Comparative genomics of a drug-resistant Pseudomonas aeruginosa panel and the challenges of antimicrobial resistance prediction from genomes.

Antimicrobial resistance (AMR) is now recognized as a global threat to human health. The accessibility of microbial whole-genome sequencing offers an invaluable opportunity for resistance surveillance via the resistome, i.e. the genes and mutations underlying AMR. Unfortunately, AMR prediction from genomic data remains extremely challenging, especially for species with a large pan-genome. One such organism, for which multidrug-resistant (MDR) isolates are frequently encountered in the clinic, is Pseudomonas aeruginosa. This study focuses on a commercially available panel of seven MDR P. aeruginosa strains. The main goals were to sequence and compare these strains' genomes, attempt to predict AMR from whole genomes using two different methods and determine whether this panel could be an informative complement to the international P. aeruginosa reference panel. As expected, the results highlight the complexity of associating genotype and AMR phenotype in P. aeruginosa, mainly due to the intricate regulation of resistance mechanisms. Our results also urge caution in the interpretation of predicted resistomes regarding the occurrence of gene identity discrepancies between strains. We envision that, in addition to accounting for the genomic diversity of P. aeruginosa, future development of predictive tools will need to incorporate a transcriptomic, proteomic and/or metabolomic component.

BAC library construction, screening and clone sequencing of lake whitefish (Coregonus clupeaformis, Salmonidae) towards the elucidation of adaptive species divergence.

Genomic DNA sequences and other genomic resources are essential towards the elucidation of the genomic bases of adaptive divergence and reproductive isolation. Here, we describe the construction, characterization and screening of a nonarrayed BAC library for lake whitefish (Coregonus clupeaformis). We then show how the combined use of BAC library screening and next-generation sequencing can lead to efficient full-length assembly of candidate genes. The lake whitefish BAC library consists of 181,050 clones derived from a single heterozygous fish. The mean insert size is 92 Kb, representing 5.2 haploid genome equivalents. Ten BAC clones were isolated following a quantitative real-time PCR screening approach that targeted five previously identified candidate genes. Sequencing of these clones on a 454 GS FLX system yielded 178,000 reads with a mean length of 358 bp, for a total of 63.8 Mb. De novo assembly and annotation then allowed retrieval of contigs corresponding to each candidate gene, which also contained up- and/or downstream noncoding sequences. These results suggest that the lake whitefish BAC library combined with next-generation sequencing technologies will be key resources to achieve a better understanding of both adaptive divergence and reproductive isolation in lake whitefish species pairs as well as salmonid evolution in general.