Oxford Nanopore MinION sequencing enables rapid whole-genome assembly of Rickettsia typhi in a resource-limited setting

<jats:title>Abstract</jats:title><jats:p>The infrastructure challenges and costs of next-generation sequencing have been largely overcome, for many sequencing applications, by Oxford Nanopore Technologies’ portable MinION sequencer. However the question remains open whether MinION-based bacterial whole-genome sequencing (WGS) is by itself sufficient for the accurate assessment of phylogenetic and epidemiological relationships between isolates and whether such tasks can be undertaken in resource-limited settings. To investigate this question, we sequenced the genome of an isolate of <jats:italic>Rickettsia typhi</jats:italic>, an important and neglected cause of fever across much of the tropics and subtropics, for which only three genomic sequences previously existed. We prepared and sequenced libraries on a MinION in Vientiane, Lao PDR using v9.5 chemistry and in parallel we sequenced the same isolate on the Illumina platform in a genomics laboratory in the UK. The MinION sequence reads yielded a single contiguous assembly, in which the addition of Illumina data revealed 226 base-substitution and 5,856 in/del errors. The combined assembly represents the first complete genome sequence of a human <jats:italic>R. typhi</jats:italic> isolate collected in the last 50 years and differed from the genomes of existing strains collected over a 90-year time period at very few sites, and with no re-arrangements. Filtering based on the known error profile of MinION data improved the accuracy of the Nanopore-only assembly. However, the frequency of false-positive errors remained greater than true sequence divergence from recorded sequences. While Nanopore-only sequencing cannot yet recover phylogenetic signal in <jats:italic>R. typhi</jats:italic>, such an approach may be applicable for more diverse organisms.</jats:p>