Drug resistance and vaccine target surveillance of Plasmodium falciparum using nanopore sequencing in Ghana.

Malaria results in over 600,000 deaths annually, with the highest burden of deaths in young children living in sub-Saharan Africa. Molecular surveillance can provide important information for malaria control policies, including detection of antimalarial drug resistance. However, genome sequencing capacity in malaria-endemic countries is limited. We designed and implemented an end-to-end workflow to detect Plasmodium falciparum antimalarial resistance markers and diversity in the vaccine target circumsporozoite protein (csp) using nanopore sequencing in Ghana. We analysed 196 clinical samples and showed that our method is rapid, robust, accurate and straightforward to implement. Importantly, our method could be applied to dried blood spot samples, which are readily collected in endemic settings. We report that P. falciparum parasites in Ghana are mostly susceptible to chloroquine, with persistent sulfadoxine-pyrimethamine resistance and no evidence of artemisinin resistance. Multiple single nucleotide polymorphisms were identified in csp, but their significance is uncertain. Our study demonstrates the feasibility of nanopore sequencing for malaria genomic surveillance in endemic countries.

Volatile organic compounds of Metarhizium brunneum influence the efficacy of entomopathogenic nematodes in insect control.

The entomopathogenic fungus (EPF) Metarhizium brunneum occupies the same ecological niche as entomopathogenic nematodes (EPN), with both competing for insects as a food source in the rhizosphere. Interactions between these biocontrol agents can be antagonistic or synergistic. To better understand these interactions, this study focussed on investigating the effect of M. brunneum volatile organic compounds (VOCs), 1-octen-3-ol and 3-octanone, on EPN survival and behaviour. These VOCs proved to be highly toxic to the infective juveniles (IJs) of the EPN Steinernema carpocapsae, Steinernema feltiae and Heterorhabditis bacteriophora with mortality being dose dependent. Chemotaxis studies of H. bacteriophora IJs in Pluronic F127 gel revealed significant preference for the VOCs compared with controls for all tested concentrations. The VOCs also impacted on the test insects in a dose-dependent manner with 3-octanone being more toxic to Galleria mellonella, Cydia splendana and Curculio elephas larvae than 1-octen-3-ol. Mortality of C. splendana and G. mellonella larvae was significantly higher when exposed to relatively high doses (>25%) of 3-octanone. Lower doses of 3-octanone and 1-octen-3-ol immobilised test insects, which recovered after exposure to fresh air for 2 hrs. In depth studies on H. bacteriophora showed that exposure of IJs to > 10% concentration of 3-octanone or 1-octen-3-ol negatively affected infectivity whereas exposure to lower doses (0.1%, 0.01%) had no effect. The VOCs affected IJs, reducing penetration efficacy and the number of generations inside G. mellonella but they failed to inhibit the bacterial symbiont, Photorhabdus kayaii. The ecological significance of VOCs and how they could influence EPF-EPN insect interactions is discussed.