scholarly journals Exposing the Diversity of Multiple Infection Patterns

2016 ◽  
Author(s):  
Mircea T. Sofonea ◽  
Samuel Alizon ◽  
Yannis Michalakis
Keyword(s):  
Large Range ◽  
Natural Populations ◽  
Theoretical Models ◽  
Multiple Infection ◽  
Multiple Infections ◽  
Ecological Interactions ◽  
Chronic Infections ◽  
Empirical Reality ◽  
Evolution Of Virulence ◽  
Host Infection

AbstractNatural populations often have to cope with genetically distinct parasites that can coexist, or not, within the same hosts. Theoretical models addressing the evolution of virulence have considered two within host infection outcomes, namely superinfection and coinfection. The field somehow became limited by this dichotomy that does not correspond to an empirical reality, as other infection patterns, namely sets of within-host infection outcomes, are possible. We indeed formally prove there are 114 different infection patterns for the sole recoverable chronic infections caused by horizontally-transmitted microparasites. We afterwards highlight eight infection patterns using an explicit modelling of within-host dynamics that captures a large range of ecological interactions, five of which have been neglected so far. To clarify the terminology related to multiple infections, we introduce terms describing these new relevant patterns and illustrate them with existing biological systems. This characterisation of infection patterns opens new perspectives for understanding the epidemiology and the evolution of parasites.

scholarly journals Evolution of Virulence in Natural Populations of the Satellite RNA of Cucumber mosaic virus

2000 ◽  
Vol 90 (5) ◽  
pp. 480-485 ◽  
Author(s):  
Fernando Escriu ◽  
Aurora Fraile ◽  
Fernando García-Arenal
Keyword(s):  
Cucumber Mosaic Virus ◽  
Mosaic Virus ◽  
Natural Populations ◽  
Theoretical Models ◽  
Aphid Transmission ◽  
Satellite Rna ◽  
Virulence Analysis ◽  
Trade Offs ◽  
Evolution Of Virulence ◽  
Satellite Rnas

From 1986 to 1992, an epidemic of tomato necrosis caused by Cucumber mosaic virus (CMV) plus CMV satellite RNAs (satRNAs) occurred in eastern Spain. From 1989 onward, the frequency of tomato necrosis di-minshed, and it almost completely disappeared after 1991. Analyses of plants infected with CMV and with CMV satRNA and of the phenotype (necrogenic or nonnecrogenic for tomato) induced by some CMV satRNA variants, showed that the disappearance of tomato necrosis was due to changes in the genetic composition of the satRNA population (i.e., to its evolution toward decreased virulence). Analysis of components of the fitness of satRNA variants, necrogenic or nonnecrogenic for tomato, showed that necrogenic and nonnecrogenic variants did not differ in infectivity or in their accumulation level in tomato and that they represented the same fraction of encapsidated RNA. Other fitness components were positively correlated with the greater virulence of necrogenic variants, in that they were favored in mixed infections with nonnecrogenic variants and were more effectively passed into CMV progeny than were nonnecrogenic variants. On the other hand, necrogenic CMV satRNA variants caused a more pronounced depression in the accumulation of CMV than did nonnecro-genic variants, which could affect the efficiency of aphid transmission. Thus, the evolution of virulence in the CMV satRNA population can be explained by trade-offs between factors that determine virulence and factors that affect transmission, as predicted by theoretical models on the evolution of virulence in parasites.

scholarly journals Pseudomonas aeruginosa PA14 Enhances the Efficacy of Norfloxacin against Staphylococcus aureus Newman Biofilms

2020 ◽  
Vol 202 (18) ◽  
Author(s):  
Giulia Orazi ◽  
Fabrice Jean-Pierre ◽  
George A. O’Toole
Keyword(s):  
Cystic Fibrosis ◽  
Staphylococcus Aureus ◽  
Pseudomonas Aeruginosa ◽  
Antimicrobial Agents ◽  
Respiratory Infections ◽  
Multiple Infection ◽  
Bacterial Biofilms ◽  
Interspecies Interactions ◽  
Chronic Infections ◽  
Content Type

ABSTRACT The thick mucus within the airways of individuals with cystic fibrosis (CF) promotes frequent respiratory infections that are often polymicrobial. Pseudomonas aeruginosa and Staphylococcus aureus are two of the most prevalent pathogens that cause CF pulmonary infections, and both are among the most common etiologic agents of chronic wound infections. Furthermore, the ability of P. aeruginosa and S. aureus to form biofilms promotes the establishment of chronic infections that are often difficult to eradicate using antimicrobial agents. In this study, we found that multiple LasR-regulated exoproducts of P. aeruginosa, including 2-heptyl-4-hydroxyquinoline N-oxide (HQNO), siderophores, phenazines, and rhamnolipids, likely contribute to the ability of P. aeruginosa PA14 to shift S. aureus Newman norfloxacin susceptibility profiles. Here, we observe that exposure to P. aeruginosa exoproducts leads to an increase in intracellular norfloxacin accumulation by S. aureus. We previously showed that P. aeruginosa supernatant dissipates the S. aureus membrane potential, and furthermore, depletion of the S. aureus proton motive force recapitulates the effect of the P. aeruginosa PA14 supernatant on shifting norfloxacin sensitivity profiles of biofilm-grown S. aureus Newman. From these results, we hypothesize that exposure to P. aeruginosa PA14 exoproducts leads to increased uptake of the drug and/or an impaired ability of S. aureus Newman to efflux norfloxacin. Surprisingly, the effect observed here of P. aeruginosa PA14 exoproducts on S. aureus Newman susceptibility to norfloxacin seemed to be specific to these strains and this antibiotic. Our results illustrate that microbially derived products can alter the ability of antimicrobial agents to kill bacterial biofilms. IMPORTANCE Pseudomonas aeruginosa and Staphylococcus aureus are frequently coisolated from multiple infection sites, including the lungs of individuals with cystic fibrosis (CF) and nonhealing diabetic foot ulcers. Coinfection with P. aeruginosa and S. aureus has been shown to produce worse outcomes compared to infection with either organism alone. Furthermore, the ability of these pathogens to form biofilms enables them to cause persistent infection and withstand antimicrobial therapy. In this study, we found that P. aeruginosa-secreted products dramatically increase the ability of the antibiotic norfloxacin to kill S. aureus biofilms. Understanding how interspecies interactions alter the antibiotic susceptibility of bacterial biofilms may inform treatment decisions and inspire the development of new therapeutic strategies.

scholarly journals Parasite variation and the evolution of virulence in a Daphnia-microparasite system

Parasitology ◽  
2007 ◽  
Vol 135 (3) ◽  
pp. 303-308 ◽  
Author(s):  
T. J. LITTLE ◽  
W. CHADWICK ◽  
K. WATT
Keyword(s):  
Genetic Variation ◽  
Rank Order ◽  
Genetic Relationships ◽  
Natural Populations ◽  
Host Genotype ◽  
Relative Growth ◽  
Trade Off ◽  
Relative Growth Rates ◽  
Pasteuria Ramosa ◽  
Evolution Of Virulence

SUMMARYUnderstanding genetic relationships amongst the life-history traits of parasites is crucial for testing hypotheses on the evolution of virulence. This study therefore examined variation between parasite isolates (the bacterium Pasteuria ramosa) from the crustacean Daphnia magna. From a single wild-caught infected host we obtained 2 P. ramosa isolates that differed substantially in the mortality they caused. Surprisingly, the isolate causing higher early mortality was, on average, less successful at establishing infections and had a slower growth rate within hosts. The observation that within-host replication rate was negatively correlated with mortality could violate a central assumption of the trade-off hypothesis for the evolution of virulence, but we discuss a number of caveats which caution against premature rejection of the trade-off hypothesis. We sought to test if the characteristics of these parasite isolates were constant across host genotypes in a second experiment that included 2 Daphnia host clones. The relative growth rates of the two parasite isolates did indeed depend on the host genotype (although the rank order did not change). We suggest that testing evolutionary hypotheses for virulence may require substantial sampling of both host and parasite genetic variation, and discuss how selection for virulence may change with the epidemiological state of natural populations and how this can promote genetic variation for virulence.

scholarly journals Ecological Interactions and the Netflix Problem

2016 ◽  
Author(s):  
Philippe Desjardins-Proulx ◽  
Idaline Laigle ◽  
Timothée Poisot ◽  
Dominique Gravel
Keyword(s):  
Machine Learning ◽  
Supervised Learning ◽  
Random Forests ◽  
Species Interactions ◽  
Similarity Measures ◽  
Theoretical Models ◽  
Machine Learning Techniques ◽  
Nearest Neighbour ◽  
Ecological Interactions ◽  
Learning Techniques

0AbstractSpecies interactions are a key component of ecosystems but we generally have an incomplete picture of who-eats-who in a given community. Different techniques have been devised to predict species interactions using theoretical models or abundances. Here, we explore the K nearest neighbour approach, with a special emphasis on recommendation, along with other machine learning techniques. Recommenders are algorithms developed for companies like Netflix to predict if a customer would like a product given the preferences of similar customers. These machine learning techniques are well-suited to study binary ecological interactions since they focus on positive-only data. We also explore how the K nearest neighbour approach can be used with both positive and negative information, in which case the goal of the algorithm is to fill missing entries from a matrix (imputation). By removing a prey from a predator, we find that recommenders can guess the missing prey around 50% of the times on the first try, with up to 881 possibilities. Traits do not improve significantly the results for the K nearest neighbour, although a simple test with a supervised learning approach (random forests) show we can predict interactions with high accuracy using only three traits per species. This result shows that binary interactions can be predicted without regard to the ecological community given only three variables: body mass and two variables for the species’ phylogeny. These techniques are complementary, as recommenders can predict interactions in the absence of traits, using only information about other species’ interactions, while supervised learning algorithms such as random forests base their predictions on traits only but do not exploit other species’ interactions. Further work should focus on developing custom similarity measures specialized to ecology to improve the KNN algorithms and using richer data to capture indirect relationships between species.

On the role of enemies in divergence and diversification of prey: a review and synthesis

2005 ◽  
Vol 83 (7) ◽  
pp. 894-910 ◽  
Author(s):  
Steven M Vamosi
Keyword(s):  
Visual Cues ◽  
Phenotypic Diversity ◽  
Theoretical Models ◽  
Ecological Interactions ◽  
Closely Related Species ◽  
Diversification Rates ◽  
Extinction Rates ◽  
Phenotypic Divergence ◽  
Experimental Approaches

Understanding the contribution of ecological interactions to the origin and maintenance of diversity is a fundamental challenge for ecologists and evolutionary biologists, and one that is currently receiving a great deal of attention. Natural enemies (e.g., predators, parasites, and herbivores) are ubiquitous in food webs and are predicted to have significant impacts on phenotypic diversity and on speciation, and extinction rates of their prey. Spurred by the development of a theoretical framework beginning in the late 1970s, there is now a growing body of literature that addresses the effects of enemy–prey interactions on the evolution of prey. A number of theoretical models predict that enemies can produce phenotypic divergence between closely related species, even in the absence of interspecific competition for resources. Effects on diversification of prey are more variable, and enemies may either enhance or depress speciation and extinction rates of their prey. Empirical evidences from a number of study systems, notably those involving predators and prey in aquatic environments and interactions between insects and flowering plants, confirm both predictions. There is now considerable evidence for the role of enemies, especially those that are size-selective or use visual cues when identifying suitable prey, on phenotypic divergence of sympatric and allopatric taxa. Enemies may spur diversification rates in certain groups under some circumstances, and hinder diversification rates in other cases. I suggest that further research should focus on the role of enemies in diversification of prey, with significant insights likely to be the product of applying traditional experimental approaches and emerging comparative phylogenetic methods.

scholarly journals The Atmospheres of Extrasolar Super-Earths

2008 ◽  
Vol 4 (S253) ◽  
pp. 263-271 ◽  
Author(s):  
Eliza Miller-Ricci ◽  
Sara Seager ◽  
Dimitar Sasselov
Keyword(s):  
Parameter Space ◽  
Large Range ◽  
Theoretical Models ◽  
Radial Velocities ◽  
Atmospheric Composition ◽  
Transmission Spectra ◽  
Earth Atmosphere ◽  
Atmospheric Escape ◽  
Wide Range

AbstractExtrasolar super-Earths (1-10 M⊕) are likely to exist with a wide range of atmospheres. While a number of these planets have already been discovered through radial velocities and microlensing, it will be the discovery of the firsttransitingsuper-Earths that will open the door to a variety of follow-up observations aimed at characterizing their atmospheres. Super-Earths may fill a large range of parameter space in terms of their atmospheric composition and mass. Specifically, some of these planets may have high enough surface gravities to be able to retain large hydrogen-rich atmosphseres, while others will have lost most of their hydrogen to space over the planet's lifetime, leaving behind an atmosphere more closely resembling that of Earth or Venus. The resulting composition of the super-Earth atmosphere will therefore depend strongly on factors such as atmospheric escape history, outgassing history, and the level of stellar irradiation that it receives. Here we present theoretical models of super-Earth emission and transmission spectra for a variety of possible outcomes of super-Earth atmospheric composition ranging from hydrogen-rich to hydrogen-poor. We focus on how observations can be used to differentiate between the various scenarios and constrain atmospheric composition.

Localization, length and reproduction in single- and multiple-worm infections of Echinostoma revolutum (Trematoda) in the chick

Parasitology ◽  
1981 ◽  
Vol 82 (1) ◽  
pp. 49-53 ◽  
Author(s):  
B. Fried ◽  
D. S. Alenick
Keyword(s):  
Localization Length ◽  
Domestic Chick ◽  
Multiple Infection ◽  
Multiple Infections ◽  
Echinostoma Revolutum ◽  
Length Measurements ◽  
Cross Fertilization

SUMMARYMono-metacercarial infections of Echinostoma revolutum in the domestic chick yielded 14- or 15-day-old worms that produced viable eggs, indicating that this species can self-fertilize under conditions which preclude cross-fertilization. In multiple infection studies, chicks were fed either 5 or 10 cysts and each infected chick contained 2–7 worms at necropsy 14 or 15 days later. Worms from multiple infections were mainly paired or clustered and they tended to locate more posteriorly in the intestine than single worms. Length measurements of single and multiple worms were similar. Both the number of eggs and the percentage of hatched eggs were considerably greater in multiple than in single infections.

Prevalence of Rhabdias africanus and other Endoparasites of Sclerophrys regularis (Anura: Bufonidae) From Ogoni Land, Nigeria

2020 ◽  
Vol 41 (2) ◽  
Author(s):  
C.C Amuzie ◽  
T.M Marcus ◽  
J.F Espínola-Novelo
Keyword(s):  
Niger Delta ◽  
The Other ◽  
Multiple Infection ◽  
Multiple Infections ◽  
Helminth Parasites ◽  
Niger Delta Region ◽  
High Prevalence ◽  
Low Prevalence ◽  
Keywords Lung ◽  
Cosmocerca Ornata

Sclerophrys regularis specimens from Ogoni, Nigeria, were investigated for the prevalence of the lung nematodes, Rhabdiasafricanus. Hosts were collected from two locations, Zor Sogho, Bori and Kaani 1, Khana. High prevalence of R. africanusinfection was observed, 69% in Bori and 100% in Khana. Other helminth parasites recovered from the hosts includedacanthocephalan cystacanths, pentastomids (Raillietiella sp.), trematodes (Diplodiscus fischthalicus and Mesocoeliummonodi) and nematodes (ascaridida larvae, Amplicaecum africanum, Cosmocerca ornata, Oswaldocruzia hoepplii). Coinfectionof C. ornata and R. africanus was very common in both locations, and multiple infection was more prevalent thansingle infection. This is the second report of Diplodiscus fischthalicus from a bufonid in Nigeria, with both occurring in thehumid Niger Delta region, however in low prevalence and intensity. The other parasites have been reported by previousauthors. Research into the environmental factors that enhance transmission of Rhabdias africanus should be investigated. Keywords: Lung nematode parasite, bufonids, co-infection, multiple infections, amphibians, Ogoni

scholarly journals Impaired immune evasion in HIV through intracellular delays and multiple infection of cells

2012 ◽  
Vol 279 (1740) ◽  
pp. 3003-3010 ◽  
Author(s):  
Christian L. Althaus ◽  
Rob J. De Boer
Keyword(s):  
Life Cycle ◽  
Immune Escape ◽  
Multiple Infection ◽  
Multiple Infections ◽  
Wild Type ◽  
Hiv Dynamics ◽  
Rate Of Escape ◽  
Multiple Copies ◽  
Infected Cells ◽  
Eclipse Phase

With its high mutation rate, HIV is capable of escape from recognition, suppression and/or killing by CD8 + cytotoxic T lymphocytes (CTLs). The rate at which escape variants replace each other can give insights into the selective pressure imposed by single CTL clones. We investigate the effects of specific characteristics of the HIV life cycle on the dynamics of immune escape. First, it has been found that cells in HIV-infected patients can carry multiple copies of proviruses. To investigate how this process affects the emergence of immune escape, we develop a mathematical model of HIV dynamics with multiple infections of cells. Increasing the frequency of multiple-infected cells delays the appearance of immune escape variants, slows down the rate at which they replace the wild-type variant and can even prevent escape variants from taking over the quasi-species. Second, we study the effect of the intracellular eclipse phase on the rate of escape and show that escape rates are expected to be slower than previously anticipated. In summary, slow escape rates do not necessarily imply inefficient CTL-mediated killing of HIV-infected cells, but are at least partly a result of the specific characteristics of the viral life cycle.

scholarly journals Why multiple infections favour virulent parasites

2018 ◽  
Author(s):  
Mircea T. Sofonea ◽  
Samuel Alizon ◽  
Yannis Michalakis
Keyword(s):  
Dynamical Systems ◽  
Selection Bias ◽  
Selective Pressure ◽  
Growth Traits ◽  
Natural Host ◽  
Multiple Infection ◽  
Multiple Infections ◽  
Host Interactions ◽  
Host Growth ◽  
Host Mortality

AbstractIt is now a fact that several strains/species (hereafter types) of parasites circulate in natural host populations. Parasite polymorphism can even occur within the same host, where distinct parasite types can interact in various ways. This can affect their transmission and, therefore, their evolution. We still lack general predictions regarding the evolution, in such multiple infection contexts, of virulence – the infection-induced host mortality, essentially because its emanation from within-host growth was often ignored so far. Here, we explicitly investigate within-host interactions, within-host competition outcomes, epidemiological dynamics and evolutionary invasibility using a formalism as general as possible. Focusing on chronic dimorphic infections caused by horizontally-transmitted microparasites, we apply both dynamical systems and probabilistic approaches to this bottom-up sequence of dynamics to explore the evolutionary outcomes. We show that within-host growth traits are under strong selective pressure and when small mutations affect them, most of the surviving mutants are more virulent than their resident. We thus identify a robust and unavoidable selection bias towards higher virulence.

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