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F Renaud

Publications and source records attributed to F Renaud.

At least 19 recordsLinked to original sources
PubMed2006

Molecular divergences of the Ornithodoros sonrai soft tick species, a vector of human relapsing fever in West Africa.

The soft tick Ornithodoros sonrai is recognized as the only vector of Borrelia crocidurae causing human relapsing fever in West Africa. Its determination has been exclusively based on morphological features, geographical distribution and vector competence. Some ambiguities persist in its systematics and may cause misunderstanding about West African human relapsing fevers epidemiology. By amplifying and aligning 16S and 18S rDNA genes in O. sonrai specimens collected from 14 distinct sites in Senegal and Mauritania, we showed the existence of four genetically different subgroups that were morphologically and ecologically identified as belonging to the same species. Within O. sonrai, intraspecific polymorphism was high (pairwise divergence from 0.2% to 16.4%). In all cases, these four subgroups formed a monophyletic clade sharing a common ancestor with East African soft ticks that transmit Borrelia duttoni human relapsing fever. From amplification of the flagellin gene of B. crocidurae we verified that all subgroups of O. sonrai were infected by B. crocidurae and may constitute vectors for this pathogen. All flagellin sequences were identical, refuting the hypothesis suggesting parallel evolution between O. sonrai and B. crocidurae. However, differences in infection rates were significant, suggesting different vector competences between subgroups of O. sonrai.

Africa, Western↗
PubMed2006

[Bacterial adhesion to intraocular lenses and endophthalmitis prevention: review of the literature].

Bacterial adhesion to intraocular lenses (IOLs) during their implantation is a major etiological factor of postoperative endophthalmitis. Polypropylene was the first biomaterial that allowed this relation of cause and effect between bacterial adhesion and endophthalmitis to be proven. Adhesion to IOLs has been investigated in several in vitro studies, with contradictory results reported, due to variations in experimental conditions: the incubation times and the methods all varied. Adhesion is affected by the type of IOL, the bacterial strains, and the surrounding medium. Since this medium is very difficult to model because of its complexity, in vivo studies seemed essential. We have recently determined in vivo progression in the amount of adhering Staphylococcus epidermidis to five types of IOLs. There have been few epidemiological studies published to determine the relationship between endophthalmitis and the IOL type. However, the perfect biomaterial that could prevent postoperative endophthalmitis does not yet exist. Globally, hydrophilic materials and hydrophobic acrylic seem to be less sticky than silicone or PMMA, but this remains to be proven clinically.

Bacterial Adhesion↗
PubMed2005

"Clonal" population structure of the malaria agent Plasmodium falciparum in high-infection regions.

The population genetic structure of Plasmodium falciparum, the agent of malignant malaria, has been shown to be predominantly "clonal" (i.e., highly inbred) in regions of low infectivity; in high-infectivity regions, it is often thought to be panmictic, or nearly so, although there is little supporting evidence for this. The matter can be settled by investigating the parasite's genetic makeup in the midgut oocysts of the mosquito vector, where the products of meiosis can directly be observed. The developmental stages of P. falciparum are haploid, except in the oocysts of infected mosquito vectors, where two gametes fuse, diploidy occurs, and meiosis ensues. We have investigated genetic polymorphisms at seven microsatellite loci located on five chromosomes by assaying 613 oocysts in 145 mosquitoes sampled from 11 localities of Kenya, where malignant malaria is perennial and intense. There is considerable allelic variation, 16.3 +/- 2.1 alleles per locus, and considerable inbreeding, approximately 50% on the average. The inbreeding is caused by selfing (approximately 25%) and nonrandom genotype distribution of oocysts among mosquito guts (35%). The observed frequency of heterozygotes is 0.43 +/- 0.03; the expected frequency, assuming random mating, is 0.80 +/- 0.05. Linkage disequilibrium is statistically significant for all 21 pairwise comparisons between loci, even though 19 comparisons are between loci in different chromosomes, which is consistent with strong deviation from panmixia and the consequent reproduction of genomes as clones, without recombination between gene loci. This is of considerable evolutionary significance and of epidemiological consequence, concerning the spread of multilocus drug and vaccine resistance.

Animals↗
PubMed2004

Meager genetic variability of the human malaria agent Plasmodium vivax.

Malaria is a major human parasitic disease caused by four species of Plasmodium protozoa. Plasmodium vivax, the most widespread, affects millions of people across Africa, Asia, the Middle East, and Central and South America. We have studied the genetic variability of 13 microsatellite loci in 108 samples from 8 localities in Asia, Africa, South America, and New Guinea. Only one locus is polymorphic; nine are completely monomorphic, and the remaining three are monomorphic in all but one or two populations, which have a rare second allele. In contrast, Plasmodium falciparum displays extensive microsatellite polymorphism within and among populations. We further have analyzed, in 96 samples from the same 8 localities, 8 tandem repeats (TRs) located on a 100-kb contiguous chromosome segment described as highly polymorphic. Each locus exhibits 2-10 alleles in the whole sample but little intrapopulation polymorphism (1-5 alleles with a prevailing allele in most cases). Eight microsatellite loci monomorphic in P. vivax are polymorphic in three of five Plasmodium species related to P. vivax (two to seven individuals sampled). Plasmodium simium, a parasite of New World monkeys, is genetically indistinguishable from P. vivax. At 13 microsatellite loci and at 7 of the 8 TRs, both species share the same (or most common) allele. Scarce microsatellite polymorphism may reflect selective sweeps or population bottlenecks in recent evolutionary history of P. vivax; the differential variability of the TRs may reflect selective processes acting on particular regions of the genome. We infer that the world expansion of P. vivax as a human parasite occurred recently, perhaps <10,000 years ago.

Animals↗
PubMed2004

Evolutionary relationships between 15 Plasmodium species from new and old world primates (including humans): an 18S rDNA cladistic analysis.

We present a new phylogenetic analysis of 15 primate Plasmodium species based on 18S rDNA sequences including new sequences of Plasmodium coatneyi, P. fieldi, P. gonderi, P. hylobati and P. simium. The results are discussed in the context of the parasite host species and their geographical distribution. Contrary to other phylogenies constructed with this 18S rDNA molecule, we observed that the topology of phylogenetic trees was not affected either by the quality of the nucleotide matrices, or by the species present in the outgroup. This analysis showed the following. (1) The polyphyly of human Plasmodium is confirmed. (2) The monophyly of Plasmodium from Old World monkeys is confirmed by the new added sequences and P. gonderi, an African species, possibly could be at the root of this group. (3) The most parsimonious biogeographical hypothesis is that P. vivax originated in Asia; thus, its related species P. simium appears to be derived through a transfer from the human P. vivax to New World monkey species in South America. (4) Sampling efforts of non-human primate Plasmodium could permit improvement of the knowledge of primate Plasmodium phylogeny and also consideration of the risks of malaria emergence from monkey reservoirs.

Animals↗
PubMed2004

Field and experimental evidence of preferential selfing in the freshwater mollusc Lymnaea truncatula (Gastropoda, Pulmonata).

We have conducted a thorough study of the mating system of Lymnaea truncatula, the intermediate host of the liver fluke, using three approaches: (i) a population genetics study, (ii) controlled pairings in the laboratory and (iii) a progeny-array analysis. The population genetics study revealed high levels of inbreeding in the studied populations, with strong clues that the extensive heterozygote deficiencies observed are due to selfing. However, Wahlund effects may also arise due to recolonisations from different source populations after bottleneck events. A breeding experiment helped to disentangle the mating system and the Wahlund effects, and showed that high levels of selfing occurred in isolation and in controlled pairings. However, the progeny-array analysis performed after a high-density culturing of the snails suggests that substantial outcrossing may also occur.

Animals↗
PubMed2004

Small effective population sizes in a widespread selfing species, Lymnaea truncatula (Gastropoda: Pulmonata).

We present here a spatial and temporal population genetic survey of a common freshwater snail, also a predominantly selfing species, Lymnaea truncatula. The rate of genetic diversity loss was quantified by estimating the effective size (Ne) of the snail populations, using two different methods. A temporal survey allowed estimation of a variance effective size of the populations, and a spatial survey allowed the estimation of an inbreeding effective size, from two-locus identity disequilibria estimates. Both methods were consistent and provided low Ne values. Drift due to (i) high amounts of selfing and (ii) fluctuations in population sizes because of temporary habitats, and also selection coupled to genome-wide linkage disequilibria, could explain such reductions in Ne. The loss of genetic diversity appears to be counterbalanced only very partially by low apparent rates of gene flow.

Analysis of Variance↗
PubMed2004

Human birthweight evolution across contrasting environments.

We explore from both theoretical and empirical perspectives the hypothesis that a significant part of the worldwide variability in human birthweight results from adaptive responses to local selective pressures. We first developed an agent-based model to simulate the process of evolutionary selection on life history strategy, and then we performed a comparative analysis across 89 countries worldwide. The model illustrates that optimal birthweight depends on which fitness-reducing risk locally predominates (somatic diseases, parasitic diseases or adverse environmental conditions). When fitness variations between individuals mainly result from somatic diseases (e.g. industrialized countries), or conversely from infectious and parasitic diseases (e.g. developing countries), selection is expected to favour individuals producing larger children. Conversely, when environmental risks increase in relative importance, selective pressures for producing children with high birthweight are reduced. The comparative analysis supports these theoretical expectations, in particular the finding that birthweight is higher than predicted in highly parasitized countries.

Adaptation, Physiological↗
PubMed2003

Significant linkage disequilibrium and high genetic diversity in a population of Plasmodium falciparum from an area (Republic of the Congo) highly endemic for malaria.

A study based on 28 microsatellite loci was performed on 32 isolates of Plasmodium falciparum from Pointe Noire (Republic of the Congo) and compared with a cosmopolitan sample of 21 isolates collected from different countries in Africa, Latin America, and Asia. The Pointe Noire population exhibited very high genetic diversity (A = 7.8 +/- 2.6, He = 0.79 +/- 0.11). Significant linkage disequilibria were observed in 28 of 378 pairs of microsatellite loci. This result could be explained by two non-exclusive hypotheses: 1) uniparental propagation (i.e., selfing), leading to non-panmictic associations, and/or 2) a Wahlund effect (i.e., spatial population genetic heterogeneity). These observations are in agreement with data previously obtained from isozyme loci of the same isolates, but contrast with other population genetic analyses conducted in other hyperendemic zones.

Alleles↗
PubMed2003

Evolutionary implications of a high selfing rate in the freshwater snail Lymnaea truncatula.

Self-compatible hermaphroditic organisms that mix self-fertilization and outcrossing are of great interest for investigating the evolution of mating systems. We investigate the evolution of selfing in Lymnaea truncatula, a self-compatible hermaphroditic freshwater snail. We first analyze the consequences of selfing in terms of genetic variability within and among populations and then investigate how these consequences along with the species ecology (harshness of the habitat and parasitism) might govern the evolution of selfing. Snails from 13 localities (classified as temporary or permanent depending on their water availability) were sampled in western Switzerland and genotyped for seven microsatellite loci. F(IS) (estimated on adults) and progeny array analyses (on hatchlings) provided similar selfing rate estimates of 80%. Populations presented a low polymorphism and were highly differentiated (F(ST) = 0.58). Although the reproductive assurance hypothesis would predict higher selfing rate in temporary populations, no difference in selfing level was observed between temporary and permanent populations. However, allelic richness and gene diversity declined in temporary habitats, presumably reflecting drift. Infection levels varied but were not simply related to either estimated population selfing rate or to differences in heterozygosity. These findings and the similar selfing rates estimated for hatchlings and adults suggest that within-population inbreeding depression is low in L. truncatula.

Alleles↗
PubMed2002

Occurrence of a sibling species complex within neotropical lymnaeids, snail intermediate hosts of fascioliasis.

The delimitation of cryptic species within the genus Lymnaea, which are the main vectors of fascioliasis, remains a topic of controversy. An analysis of genetic variability based on 12 enzyme loci revealed different fixed alleles at 9 loci between two sympatric samples of Lymnaea viatrix at the type locality in Lima, Peru. The absence of heterozygotes within this locality indicates the presence of isolated populations or cryptic species within L. viatrix. Significant genetic differences were also found between these two L. viatrix samples from Lima and other populations of L. viatrix in South America and in addition to species such as L. truncatula, L. cubensis and L. columella. Moreover, the lack of variability within each Lymnaea samples studied indicates the existence of a high selfing rate in each species.

Animals↗
PubMed2002

Genetic structure of Candida glabrata populations in AIDS and non-AIDS patients.

The genotypes of 63 strains (11 reference strains and 52 strains from hospitalized patients) of the haploid yeast Candida glabrata were determined from 33 putative gene enzymatic loci. This enabled the characterization of 26 different multilocus genotypes. Genetic differentiation was found between distant hospitals (located in Montpellier and Paris, France) but not for other parameters (anatomic origins or human immunodeficiency virus-positive [HIV+] and HIV- patients). Strong nonrandom association between loci could be seen. Such statistical linkages were confirmed upon comparing the patterns of 14 RAPD [random(ly) amplified polymorphic DNA] primers from 20 of these strains to results obtained from multilocus enzyme electrophoresis analysis. This finding suggests a mainly clonal mode of reproduction of C. glabrata. The consequences of the clonality displayed by C. glabrata populations on the epidemiology of this yeast are also discussed.

AIDS-Related Opportunistic Infections↗
PubMed2002

Negative influence of Gammarinema gammari (Nematoda) on the fecundity of Microphallus papillorobustus (Trematoda): field and experimental evidence.

The gammarid amphipod Gammarus insensibilis frequently harbors adult individuals of the ectoparasitic nematode Gammarinema gammari as well as metacercariae of the trematode Microphallus papillorobostus. After the demonstration in a previous study of a negative relationship between the abundance of these 2 parasites, the nature of the relationship between these 2 parasites was explored in more detail by studying, in the field and in the laboratory, the influence of nematode abundance on trematode fecundity. In gammarids collected in the field, a negative relationship between metacercarial fecundity and the number of co-occurring nematodes was found. By manipulating the nematode abundance in the laboratory, it was confirmed that G. gammari has a negative effect on egg production in M. papillorobustus.

Animals↗
PubMed2001

Morphological and genetic differentiation of Rodentolepis straminea (Goeze, 1752) and Rodentolepis microstoma (Dujardin, 1845) (Hymenolepididae).

The two related species, Rodentolepis straminea (Goeze, 1782) and Rodentolepis microstoma (Dujardin, 1845) (Cestoda, Hymenolepididae), both parasites of rodents, were compared morphologically and electrophoretically. Adult worms were isolated from three wild rodent species of the family Muridae (Apodemus flavicollis, Apodemus sylvaticus, and Mus musculus) from three different sites in Spain and France. Although these two species were strikingly similar in morphological appearance, some of the morphological and metrical features analysed (scolex, mature segments and eggs) can be used for differentiation. Fixed allelic differences were found. Of the ten enzymes detected by starch-gel electrophoresis, six (AAT, AK, GPI, MDH, NP, PGM) showed characteristic isoenzyme profiles in each species. Only in MPI, PEPC, PEPD, and ME enzyme loci were no differences found. The study revealed that the two taxa can be clearly differentiated.

Alleles↗
PubMed2001

A longitudinal study of lung transplant recipients infected with Aspergillus: genetic polymorphism of A fumigatus.

BACKGROUND: Aspergillus infection is a well-known complication of lung transplantation and remains associated with high mortality rates. Molecular typing methods are required to elucidate the complex epidemiology of Aspergillus disease in lung transplant recipients. METHODS: Eight lung transplant recipients from one hospital were followed for A fumigatus colonization or infection. Forty-four sequential isolates from these patients were selected and typed by three molecular methods (random amplified polymorphic DNA, sequence-specific DNA primer and multi-locus enzyme electrophoresis). RESULTS: Sixteen different types were identified of which 14 were specific to 1 patient. A factorial correspondence analysis showed that variability between sequential isolates from a single patient was as high as between isolates from the other patients. Lung transplant recipients presented many different genotypes, reflecting the environmental diversity of A fumigatus. Nevertheless, throughout their follow-up, 2 of the 8 lung transplant recipients harbored a common genotype that was not replaced by others. CONCLUSIONS: These results confirm the important genetic polymorphism of the A fumigatus population. The observed genotypes were not related to the type of Aspergillus disease or anti-fungal treatment used nor to the outcome of the patient. These data confirm that all A fumigatus molecular types present the same pathogenic risk.

Adult↗