Odilorhabdins, Antibacterial Agents that Cause Miscoding by Binding at a New Ribosomal Site.

Growing resistance of pathogenic bacteria and shortage of antibiotic discovery platforms challenge the use of antibiotics in the clinic. This threat calls for exploration of unconventional sources of antibiotics and identification of inhibitors able to eradicate resistant bacteria. Here we describe a different class of antibiotics, odilorhabdins (ODLs), produced by the enzymes of the non-ribosomal peptide synthetase gene cluster of the nematode-symbiotic bacterium Xenorhabdus nematophila. ODLs show activity against Gram-positive and Gram-negative pathogens, including carbapenem-resistant Enterobacteriaceae, and can eradicate infections in animal models. We demonstrate that the bactericidal ODLs interfere with protein synthesis. Genetic and structural analyses reveal that ODLs bind to the small ribosomal subunit at a site not exploited by current antibiotics. ODLs induce miscoding and promote hungry codon readthrough, amino acid misincorporation, and premature stop codon bypass. We propose that ODLs' miscoding activity reflects their ability to increase the affinity of non-cognate aminoacyl-tRNAs to the ribosome.

Circumsporozoite protein rates, blood-feeding pattern and frequency of knockdown resistance mutations in Anopheles spp. in two ecological zones of Mauritania.

BACKGROUND: Mosquitoes belonging to Anopheles gambiae species complex are the main malaria vector in Mauritania but data on their vector capacities, feeding habits and insecticide susceptibility are still scanty. The objectives of this study were to fill this gap. METHODS: Adult Anopheles spp. mosquitoes were collected using pyrethrum spray catch method from two ecological zones of Mauritania: Nouakchott (Saharan zone) and Hodh Elgharbi region (Sahelian zone). Circumsporozoite proteins (CSP) for P. falciparum, P. vivax VK210 and P. vivax VK247 were detected by enzyme-linked immunosorbent assay (ELISA) from the female anopheline mosquitoes. To confirm CSP-ELISA results, polymerase chain reaction (PCR) was also performed. Blood meal identification was performed in all engorged females by partial sequencing of the mitochondrial cytochrome b gene. Molecular assessments of pyrethroid knockdown resistance (kdr) and insensitive acetylcholinesterase resistance (ace-1) were conducted. RESULTS: In Nouakchott, the only species of Anopheles identified during the survey was Anopheles arabiensis (356 specimens). In Hodh Elgharbi, 1016 specimens of Anopheles were collected, including 578 (56.9%) Anopheles rufipes, 410 (40.35%) An. arabiensis, 20 (1.96%) An. gambiae, 5 (0.5%) An. pharoensis and 3 (0.3 %) An. funestus. Three of 186 female An. arabiensis collected in Nouakchott and tested by ELISA were found positive for Plasmodium vivax VK210, corresponding to a sporozoite rate of 1.6%; however PCR confirmed infection by P. vivax sporozoite in only one of these. In Hodh Elgharbi, no mosquito was found positive for Plasmodium spp. infection. There was a statistically significant difference in the percentage of human blood-fed Anopheles spp. between Nouakchott (58.7%, 47 of 80 blood-engorged An. arabiensis females) and Hodh Elgharbi (11.1%, 2 of 18 blood-engorged mosquitoes). Analysis of the kdr polymorphisms showed 48.2% (70/145) of East African kdr mutation (L1014S) in Nouakchott compared to 10% (4/40) in Hodh Elgharbi region (P < 0.001). Nevertheless, West African kdr mutation (L1014F) was found only in An. gambiae populations (4/40, 10%) from Hodh Elgharbi region. No ace-1 mutation was found in mosquito specimens from the two study zones. CONCLUSIONS: Overall, this study confirmed the autochthonous P. vivax malaria transmission in Nouakchott, involving An. arabiensis as the main vector. It also described for the first time the absence of ace-1 mutation, the co-occurrence of both West and East African kdr mutation in An. gambiae in Mauritania, and highlighted the regional variations in the prevalence and type of kdr mutations.

A rapid and specific real time RT-PCR assay for diagnosis of Toscana virus infection.

BACKGROUND: To scan a virus (TOSV) belongs to the Phlebovirus genus within the Bunyaviridae family. TOSV is an arbovirus transmitted by sandflies. In Mediterranean countries, TOSV is one of the major viral pathogens involved in aseptic meningitis and meningoencephalitis. OBJECTIVES: Development and assessment of a new sensitive and specific real-time RT-PCR assay for TOSV diagnosis. STUDY DESIGN: TOSV-specific primers and probe targeting the S-segment of the genome were designed, based on recent TOSV sequences available in public databases. Sensitivity was assessed using 10-fold serial dilutions of a RNA transcript and serial dilutions of TOSV strains isolated from infected human beings. Specificity was determined by testing RNA extracts from closely related Phleboviruses. The assay was then used for TOSV infection diagnosis in 971 clinical samples and for TOSV detection in 2000 sandflies. RESULTS: The real-time RT-PCR assay exhibited a sensitivity of under 257 copies per reaction for the RNA transcripts and 0.0056 and 0.014 TCID50 of Italian and Spanish TOSV genotypes per reaction, respectively. No other close Phleboviruses were detected. TOSV was identified in 17 clinical samples and in 3 sandflies. CONCLUSIONS: The assay described is a rapid, robust and reliable real-time RT-PCR test for accurate diagnosis of human TOSV infection as well as for the surveillance of TOSV in vector populations.

A new challenge for hospitals in southeast France: monitoring local populations of Aedes albopictus to prevent nosocomial transmission of dengue or chikungunya.

Aedes albopictus was first identified in southern France in 2004, inducing an emerging risk for autochthonous transmission around imported cases of dengue or chikungunya, and also for mosquito-borne nosocomial transmission in hospitals. Aedes albopictus has been present in Marseille since September 2009 and in Aix-en-Provence since August 2010. Because of the possible admission of viremic patients with dengue or chikungunya in the hospitals of these cities, a mosquito survey was conducted in 2011 in 2 of the hospitals, with the use of mosquito traps. Aedes albopictus was detected with Eisenhans II traps and egg traps in both hospitals during the warm season.