages. Both antibody and T-cell mediated adaptive responses have been demonstrated after vaccination. In this review we will discuss the bird's immune response to APEC as primary pathogen with a bias towards the innate immune response, as mechanistic adaptive studies clearly form a much more limited body of work despite numerous vaccine trials.
Microglia have critical roles in neural development, homeostasis and neuroinflammation and are increasingly implicated in age-related neurological dysfunction. Neurodegeneration often occurs in ...disease-specific, spatially restricted patterns, the origins of which are unknown. We performed to our knowledge the first genome-wide analysis of microglia from discrete brain regions across the adult lifespan of the mouse, and found that microglia have distinct region-dependent transcriptional identities and age in a regionally variable manner. In the young adult brain, differences in bioenergetic and immunoregulatory pathways were the major sources of heterogeneity and suggested that cerebellar and hippocampal microglia exist in a more immune-vigilant state. Immune function correlated with regional transcriptional patterns. Augmentation of the distinct cerebellar immunophenotype and a contrasting loss in distinction of the hippocampal phenotype among forebrain regions were key features during aging. Microglial diversity may enable regionally localized homeostatic functions but could also underlie region-specific sensitivities to microglial dysregulation and involvement in age-related neurodegeneration.
The cecal microbiota plays numerous roles in chicken health and nutrition. Where such microbiota differs between lines exhibiting distinct phenotypes, microbiota transplantation offers scope to ...dissect the role of gut microbial communities in those traits. However, the composition and stability of transplants over time is relatively ill-defined and varying levels of success have been reported. In this study, we transplanted cecal contents from adult Roslin broilers into chicks from a different broiler line. Within <12 h posthatch, Ross 308 chicks received an oral gavage of cecal contents (n = 26) or a PBS control (n = 24). Cecal contents samples were collected postmortem from birds on d 1, 2, 3, 4, and 7 posthatch. DNA was extracted from these samples and the transplant inoculum and the V4 region of the 16S rRNA gene was amplified and sequenced. The cecal microbiota of chickens receiving the microbiota transplant was significantly different in composition and significantly richer and more diverse, in comparison to control birds. At the final timepoint (d 7), of the 150 Operational Taxonomic Units (OTUs) that were >0.1% abundant (average) in the donor sample, 137 were detected in the treated group (75 were >0.1% abundant (average)) while only 88 were detected in the control group (29 were >0.1% abundant (average)). Our data therefore suggests that stable transplantation of the cecal microbiota between lines is achievable using the methods described in this paper.
Two lineages of Salmonella enterica serovar Typhimurium (S. Typhimurium) of multi-locus sequence type ST313 have been linked with the emergence of invasive Salmonella disease across sub-Saharan ...Africa. The expansion of these lineages has a temporal association with the HIV pandemic and antibiotic usage. We analysed the whole genome sequence of 129 ST313 isolates representative of the two lineages and found evidence of lineage-specific genome degradation, with some similarities to that observed in S. Typhi. Individual ST313 S. Typhimurium isolates exhibit a distinct metabolic signature and modified enteropathogenesis in both a murine and cattle model of colitis, compared to S. Typhimurium outside of the ST313 lineages. These data define phenotypes that distinguish ST313 isolates from other S. Typhimurium and may represent adaptation to a distinct pathogenesis and lifestyle linked to an-immuno-compromised human population.
Avian colibacillosis is caused by a group of pathogens designated avian pathogenic Escherichia coli (APEC). Despite being known for over a century, avian colibacillosis remains one of the major ...endemic diseases afflicting the poultry industry worldwide. Autologous bacterins provide limited serotype-specific protection, yet multiple serogroups are associated with disease, especially O1, O2 and O78 among many others. Experimental infection models have facilitated the identification of some key APEC virulence genes and have allowed testing of vaccine candidates. Well-recognized virulence factors include Type 1 (F1) and P (Pap/Prs) fimbriae for colonization, IbeA for invasion, iron acquisition systems, TraT and Iss for serum survival, K and O antigens for anti-phagocytic activity, and a temperature-sensitive haemagglutinin of imprecise function. Intriguingly, these factors do not occur universally among APEC, suggesting the presence of multiple alternative mechanisms mediating pathogenicity. The recent availability of the first complete APEC genome sequence can be expected to accelerate the identification of bacterial genes expressed during infection and required for virulence. High-throughput molecular approaches like signature-tagged transposon mutagenesis have already proved invaluable in revealing portfolios of genes expressed by pathogenic bacteria during infection, and this has enabled identification of APEC O2 factors required for septicaemia in the chicken model. Complimentary approaches, such as in vivo-induced antigen technology, exist to define the activities of APEC in vivo. In recent years, reverse vaccinology and immuno-proteomic approaches have also enabled identification of novel vaccine candidates in other bacterial pathogens. Collectively, such information provides the basis for the development or improvement of strategies to control APEC infections in the food-producing avian species.
Summary Background In South Africa, sputum smear microscopy has been replaced with Xpert MTB/RIF as the initial diagnostic test for tuberculosis. In a pragmatic parallel cluster-randomised trial, we ...evaluated the effect on patient and programme outcomes. Methods We randomly allocated 20 laboratories (clusters) in medium-burden districts of South Africa to either an Xpert (immediate Xpert) or microscopy (Xpert deferred) group (1:1), stratified by province. At two primary care clinics per laboratory, a systematic sample of adults giving sputum for tuberculosis investigation was assessed for eligibility. The primary outcome was mortality at 6 months from enrolment. Masking of participants' group allocation was not possible because of the pragmatic trial design. The trial is registered with the ISRCTN registry (ISRCTN68905568) and the South African Clinical Trial Register (DOH-27-1011-3849). Findings Between June and November, 2012, 4972 people were screened, and 4656 (93·6%) enrolled (median age 36 years; 2891 62% female; 2212 62% reported being HIV-positive). There was no difference between the Xpert and microscopy groups with respect to mortality at 6 months (91/2324 3·9% vs 116/2332 5·0%, respectively; adjusted risk ratio aRR 1·10, 95% CI 0·75–1·62). Interpretation Xpert did not reduce mortality at 6 months compared with sputum microscopy. Improving outcomes in drug-sensitive tuberculosis programmes might require not only better diagnostic tests but also better linkage to care. Funding Bill & Melinda Gates Foundation.
Campylobacter is the leading cause of bacterial foodborne gastroenteritis worldwide. Handling or consumption of contaminated poultry meat is a key risk factor for human campylobacteriosis. One ...potential control strategy is to select poultry with increased resistance to Campylobacter. We associated high-density genome-wide genotypes (600K single nucleotide polymorphisms) of 3000 commercial broilers with Campylobacter load in their caeca. Trait heritability was modest but significant (h
= 0.11 ± 0.03). Results confirmed quantitative trait loci (QTL) on chromosomes 14 and 16 previously identified in inbred chicken lines, and detected two additional QTLs on chromosomes 19 and 26. RNA-Seq analysis of broilers at the extremes of colonisation phenotype identified differentially transcribed genes within the QTL on chromosome 16 and proximal to the major histocompatibility complex (MHC) locus. We identified strong cis-QTLs located within MHC suggesting the presence of cis-acting variation in MHC class I and II and BG genes. Pathway and network analyses implicated cooperative functional pathways and networks in colonisation, including those related to antigen presentation, innate and adaptive immune responses, calcium, and renin-angiotensin signalling. While co-selection for enhanced resistance and other breeding goals is feasible, the frequency of resistance-associated alleles was high in the population studied and non-genetic factors significantly influenced Campylobacter colonisation.
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