Hoosdally, S. | Search bioRxiv

bioRxiv2020

High precision Neisseria gonorrhoeae variant and antimicrobial resistance calling from metagenomic Nanopore sequencing

The rise of antimicrobial resistant Neisseria gonorrhoeae is a significant public health concern. Against this background, rapid culture-independent diagnostics may allow targeted treatment and prevent onward transmission. We have previously shown metagenomic sequencing of urine samples from men with urethral gonorrhoea can recover near-complete N. gonorrhoeae genomes. However, disentangling the N. gonorrhoeae genome from metagenomic samples and robustly identifying antimicrobial resistance determinants from error-prone Nanopore sequencing is a substantial bioinformatics challenge. Here we demonstrate an N. gonorrhoeae diagnostic workflow for analysis of metagenomic sequencing data obtained from clinical samples using R9.4.1 Nanopore sequencing. We compared results from simulated and clinical infections with data from known reference strains and Illumina sequencing of isolates cultured from the same patients. We evaluated three Nanopore variant callers and developed a random forest classifier to filter called SNPs. Clair was the most suitable variant caller after SNP filtering. A minimum depth of 20x reads was required to confidently identify resistant determinants over the entire genome. Our findings show that metagenomic Nanopore sequencing can provide reliable diagnostic information in N. gonorrhoeae infection.

microbiology↗

bioRxiv2019

Optimizing DNA extraction methods for Nanopore sequencing of Neisseria gonorrhoeae direct from urine samples

BackgroundEmpirical gonorrhoea treatment at initial diagnosis reduces onward transmission. However, increasing resistance to multiple antibiotics may necessitate waiting for culture-based diagnostics to select an effective treatment. There is a need for same-day culture-free diagnostics that identify infection and detect antimicrobial resistance.\n\nMethodsWe investigated if Nanopore sequencing can detect sufficient N. gonorrhoeae DNA to reconstruct whole genomes directly from urine samples. We used N. gonorrhoeae spiked urine samples and samples from gonorrhoea infections to determine optimal DNA extraction methods that maximize the amount of N. gonorrhoeae DNA sequenced whilst minimizing contaminating host DNA.\n\nResultsIn simulated infections the Qiagen UCP Pathogen Mini kit provided the highest ratio N. gonorrhoeae to human DNA and the most consistent results. Depletion of human DNA with saponin increased N. gonorrhoeae yields in simulated infections, but decreased yields in clinical samples. In ten urine samples from men with symptomatic urethral gonorrhoea, [≥]87% coverage of an N. gonorrhoeae reference genome was achieved in all samples, with [≥]92% coverage breath at [≥]10-fold depth in 7 (70%) samples. In simulated infections if [≥]104 CFU/ml of N. gonorrhoeae was present, sequencing of the large majority of the genome was frequently achieved. N. gonorrhoeae could also be detected from urine in cobas PCR Media tubes and from urethral swabs, and in the presence of simulated Chlamydia co-infection.\n\nConclusionUsing Nanopore sequencing of urine samples from men with urethral gonorrhoea sufficient data can be obtained to reconstruct whole genomes in the majority of samples without the need for culture.

microbiology↗