Forty Years of Erratic Insecticide Resistance Evolution in the Mosquito Culex pipiens

One view of adaptation is that it proceeds by the slow and steady accumulation of beneficial mutations with small effects. It is difficult to test this model, since in most cases the genetic basis of adaptation can only be studied a posteriori with traits that have evolved for a long period of time through an unknown sequence of steps. In this paper, we show how ace-1, a gene involved in resistance to organophosphorous insecticide in the mosquito Culex pipiens, has evolved during 40 years of an insecticide control program. Initially, a major resistance allele with strong deleterious side effects spread through the population. Later, a duplication combining a susceptible and a resistance ace-1 allele began to spread but did not replace the original resistance allele, as it is sublethal when homozygous. Last, a second duplication, (also sublethal when homozygous) began to spread because heterozygotes for the two duplications do not exhibit deleterious pleiotropic effects. Double overdominance now maintains these four alleles across treated and nontreated areas. Thus, ace-1 evolution does not proceed via the steady accumulation of beneficial mutations. Instead, resistance evolution has been an erratic combination of mutation, positive selection, and the rearrangement of existing variation leading to complex genetic architecture

Evidence of Introgression of the ace-1R Mutation and of the ace-1 Duplication in West African Anopheles gambiae s. s

Background: The role of inter-specific hybridisation is of particular importance in mosquito disease vectors for predicting the evolution of insecticide resistance. Two molecular forms of Anopheles gambiae s.s., currently recognized as S and M taxa, are considered to be incipient sibling species. Hybrid scarcity in the field was suggested that differentiation of M and S taxa is maintained by limited or absent gene flow. However, recent studies have revealed shared polymorphisms within the M and S forms, and a better understanding of the occurrence of gene flow is needed. One such shared polymorphism is the G119S mutation in the ace-1 gene (which is responsible for insecticide resistance); this mutation has been described in both the M and S forms of A. gambiae s.s. Methods and Results: To establish whether the G119S mutation has arisen independently in each form or by genetic introgression, we analysed coding and non-coding sequences of ace-1 alleles in M and S mosquitoes from representative field populations. Our data revealed many polymorphic sites shared by S and M forms, but no diversity was associated with the G119S mutation. These results indicate that the G119S mutation was a unique event and that genetic introgression explains the observed distribution of the G119S mutation within the two forms. However, it was impossible to determine from our data whether the mutation occurred first in the S form or in the M form. Unexpectedly, sequence analysis of some resistant individuals revealed a duplication of the ace-1 gene that was observed in both A. gambiae s.s. M and S forms. Again, the distribution of this duplication in the two forms most likely occurred through introgression. Conclusions: These results highlight the need for more research to understand the forces driving the evolution of insecticide resistance in malaria vectors and to regularly monitor resistance in mosquito populations of Africa

Overview of the current use of levosimendan in France: a prospective observational cohort study

Abstract Background Following the results of randomized controlled trials on levosimendan, French health authorities requested an update of the current use and side-effects of this medication on a national scale. Method The France-LEVO registry was a prospective observational cohort study reflecting the indications, dosing regimens, and side-effects of levosimendan, as well as patient outcomes over a year. Results The patients included ( n = 602) represented 29.6% of the national yearly use of levosimendan in France. They were treated for cardiogenic shock ( n = 250, 41.5%), decompensated heart failure ( n = 127, 21.1%), cardiac surgery-related low cardiac output prophylaxis and/or treatment ( n = 86, 14.3%), and weaning from veno-arterial extracorporeal membrane oxygenation ( n = 82, 13.6%). They received 0.18 ± 0.07 µg/kg/min levosimendan over 26 ± 8 h. An initial bolus was administered in 45 patients (7.5%), 103 (17.1%) received repeated infusions, and 461 (76.6%) received inotropes and or vasoactive agents concomitantly. Hypotension was reported in 218 patients (36.2%), atrial fibrillation in 85 (14.1%), and serious adverse events in 17 (2.8%). 136 patients (22.6%) died in hospital, and 26 (4.3%) during the 90-day follow-up. Conclusions We observed that levosimendan was used in accordance with recent recommendations by French physicians. Hypotension and atrial fibrillation remained the most frequent side-effects, while serious adverse event potentially attributable to levosimendan were infrequent. The results suggest that this medication was safe and potentially associated with some benefit in the population studied

Mise au point d une préparation en série de collyres renforcés

La kératite bactérienne nécessite un traitement d'urgence par des collyres antibiotiques renforcés (ceftazidime et vancomycine sont couramment associés). La disponibilité de ce type de collyre préparé de façon extemporanée par une pharmacie hospitalière est problématique. Notre objectif est de mettre en place et de valider une fabrication en série conforme aux Bonnes Pratiques de Préparations afin de limiter les contraintes organisationnelles. Tout d'abord, nous avons validé la préparation de collyres à la ceftazidime. Après préparation en salle blanche, les collyres ont été stockés à-20C pendant 84 jours. Des contrôles physico-chimiques, pharmacologiques et bactériologiques ont été réalisés durant cette période. Des collyres renforcés à la ceftazidime à 20 mg/ml dans du chlorure de sodium 0,9% ont un pH et une osmolarité acceptables pour la tolérance oculaire. A J84 de congélation, nous n'avons pas constaté de diminution significative des concentrations en ceftazidime, ni d'augmentation de son principal produit de dégradation, la pyridine. Cette étude souligne que la fabrication en série de collyres renforcés congelés au congélateur est possible et nous amènera à étendre ce travail à d'autres collyres antimicrobiensROUEN-BU Médecine-Pharmacie (765402102) / SudocSudocFranceF

Une nouvelle méthode de spectroscopie IRTF pour l'étude de site de fixation métallique au sein des portéines

Communication oral

Fitness costs and benefits in response to artificial artesunate selection in Plasmodium

International audienceDrug resistance is a major issue in the control of malaria. Mutations linked to drug resistance often target key metabolic pathways and are therefore expected to be associated with biological costs. The spread of drug resistance depends on the balance between the benefits that these mutations provide in the drug-treated host and the costs they incur in the untreated host. The latter may therefore be expressed both in the vertebrate host and in the vector. Research on the costs of drug resistance focusses on interactions with vertebrate host, yet whether they are also expressed in the vector has been overlooked. In this study, we aim to identify the costs and benefits of resistance against artesunate (AS), one of the main artemisinin derivatives used in malaria-endemic countries. For this purpose, we compared different AS-selected lines of the avian malaria parasite Plasmodium relictum to their ancestral (unselected) counterpart. We tested their within host dynamics and virulence both in the vertebrate host and in its natural vector, the mosquito Culex quinquefasciatus. The within-host dynamics of the AS-selected lines in the treated birds was consistent with the phenotype of resistance described in human P. falciparum malaria: a clearance delay during the treatment followed by a recrudescence once the treatment was interrupted. In the absence of treatment, however, we found no significant costs of resistance in the bird. The results of the two experiments to establish the infectivity of the lines to mosquitoes point towards a decreased infectivity of the drugselected lines as compared to the ancestral, reference one. We discuss the potential implication of these results on the spread of artesunate resistance in the field

A new amino-acid substitution in acetylcholinesterase 1 confers insecticide resistance to Culex pipiens mosquitoes from Cyprus

International audienceIn insects, selection of insecticide-insensitive acetylcholinesterase (AChE) is a very common resistance mechanism. Mosquitoes possess both AChE1 and AChE2 enzymes and insensitivity is conferred by single amino-acid changes located near the active site of the synaptic AChE1. Only two positions have been reported so far to be involved in resistance, suggesting a very high structural constraint of the AChE1 enzyme. In particular, the G119S substitution was selected in several mosquitoes' species and is now largely spread worldwide. Yet, a different type of AChE I insensitivity was described 10 years ago in a Culex pipiens population collected in Cyprus in 1987 and fixed thereafter as the ACE-R strain. We report here the complete amino-acid sequence of the ACE-R AChE I and show that resistance is associated with a single Phe-to-Val substitution of residue 290, which also lines the active site. Comparison of AChEI activities of the recombinant F290V protein and ACE-R mosquito extracts confirmed the causal role of the substitution in insensitivity. Biochemical characteristics of the mutated protein indicated that the resistance level varies with the insecticide used. A molecular diagnosis test was designed to detect this mutation and was used to show that it is still present in Cyprus Island. (c) 2006 Elsevier Ltd. All rights reserved

High Wolbachia density in insecticide-resistant mosquitoes

International audienceWolbachia symbionts are responsible for various alterations in host reproduction. The effects of the host genome on endosymbiont levels have often been suggested, but rarely described. Here, we show that Wolbachia density is strongly modified by the presence of insecticide-resistant genes in the common house mosquito, Culex pipiens. The Wolbachia density was estimated using a real-time quantitative PCR assay. Strains harbouring different genes conferring resistance were more infected than a susceptible strain with the same genetic background. We show that this interaction also operates in natural populations. We propose that mosquitoes may control Wolbachia density less efficiently when they carry an insecticide-resistant gene, i.e. when they suffer from a physiological resistance cost