Virulence In Animals Research Articles

Avirulence of a spontaneous Francisella tularensis subsp. mediasiatica prmA mutant.

Francisella tularensis, the causative agent of tularemia, is divided into three subspecies. Two of these, subspecies holarctica and tularensis, are highly pathogenic to humans and consequently relatively well studied. The third subspecies, mediasiatica, is rarely isolated and remains poorly studied. It is distributed in the sparsely populated regions of Central Asia and Siberia. Curently this subspecies is not known to have been responsible for human infections in spite of its high virulence in laboratory animals. Subspecies mediasiatica is currently divided into three subgroups-MI, present in Central Asia, MII, present in southern Siberia, and MIII represented by a unique strain, 60(B)57, isolated in Uzbekistan in 1960. We describe here the unexpected observation that MIII strain 60(B)57 is avirulent and immunogenic. We observed that infection with this strain protected mice from challenge 21 days later with a virulent subsp. mediasiatica strain. With an increase of this interval, the protection for mice was significantly reduced. In contrast, guinea pigs were protected from challenge with strains of the subspecies holarctica and mediasiatica (but not subsp. tularensis) 90 days after infection with 60(B)57. We performed genome assembly based on whole genome sequencing data obtained using the Nanopore MinION for strain 60(B)57 and two subsp. mediasiatica strains representing the Central Asian MI and Siberian MII phylogenetic subgroups. The prmA gene is truncated due to a nonsense mutation in strain 60(B)57. The deletion of gene prmA has previously been shown to induce a loss of virulence in Francisella novicida the closest model organism suggesting that the observed mutation might the cause of the avirulence of strain 60(B)57.

Pseudomonas aeruginosa: Prevalence in Human and Animal Products, Virulence and Antibiotic Resistance Aspects

Pseudomonas aeruginosa (P. aeruginosa) is considered as pathogen that able to cause a number of diseases syndromes in the community and in hospitals. According to reports, the virulence factors and antibiotic resistances of P. aeruginosa it seem to consider them challenging to treat. The current review try to spot high lights on the prevalence of P. aeruginosa from various sources, in addition to assess the risk to the public's health, and concreted the definitive way for a diagnosis. This will help the medical staff to create a surveillance system and enhance infection control procedures.

Brucella melitensis Vaccines: A Systematic Review

Background: Brucella melitensis is recognized as one of the predominant zoonotic pathogens globally. Live-attenuated vaccine Rev 1 is currently the most effective vaccine for controlling B. melitensis in small ruminants. While Brucella inactivated, nanoparticle, and subunit vaccines are less effective and require multiple doses, live-attenuated vaccines are less expensive and more efficacious. Several drawbacks are associated with the administration of current attenuated B. melitensis vaccines, including interference with serological diagnostic tests, inducing abortion in pregnant animals, shedding in milk, and zoonotic infections in humans. In this systematic review, we summarize the current literature (1970–2022) on B. melitensis vaccines and review their advantages and disadvantages in order to support the rationale for a need for new or improved small ruminant brucellosis vaccines. Methods: A systematic search was carried out in Web of Science, CAB Abstracts, and PubMed. The original articles describing the B. melitensis vaccines were included. Review articles, articles not published in English, articles that did not offer full text, editorials, correspondences, case reports, case series, diagnostic tests, duplicate publications, and other Brucella vaccines (e.g., B. abortus and B. suis) were excluded. Results: Out of 3700 studies, we identified 18 articles that evaluated B. meltensis vaccines, including recombinant B. melitensis strains (16MΔhfq, 16MΔTcfSR, M5-90ΔmanB, LVM31, M5-90ΔvjbR, 16MΔmucR, ΔznuA, M5-90Δpgm, M5-90ΔwboA), live B. melitensis strain (Rev 1), nanoparticle vaccines (B. melitensis 16M, B. melitensis OMP 31, FliC protein—Mannosylated Chitosan Nanoparticles (FliC and FliC-MCN), B. melitensis and B. abortus combined, and B. melitensis 16M nanoparticles combined with oligopolysaccharide), subunit vaccines (outer membrane vesicles or outer membrane proteins), and a DNA vaccine based on B. melitensis outer membrane proteins (Omp25 and Omp31). The results from these studies revealed that these vaccines can induce humoral and cellular responses and reduce macrophage survival. However, most of these vaccines were evaluated only in murine models, which may not accurately reflect how they work in natural hosts. Conclusions: The high prevalence of B. melitensis in humans and animals remains an issue in many parts of the world. Human brucellosis can be prevented by controlling brucellosis in livestock using vaccination and test-and-removal strategies. Prospective vaccines have limitations, including interference with serodiagnostics after vaccination, virulence in humans and animals, the requirement of booster vaccinations, and insufficient efficacy in preventing infection or abortion. Moreover, most of these vaccines have been assessed in mice models, which have failed to predict immunogenicity or efficacy in natural hosts. Because of these limitations and the re-emergence of B. melitensis worldwide with a high incidence of human infection, our review suggests a need for additional research into the molecular pathology and immunological properties of B. melitensis infection and the identification of protective epitopes or genes that would allow for the development of improved vaccines for small ruminants.

Amoeba predation of Cryptococcus: A quantitative and population genomic evaluation of the accidental pathogen hypothesis.

The "Amoeboid Predator-Fungal Animal Virulence Hypothesis" posits that interactions with environmental phagocytes shape the evolution of virulence traits in fungal pathogens. In this hypothesis, selection to avoid predation by amoeba inadvertently selects for traits that contribute to fungal escape from phagocytic immune cells. Here, we investigate this hypothesis in the human fungal pathogens Cryptococcus neoformans and Cryptococcus deneoformans. Applying quantitative trait locus (QTL) mapping and comparative genomics, we discovered a cross-species QTL region that is responsible for variation in resistance to amoeba predation. In C. neoformans, this same QTL was found to have pleiotropic effects on melanization, an established virulence factor. Through fine mapping and population genomic comparisons, we identified the gene encoding the transcription factor Bzp4 that underlies this pleiotropic QTL and we show that decreased expression of this gene reduces melanization and increases susceptibility to amoeba predation. Despite the joint effects of BZP4 on amoeba resistance and melanin production, we find no relationship between BZP4 genotype and escape from macrophages or virulence in murine models of disease. Our findings provide new perspectives on how microbial ecology shapes the genetic architecture of fungal virulence, and suggests the need for more nuanced models for the evolution of pathogenesis that account for the complexities of both microbe-microbe and microbe-host interactions.

A multidrug-resistant Salmonella enterica Typhimurium DT104 complex lineage circulating among humans and cattle in the USA lost the ability to produce pertussis-like toxin ArtAB.

Salmonella enterica subsp. enterica serotype Typhimurium definitive type 104 (DT104) can infect both humans and animals and is often multidrug-resistant (MDR). Previous studies have indicated that, unlike most S. Typhimurium, the overwhelming majority of DT104 strains produce pertussis-like toxin ArtAB via prophage-encoded genes artAB. However, DT104 that lack artAB have been described on occasion. Here, we identify an MDR DT104 complex lineage circulating among humans and cattle in the USA, which lacks artAB (i.e. the ‘U.S. artAB-negative major clade’; n=42 genomes). Unlike most other bovine- and human-associated DT104 complex strains from the USA (n=230 total genomes), which harbour artAB on prophage Gifsy-1 (n=177), members of the U.S. artAB-negative major clade lack Gifsy-1, as well as anti-inflammatory effector gogB. The U.S. artAB-negative major clade encompasses human- and cattle-associated strains isolated from ≥11 USA states over a 20-year period. The clade was predicted to have lost artAB, Gifsy-1 and gogB circa 1985–1987 (95 % highest posterior density interval 1979.0–1992.1). When compared to DT104 genomes from other regions of the world (n=752 total genomes), several additional, sporadic artAB, Gifsy-1 and/or gogB loss events among clades encompassing five or fewer genomes were observed. Using phenotypic assays that simulate conditions encountered during human and/or bovine digestion, members of the U.S. artAB-negative major clade did not differ from closely related Gifsy-1/artAB/gogB-harbouring U.S. DT104 complex strains (ANOVA raw P>0.05); thus, future research is needed to elucidate the roles that artAB, gogB and Gifsy-1 play in DT104 virulence in humans and animals.

Cell wall composition in Cryptococcus neoformans is media dependent and alters host response, inducing protective immunity.

Cryptococcus neoformans is a basidiomycete fungus that can cause meningoencephalitis, especially in immunocompromised patients. Cryptococcus grows in many different media, although little attention has been paid to the role of growth conditions on the cryptococcal cell wall or on virulence. The purpose of this study was to determine how different media influenced the amount of chitin and chitosan in the cell wall, which in turn impacted the cell wall architecture and host response. Yeast extract, peptone, and dextrose (YPD) and yeast nitrogen base (YNB) are two commonly used media for growing Cryptococcus before use in in vitro or in vivo experiments. As a result, C. neoformans was grown in either YPD or YNB, which were either left unbuffered or buffered to pH 7 with MOPS. These cells were then labeled with cell wall-specific fluorescent probes to determine the amounts of various cell wall components. In addition, these cells were employed in animal virulence studies using the murine inhalation model of infection. We observed that the growth of wild-type C. neoformans KN99 significantly changes the pH of unbuffered media during growth. It raises the pH to 8.0 when grown in unbuffered YPD but lowers the pH to 2.0 when grown in unbuffered YNB (YNB-U). Importantly, the composition of the cell wall was substantially impacted by growth in different media. Cells grown in YNB-U exhibited a 90% reduction in chitosan, the deacetylated form of chitin, compared with cells grown in YPD. The decrease in pH and chitosan in the YNB-U-grown cells was associated with a significant increase in some pathogen-associated molecular patterns on the surface of cells compared with cells grown in YPD or YNB, pH 7. This altered cell wall architecture resulted in a significant reduction in virulence when tested using a murine model of infection. Furthermore, when heat-killed cells were used as the inoculum, KN99 cells grown in YNB-U caused an aberrant hyper-inflammatory response in the lungs, resulting in rapid animal death. In contrast, heat-killed KN99 cells grown in YNB, pH 7, caused little to no inflammatory response in the host lung, but, when used as a vaccine, they conferred a robust protective response against a subsequent challenge infection with the virulent KN99 cells. These findings emphasize the importance of culture media and pH during growth in shaping the content and organization of the C. neoformans cell wall, as well as their impact on fungal virulence and the host response.

Bm Delta-pgm, a vaccine for the control of Brucella melitensis with cross-species protective properties.

Brucellosis remains one of the most worldwide distributed zoonosis inflicting serious economical and human health problems in many areas of the world. The disease is caused by different species of the genus Brucella that have different tropisms towards different mammals being the most relevant for human health Brucella abortus, Brucella melitensis and Brucella suis that infect cows, goats/sheep, and swine respectively. For B. melitensis, considered the species with more zoonotic potential and highly aggressive for animals, only one vaccine is available to date in the market: Rev 1. This attenuated strain has the disadvantage that is has a very high residual virulence for animals and humans and, for this reason, it is applied by ocular instillation which is technically challenging in many productive settings. For this reason, the search for new vaccines for caprine and ovine brucellosis is an active topic of research. We describe here the construction of a novel highly attenuated vaccine strain (Bm Delta-pgm) that confers excellent levels of protection against B. melitensis in the mouse model of infection. This strain is a clean deletion of the phosphoglucomutase (pgm) gene that codes for a protein that catalyzes the conversion of glucose-6-P to glucose-1-P, which is used as a precursor for the biosynthesis of many polysaccharides, including the O-antigen of the lipopolysaccharide and cyclic beta glucans. Our results indicate that vaccination with Bm Delta-pgm induces a robust memory cellular immune response but no antibody production against the O-antigen. Cross protection experiments show that this new vaccine protects against B. abortus and B. suis raising the possibility that Bm Delta-pgm could be used as a universal vaccine for the most important Brucella species.

Similar evolutionary trajectories in an environmental Cryptococcus neoformans isolate after human and murine infection

A pet cockatoo was the suspected source of Cryptococcus neoformans recovered from an immunocompromised patient with cryptococcosis based on molecular analyses available in 2000. Here, we report whole genome sequence analysis of the clinical and cockatoo strains. Both are closely related MATα strains belonging to the VNII lineage, confirming that the human infection likely originated from pet bird exposure. The two strains differ by 61 single nucleotide polymorphisms, including eight nonsynonymous changes involving seven genes. To ascertain whether changes in these genes are selected for during mammalian infection, we passaged the cockatoo strain in mice. Remarkably, isolates obtained from mouse tissue possess a frameshift mutation in one of the seven genes altered in the human sample (LQVO5_000317), a gene predicted to encode an SWI-SNF chromatin-remodeling complex protein. In addition, both cockatoo and patient strains as well as mouse-passaged isolates obtained from brain tissue had a premature stop codon in a homologue of ZFC3 (LQVO5_004463), a predicted single-zinc finger containing protein, which is associated with larger capsules when deleted and reverted to a full-length protein in the mouse-passaged isolates obtained from lung tissue. The patient strain and mouse-passaged isolates show variability in virulence factors, with differences in capsule size, melanization, rates of nonlytic expulsion from macrophages, and amoeba predation resistance. Our results establish that environmental strains undergo genomic and phenotypic changes during mammalian passage, suggesting that animal virulence can be a mechanism for genetic change and that the genomes of clinical isolates may provide a readout of mutations acquired during infection.

The ColR/S two-component system is a conserved determinant of host association across Pseudomonas species.

Members of the bacterial genus Pseudomonas form mutualistic, commensal, and pathogenic associations with diverse hosts. The prevalence of host association across the genus suggests that symbiosis may be a conserved ancestral trait and that distinct symbiotic lifestyles may be more recently evolved. Here we show that the ColR/S two-component system, part of the Pseudomonas core genome, is functionally conserved between Pseudomonas aeruginosa and Pseudomonas fluorescens. Using plant rhizosphere colonization and virulence in a murine abscess model, we show that colR is required for commensalism with plants and virulence in animals. Comparative transcriptomics revealed that the ColR regulon has diverged between P. aeruginosa and P. fluorescens and deleting components of the ColR regulon revealed strain-specific, but not host-specific, requirements for ColR-dependent genes. Collectively, our results suggest that ColR/S allows Pseudomonas to sense and respond to a host, but that the ColR-regulon has diverged between Pseudomonas strains with distinct lifestyles. This suggests that conservation of two-component systems, coupled with life-style dependent diversification of the regulon, may play a role in host association and lifestyle transitions.

CRZ1 transcription factor is involved in cell survival, stress tolerance, and virulence in fungi

The calcineurin-CRZ1 signaling pathway is conserved from yeasts to humans, and is involved in survival, tolerance to biotic and abiotic stress conditions, virulence, and drug resistance. The primary target of calcineurin is Crz1p in yeasts and nuclear factor of activated T-cells (NFAT) in mammals. Calcineurin regulates the expression of various genes involved in cell wall regeneration, ionic homeostasis, virulence, and other cellular processes. Another protein called regulator of calcineurin (RCN) also regulates calcineurin functions. This review discusses the structure, functions, and regulations of CRZ1 in fungi and related organisms. We have also discussed the role of CRZ1 in pathogenicity and virulence in fungi, plants, and animals.

A multiplex PCR for the detection of Vibrio vulnificus hazardous to human and/or animal health from seafood

Vibrio vulnificus is a zoonotic pathogen linked to aquaculture that is spreading due to climate change. The pathogen can be transmitted to humans and animals by ingestion of raw shellfish or seafood feed, respectively. The aim of this work was to design and test a new procedure to detect V. vulnificus hazardous to human and/or animal health in food/feed samples. For this purpose, we combined a pre-enrichment step with multiplex PCR using primers for the species and for human and animal virulence markers. In vitro assays with mixed DNA from different Vibrio species and Vibrio cultures showed that the new protocol was 100 % specific with a detection limit of 10 cfu/mL. The protocol was successfully validated in seafood using artificially contaminated live shrimp and proved useful also in pathogen isolation from animals and their ecosystem. In conclusion, this novel protocol could be applied in health risk studies associated with food/feed consumption, as well as in the routine identification and subtyping of V. vulnificus from environmental or clinical samples.

Comparative study of the phenotype and virulence of recent serovar 1a, 1b, and 2a isolates of Erysipelothrix rhusiopathiae in Japan

Erysipelothrix rhusiopathiae causes swine erysipelas (SE) and is classified –into 16 serovars based on cell surface antigens. Our previous study suggested that recent SE outbreaks were mostly caused by serovar 1a of E. rhusiopathiae with the surface protective antigen (Spa)A protein characterized by methionine and isoleucine at positions 203 and 257 (M203/I257 SpaA). In this study, four recent E. rhusiopathiae isolates comprising two serovar 1a with M203/I257 SpaA strains (2012 Miyazaki and 2012 Chiba), one serovar 1b strain (2015 Miyazaki), and one serovar 2a strain (2012 Nagano) were compared with each other and with the serovar 1a Fujisawa reference strain regarding in vitro phenotypes and in vivo virulence in mice and pigs. The serovar 1b and 2a strains, which are the less prevalent strains in the field in Japan, showed lower growth in liquid culture and lower virulence in animals than the serovar 1a variants. Adhesion of the serovar 2a strain to porcine endothelial cells was weaker than that of the serovar 1a and 1b strains. Several advantages of serovar 1a strains were found, but no plausible cause of the M203/I257 SpaA type variants to be selected for the most prevalent strains among serovar 1a strains was identified in this study.

Combined immunization with inactivated vaccine reduces the dose of live B. abortus A19 vaccine

BackgroundBrucella spp. is an important zoonotic pathogen responsible for brucellosis in humans and animals. Brucella abortus A19 strain is a widespread vaccine in China. However, it has a drawback of residual virulence in animals and humans.MethodsIn this study, the BALB/c mice were inoculated with either 100 μL PBS(control group, C group), 109 CFU/mL inactivated B. abortus A19 strain (I group), 105 CFU/mL (low-dose group, L group) 106 CFU/mL live B. abortus A19 strain (high-dose group, H group), or 105 CFU/mL live B. abortus A19 strain combined with 109 CFU/mL inactivated B. abortus A19 strain (LI group). Mice were challenged with B. abortus strain 2308 at 7 week post vaccination. Subsequently, the immune and protective efficacy of the vaccines were evaluated by measuring splenic bacterial burden, spleen weight, serum IgG, interferon-gamma (IFN-γ), interleukin-4 (IL-4) percentage of CD4 + and CD8 + T cells of mice via bacterial isolation, weighing, ELISA and flow cytometry, respectively.ResultsThe splenic bacterial burden and spleen weight of the mice in group LI were mostly equivalent to the mice of group H. Moreover, Brucella-specific serum IgG, IFN-γ, IL-4, and the percentage of CD4+ and CD8+ T cells of the LI group mice were similar to those of the H group. In the subsequent challenge test, both vaccines conferred protective immunity to wild-type (WT) 2308 strain. In addition, the levels of IL-4 and IFN-γ, CD4+ and CD8+ T cells in these mice were similar to those of the mice in the H group.ConclusionsCombined immunization with low dose live vaccine and inactivated vaccine allowed to reduce the live B. abortus A19 vaccine, dose with an equivalent protection of the high-dose live vaccine.

On the issue of isolating a pure culture of the causative agent of pasteurellosis Pasteurella Multocida

The article presents an analytical review on the isolation of a pure culture of the pasteurellosis pathogen Pasteurella multocida according to literature data and the results of our own research. On the basis of new knowledge in the etiology of pasteurellosis, the disadvantages of the traditional method have been identified and the fundamental distinctive features of a new technical solution for the method of isolating a pure culture of P. multocida of the first generation after in vivo have been established. For its application, a standard of conditions has been formulated. To ensure the uniformity of the conditions of the methodology for the isolation, assessment and application of a pure culture (strain) of the P. multocida pasteurellosis pathogen, a method (standard) has been developed and proposed for laboratory practice. The method, including obtaining the first generation of a microorganism on an artificial environment, differs in that an individual infected naturally or intranasally or orally on the mucous membrane of the nasal, oral, pharyngeal cavities and an individual selected from a bird or rabbit, which has died from pasteurellosis, weighing 350 g after 3 h (at 20 ± 1 ° C of cooling the corpse), open, take a blood sample from the heart and add it to sterile water at a temperature of 20 ± 1 ° C in a ratio of 1: 9 by volume, shake the precipitate and transfer to a suspension, then centrifuge at 1500 rpm/ min 5 min; the supernatant liquid as a pasteurella isolate from blood in a dilution of 10-1 is diluted to 10-2, 10- 3 and inoculated at a temperature of 20±1°C on nutrient broth and nutrient agar, the crops are cultivated for 9-19 h at 37°C and 1 h at 20°C. The resulting culture is assessed pure according to strictly typical morphology of continuous growth and uniform colonies of the S-form, identical cocco- and diplococcal-like encapsulated cells in the microscope fields of view, as well as high virulence for susceptible laboratory animals and birds and with a characteristic pronounced property of microbial antagonism.

Short homology-directed repair using optimized Cas9 in the pathogen Cryptococcus neoformans enables rapid gene deletion and tagging.

Cryptococcus neoformans, the most common cause of fungal meningitis, is a basidiomycete haploid budding yeast with a complete sexual cycle. Genome modification by homologous recombination is feasible using biolistic transformation and long homology arms, but the method is arduous and unreliable. Recently, multiple groups have reported the use of CRISPR-Cas9 as an alternative to biolistics, but long homology arms are still necessary, limiting the utility of this method. Since the S. pyogenes Cas9 derivatives used in prior studies were not optimized for expression in C. neoformans, we designed, synthesized, and tested a fully C. neoformans-optimized (Cno) Cas9. We found that a Cas9 harboring only common C. neoformans codons and a consensus C. neoformans intron together with a TEF1 promoter and terminator and a nuclear localization signal (Cno CAS9 or "CnoCAS9") reliably enabled genome editing in the widely used KN99α C. neoformans strain. Furthermore, editing was accomplished using donors harboring short (50 bp) homology arms attached to marker DNAs produced with synthetic oligonucleotides and PCR amplification. We also demonstrated that prior stable integration of CnoCAS9 further enhances both transformation and homologous recombination efficiency; importantly, this manipulation does not impact virulence in animals. We also implemented a universal tagging module harboring a codon-optimized fluorescent protein (mNeonGreen) and a tandem Calmodulin Binding Peptide-2X FLAG Tag that allows for both localization and purification studies of proteins for which the corresponding genes are modified by short homology-directed recombination. These tools enable short-homology genome engineering in C. neoformans.

Infectivity, virulence, pathogenicity, host-pathogen interactions of SARS and SARS-CoV-2 in experimental animals: a systematic review.

The outbreak of the SARS-CoV-2 in mainland China with subsequent human to human transmission worldwide had taken up the shape of a devastating pandemic. The ability of the virus to infect multiple species other than humans has currently been reported in experimental conditions. Non-human primates, felines, ferrets, rodents and host of other animals could previously be infected in experimental conditions with SARS-CoV and recently with SARS-CoV-2, both virus using Angiotensin-converting-enzyme 2 receptor for cellular entry. The variations in sequence homology of ACE2 receptor across species is identified as one of the factors determining virulence and pathogenicity in animals. The infection in experimental animals with SARS-CoV or SARS-CoV-2 on most occasions are asymptomatic, however, the virus could multiply within the respiratory tract and extra-pulmonary organs in most of the species. Here, we discuss about the pathogenicity, transmission, variations in angiotensin-converting-enzyme 2 receptor-binding across species and host pathogen interactions of SARS and SARS-CoV-2 in laboratory animals used in research.

Inoculation With a Microbe Isolated From the Negev Desert Enhances Corn Growth.

Corn (Zea mays L.) is not only an important food source, but also has numerous uses, including for biofuels, fillers for cosmetics, glues, and so on. The amount of corn grown in the U.S. has significantly increased since the 1960’s and with it, the demand for synthetic fertilizers and pesticides/fungicides to enhance its production. However, the downside of the continuous use of these products, especially N and P fertilizers, has been an increase in N2O emissions and other greenhouse gases into the atmosphere as well as run-off into waterways that fuel pollution and algal blooms. These approaches to agriculture, especially if exacerbated by climate change, will result in decreased soil health as well as human health. We searched for microbes from arid, native environments that are not being used for agriculture because we reasoned that indigenous microbes from such soils could promote plant growth and help restore degraded soils. Employing cultivation-dependent methods to isolate bacteria from the Negev Desert in Israel, we tested the effects of several microbial isolates on corn in both greenhouse and small field studies. One strain, Dietzia cinnamea 55, originally identified as Planomicrobium chinense, significantly enhanced corn growth over the uninoculated control in both greenhouse and outside garden experiments. We sequenced and analyzed the genome of this bacterial species to elucidate some of the mechanisms whereby D. cinnamea 55 promoted plant growth. In addition, to ensure the biosafety of this previously unknown plant growth promoting bacterial (PGPB) strain as a potential bioinoculant, we tested the survival and growth of Caenorhabditis elegans and Galleria mellonella (two animal virulence tests) as well as plants in response to D. cinnamea 55 inoculation. We also looked for genes for potential virulence determinants as well as for growth promotion.

UPΦphages, a new group of filamentous phages found in several members of Enterobacteriales.

Filamentous phages establish chronic infections in their bacterial hosts, and new phages are secreted by infected bacteria for multiple generations, typically without causing host death. Often, these viruses integrate in their host’s genome by co-opting the host’s XerCD recombinase system. In several cases, these viruses also encode genes that increase bacterial virulence in plants and animals. Here, we describe a new filamentous phage, UPϕ901, which we originally found integrated in a clinical isolate of Escherichia coli from urine. UPϕ901 and closely related phages can be found in published genomes of over 200 other bacteria, including strains of Citrobacter koseri, Salmonella enterica, Yersinia enterocolitica, and Klebsiella pneumoniae. Its closest relatives are consistently found in urine or in the blood and feces of patients with urinary tract infections. More distant relatives can be found in isolates from other environments, including sewage, water, soil, and contaminated food. Each of these phages, which we collectively call ‘UPϕ viruses’, also harbors two or more novel genes of unknown function.

Genomic analyses of Burkholderia cenocepacia reveal multiple species with differential host-adaptation to plants and humans

BackgroundBurkholderia cenocepacia is a human opportunistic pathogen causing devastating symptoms in patients suffering from immunodeficiency and cystic fibrosis. Out of the 303 B. cenocepacia strains with available genomes, the large majority were isolated from a clinical context. However, several isolates originate from other environmental sources ranging from aerosols to plant endosphere. Plants can represent reservoirs for human infections as some pathogens can survive and sometimes proliferate in the rhizosphere. We therefore investigated if B. cenocepacia had the same potential.ResultsWe selected genome sequences from 31 different strains, representative of the diversity of ecological niches of B. cenocepacia, and conducted comparative genomic analyses in the aim of finding specific niche or host-related genetic determinants. Phylogenetic analyses and whole genome average nucleotide identity suggest that strains, registered as B. cenocepacia, belong to at least two different species. Core-genome analyses show that the clade enriched in environmental isolates lacks multiple key virulence factors, which are conserved in the sister clade where most clinical isolates fall, including the highly virulent ET12 lineage. Similarly, several plant associated genes display an opposite distribution between the two clades. Finally, we suggest that B. cenocepacia underwent a host jump from plants/environment to animals, as supported by the phylogenetic analysis. We eventually propose a name for the new species that lacks several genetic traits involved in human virulence.ConclusionRegardless of the method used, our studies resulted in a disunited perspective of the B. cenocepacia species. Strains currently affiliated to this taxon belong to at least two distinct species, one having lost several determining animal virulence factors.

Cooperativity between the 3' untranslated region microRNA binding sites is critical for the virulence of eastern equine encephalitis virus.

Eastern equine encephalitis virus (EEEV), a mosquito-borne RNA virus, is one of the most acutely virulent viruses endemic to the Americas, causing between 30% and 70% mortality in symptomatic human cases. A major factor in the virulence of EEEV is the presence of four binding sites for the hematopoietic cell-specific microRNA, miR-142-3p, in the 3’ untranslated region (3’ UTR) of the virus. Three of the sites are “canonical” with all 7 seed sequence residues complimentary to miR-142-3p while one is “non-canonical” and has a seed sequence mismatch. Interaction of the EEEV genome with miR-142-3p limits virus replication in myeloid cells and suppresses the systemic innate immune response, greatly exacerbating EEEV neurovirulence. The presence of the miRNA binding sequences is also required for efficient EEEV replication in mosquitoes and, therefore, essential for transmission of the virus. In the current studies, we have examined the role of each binding site by point mutagenesis of the seed sequences in all combinations of sites followed by infection of mammalian myeloid cells, mosquito cells and mice. The resulting data indicate that both canonical and non-canonical sites contribute to cell infection and animal virulence, however, surprisingly, all sites are rapidly deleted from EEEV genomes shortly after infection of myeloid cells or mice. Finally, we show that the virulence of a related encephalitis virus, western equine encephalitis virus, is also dependent upon miR-142-3p binding sites.