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BackgroundTransmission of dengue virus (DENV) from humans to mosquitoes represents a critical component of dengue epidemiology. Examinations of this process have generally been hampered by a lack of methods that adequately represent natural acquisition of DENV by mosquitoes from humans. In this study, we assessed artificial and natural blood feeding methods based on rates of DENV infection and dissemination within mosquitoes for use in a field-based epidemiological cohort study in Iquitos, Peru.Methodology/principal findingsOur study was implemented, stepwise, between 2011 and 2015. Participants who were 5 years and older with 5 or fewer days of fever were enrolled from ongoing clinic- and neighborhood-based studies on dengue in Iquitos. Wild type, laboratory-reared Aedes aegypti were fed directly on febrile individuals or on blood collected from participants that was either untreated or treated with EDTA. Mosquitoes were tested after approximately 14 days of extrinsic incubation for DENV infection and dissemination. A total of 58 participants, with viremias ranging from 1.3 × 10(2) to 2.9 × 10(6) focus-forming units per mL of serum, participated in one or more feeding methods. DENV infection and dissemination rates were not significantly different following direct and indirect-EDTA feeding; however, they were significantly lower for mosquitoes that fed indirectly on blood with no additive. Relative to direct feeding, infection rates showed greater variation following indirect-EDTA than indirect-no additive feeding. Dissemination rates were similar across all feeding methods. No differences were detected in DENV infection or dissemination rates in mosquitoes fed directly on participants with different dengue illness severity.Conclusions/significanceOur study demonstrates the feasibility of using direct and indirect feeding methods for field-based studies on vector competence. Direct mosquito feeding is preferable in terms of logistical ease, biosecurity, and reliability.

Rckettsia asembonensis belongs to a group of R. felis-like organisms (RFLOs) that are similar, yet distinct, from their closest known relative, R felis (1,2). Although R felis causes disease in [...]

Infections with scrub typhus group orientiae (STGO) are a common and widespread cause of fever in Asia, the western Pacific, and northern Australia (the tsutsugamushi triangle). The causative pathogen, Orientia [...]

Despite several reports worldwide documenting the presence of Rickettsia asembonensis in samples derived from ectoparasites, animals and more recently humans, genomic information of these specimens remains scarce, and when available, is usually limited to small genomic fragments of limited value. We generated complete sequences for two conserved (17-kDa antigen gene and gltA ) and three variable ( sca4 , ompB and ompA ) genes in five R. asembonensis DNA samples detected in cat and dog fleas in Peru. Complete gene sequences were used to conduct multi-locus sequence typing and phylogenetic analyses to assess diversity and infer relationships among strains and other reference sequences. The 17-kDa antigen gene was highly conserved across Rickettsia species. Of the variable genes ompB was the most variable, but this diversity was not captured through phylogenetics alone even when efforts were made to maximize potential diversity in terms of flea species, animal host and location. Through a combination of de novo and reference-based genome assembly we identified a 75 bp insertion in ompA that encodes a 25 aa repetitive motif found in other Rickettsia species, but not present in the original prototype strain from Kenya. R. asembonensis has only recently been shown to be a bona-fide human pathogen. As such, and compounded by a lack of available genomic information, it remains understudied. Our work directly addresses the lack of genomic information available worldwide for the study of these novel Rickettsia species and specifically contributes to our understanding of the diversity and molecular epidemiology of R. asembonensis in Peru.

The reported prevalence of vancomycin-resistant Enterococcus faecium (VRE) in Switzerland for the years 2008-2010 has been low at <5%. At the University Hospital Zurich, 17 cases of VRE were detected between 28 December 2009 and 15 February 2010. Nine cases were diagnosed clinically; eight cases were detected by rectal screening. The centre of the outbreak was the cardiac surgery department. Four patients suffered from VRE-infections; four patients died. In order to investigate and contain the outbreak, the following measures were taken: prevalence surveys using weekly rectal screening, environmental screening; selective enrichment culturing; pulsed field gel electrophoresis (PFGE) for clonal typing and polymerase chain reaction-analysis (PCR) for resistance determinants and virulence factors detection. Contact isolation in single rooms and enhanced surface-disinfection methods were implemented. Ward nurses were assigned as link nurses. Regular teaching was carried out aiming to improve hand disinfection among healthcare workers. PFGE revealed two main pulsotypes each including seven patients. Five minor pulsotypes originated from three additional patients and one sample collected from a keyboard. Two of three patients with minor pulsotypes had been treated abroad. PCR-analysis identified vanB resistance-genotypes with exception of one vanA resistance-genotype. The outbreak was associated with environmental contamination and insufficient compliance with hand-hygiene. Enhanced awareness and infection control measures resulted in termination of the VRE outbreak within eight weeks. The complexity of the outbreak with several clones in parallel suggests a higher baseline prevalence of VRE in Switzerland than previous surveillance data indicate.