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Background/ObjectivesUnderstanding the factors underlying the spatio-temporal distribution of infectious diseases provides useful information regarding their prevention and control. Dengue fever spatio-temporal patterns result from complex interactions between the virus, the host, and the vector. These interactions can be influenced by environmental conditions. Our objectives were to analyse dengue fever spatial distribution over New Caledonia during epidemic years, to identify some of the main underlying factors, and to predict the spatial evolution of dengue fever under changing climatic conditions, at the 2100 horizon.MethodsWe used principal component analysis and support vector machines to analyse and model the influence of climate and socio-economic variables on the mean spatial distribution of 24,272 dengue cases reported from 1995 to 2012 in thirty-three communes of New Caledonia. We then modelled and estimated the future evolution of dengue incidence rates using a regional downscaling of future climate projections.ResultsThe spatial distribution of dengue fever cases is highly heterogeneous. The variables most associated with this observed heterogeneity are the mean temperature, the mean number of people per premise, and the mean percentage of unemployed people, a variable highly correlated with people's way of life. Rainfall does not seem to play an important role in the spatial distribution of dengue cases during epidemics. By the end of the 21st century, if temperature increases by approximately 3°C, mean incidence rates during epidemics could double.ConclusionIn New Caledonia, a subtropical insular environment, both temperature and socio-economic conditions are influencing the spatial spread of dengue fever. Extension of this study to other countries worldwide should improve the knowledge about climate influence on dengue burden and about the complex interplay between different factors. This study presents a methodology that can be used as a step by step guide to model dengue spatial heterogeneity in other countries.

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The rate of amplification of abundant PCR products generally declines faster than that of less abundant products in the same tube in the later cycles of PCR. As a consequence, differences in product abundance diminish as the number of PCR cycles increases. Rehybridization of PCR products which may interfere with primer binding or extension can explain this significant feature in late cycles. Rehybridization occurs with a half-time dependent on the reciprocal of the DNA concentration. Thus, if multiple PCR products are amplified in the same tube, reannealing occurs faster for the more abundant PCR products. In RT-PCR using an internal control, this results in a systematic bias against the more abundant of the two PCR products. In RNA fingerprinting by arbitrarily primed PCR (or differentially display of cDNAs), very large or absolute differences in the expression of a transcript between samples are preserved but smaller real differences may be gradually erased as the PCR reaction proceeds. Thus, this 'C o t effect' may systematically cause an underestimate of the true difference in starting template concentrations. However, differences in starting template concentrations will be better preserved in the less abundant PCR products. Furthermore, the slow down in amplification of abundant products will allow these rarer products to become more visible in the fingerprint which may, in turn, allow rarer cDNAs to be sampled more efficiently. In some applications, where the object is to stochiometrically amplify a mixture of nucleic acids, the bias against abundant PCR products can be partly overcome by limiting the number of PCR cycles and, thus, the concentration of the products. In other cases, abundance normalization at later cycles may be useful, such as in the production of normalized libraries.

BackgroundThe Pacific region is an area unique in the world, composed of thousands of islands with differing climates and environments. The spreading and establishment of the mosquito Aedes aegypti in these islands might be linked to human migration. Ae. aegypti is the major vector of arboviruses (dengue, chikungunya and Zika viruses) in the region. The intense circulation of these viruses in the Pacific during the last decade led to an increase of vector control measures by local health authorities. The aim of this study is to analyze the genetic relationships among Ae. aegypti populations in this region.Methodology/Principal FindingWe studied the genetic variability and population genetics of 270 Ae. aegypti, sampled from 9 locations in New Caledonia, Fiji, Tonga and French Polynesia by analyzing nine microsatellites and two mitochondrial DNA regions (CO1 and ND4). Microsatellite markers revealed heterogeneity in the genetic structure between the western, central and eastern Pacific island countries. The microsatellite markers indicate a statistically moderate differentiation (FST = 0.136; P < = 0.001) in relation to island isolation. A high degree of mixed ancestry can be observed in the most important towns (e.g. Noumea, Suva and Papeete) compared with the most isolated islands (e.g. Ouvea and Vaitahu). Phylogenetic analysis indicated that most of samples are related to Asian and American specimens.Conclusions/SignificanceOur results suggest a link between human migrations in the Pacific region and the origin of Ae. aegypti populations. The genetic pattern observed might be linked to the island isolation and to the different environmental conditions or ecosystems.

A set of 26 Trypanosoma brucei stocks from various African countries, previously characterized by multilocus enzyme electrophoresis (MLEE) for 18 polymorphic loci, have been selected to be representative of the three T. brucei classic subspecies. The kinetoplast DNA minicircle variable regions from these stocks have been amplified using the polymerase chain reaction (PCR) technique, and hybridized with the amplified variable regions of three T. brucei reference stocks, previously identified as T. brucei brucei, T. brucei gambiense, and T. brucei rhodesiense, respectively. Both T. b. brucei and T. b. rhodesiense probes hybridized only with their own stocks, but the T. b. gambiense probe 13 ORSTOM fonds Documentaire TABLE 1 Trypanosoma brucei stocks used in the study Stock (World Health organization identification) Host Country Year References* Subspecies identification and referencest

Gram-negative bacteria were isolated from knots induced by Pseudomonas savastanoi in olive trees (Olea europaea L.). A total of nine endophytic bacterial strains were isolated, each from inside a different tree knot. Biochemical characterization indicated that all the strains belong to the family Enterobacteriaceae. Phylogenetic analyses of the 16S rRNA genes of these novel isolates revealed that they formed a homogeneous cluster within Erwinia species. DNA signatures of these isolates were identical to those described for the genus Erwinia. The strains formed a homogeneous group as shown by DNA-DNA hybridization analysis and numerical analysis of phenotypic data, clearly differentiated from all species of Erwinia with validly published names. The data provide strong evidence of the differentiation of these strains from the most closely related species. Therefore, these isolates represent a novel species, for which the name Erwinia toletana sp. nov. is proposed. The isolates are available at CFBP, CECT and ATCC. The G+C content is 52±0?5 mol%. The type strain is CFBP 6631 T (=A37 T =ATCC 700880 T =CECT 5263 T ). Ewing & Fife (1971, 1972 concluded that strains isolated from clinical sources and strains belonging to the Herbicola group of Dye (1969) are the same species and referred to them as the 'Enterobacter agglomerans-Erwinia herbicola' complex. Lelliott & Dickey (1984) defined Erwinia as associated with plants as pathogens, saprophytes or constituents of the epiphytic flora. They considered Erwinia herbicola as yellow and non-pigmented Erwinia-like organisms that exist either on plant surfaces or as secondary organisms in lesions caused by many plant pathogens, as described by Billing & Baker (1963). Gavini et al. (1989) described the new genus Pantoea and the species Pantoea agglomerans, which includes the type strains of Enterobacter agglomerans, Erwinia herbicola and Erwinia milletiae. Later, Erwinia ananatis (synonym Erwinia uredovora) and Erwinia stewartii were transferred to the genus Pantoea (Mergaert et al., 1993). Based on 16S rRNA gene phylogenetic analyses, plant-associated bacteria were reclassified into four genera: Erwinia, Pectobacterium, Brenneria and Pantoea (Hauben et al., 1998). Mergaert et al. (1999) reclassified nonpigmented Erwinia herbicola epiphytic strains isolated from trees as Erwinia billingiae, which clades within the first cluster of Hauben et al. (1998).Samples from diseased olive trees were collected from the Navahermosa and Chozas areas in the Toledo region of central Spain. Strains from knots were isolated according to the method of García de los Ríos (1999) and were grown on King's medium B (KB) and nutrient agar for 48 h at 25 uC. Two colony types were easily distinguishable on both agar media. Pure cultures were established by single colony isolation onto fresh KB agar. The first type was identified as Pseudomonas savastanoi. The second type, which corresponded to large (3-5 mm), mucilaginous, pigmented and non-pigmented colonies, was identified as a member of 3Present a...

Parasitic protozoa of the genus Leishmania are the causative agents of leishmaniasis. Survival and transmission of these parasites in their different hosts require membrane-bound or extracellular factors to interact with and modify their host environments. Over the last decade, several approaches have been applied to study all the extracellular proteins exported by an organism at a particular time or stage in its life cycle and under defined conditions, collectively termed the secretome or the exoproteome. In this review, we focus on emerging data shedding light on the secretion mechanisms involved in the production of the Leishmania exoproteome. We also describe other methodologies currently available that could be used to analyse the Leishmania exoproteome. Understanding the complexity of the Leishmania exoproteome is a key component to elucidating the mechanisms used by these parasites for exporting proteins to the extracellular space during its life cycle. Given the importance of extracellular factors, a detailed knowledge of the Leishmania exoproteome may provide novel targets for rational drug design and/or a source of antigens for vaccine development.