Whole genome sequencing of an unusual serotype of Shiga toxin-producing Escherichia coli.

Shiga toxin-producing Escherichia coli serotype O117:K1:H7 is a cause of persistent diarrhea in travelers to tropical locations. Whole genome sequencing identified genetic mechanisms involved in the pathoadaptive phenotype. Sequencing also identified toxin and putative adherence genes flanked by sequences indicating horizontal gene transfer from Shigella dysenteriae and Salmonella spp., respectively.

Combined genomarkers approach to Salmonella characterization reveals that nucleotide sequence differences in the phase 1 flagellin gene fliC are markers for variation within serotypes.

The characterization and tracking of pathogenic micro-organisms in the clinical laboratory and public health environment demand schemes that are easy to standardize and use, are automated and high-throughput, and provide portable data. A combined genomarkers approach for Salmonella enterica based on comparative sequence analysis by mass spectrometry has been developed. The scheme targets genes encoding synthesis and assembly of antigens, metabolic pathway enzymes, virulence factors and fluoroquinolone resistance, covering the essential sequences that distinguish between and identify variation within serotypes. This study demonstrated how this single method could replace the combination of methods currently required to determine serotypes, subtypes, antibiotic resistance profiles and the genomic relatedness of Salmonella isolates. The results revealed genomic variation within seven serotypes previously unreported. This variation can be detected by using nucleotide sequence differences in the Salmonella flagellin gene fliC as markers that are not detected by traditional serotyping methods.

IS6110-based global phylogeny of Mycobacterium tuberculosis.

IS6110, a Mycobacterium tuberculosis complex species-specific insertion element, is targeted primarily for DNA fingerprinting of M. tuberculosis strains. The number and chromosomal positions of copies of this element have been found to be highly variable between unrelated strains and have been exploited for molecular epidemiological purpose but the utility of IS6110 as an informative marker of strain phylogeny has yet to be demonstrated. In the current study, a recently proposed IS6110-targetting PCR based typing methodology, fluorescent amplified fragment length polymorphism (fAFLP) was applied to a global panel of 166 of the clinically more predominant 'modern' strains characterised by spoligotype and, where available, Variable Number Tandem Repeat (VNTR) to identify potentially evolutionarily informative common fragments that could define strains as belonging to established genetic lineages. These common fragments are hereby proposed to be ancestral insertion sites present in common ancestors of these strains rather than preferential insertion sites or 'hot spots'. Results indicate that the exact same spoligotype and VNTR-defined lineages are reflected in the fragment patterns but with greater resolution and are able to clearly define the very distinct Haarlem, LAM, X and also the currently ill-defined T and S and lineages and spoligotypes designated as U, or unknown, without ambiguity. The biogeographical patterns generated reflect the migration of mankind across the globe and indicate that only four successful clones (or individual bacteria) gave rise to virtually all of the tuberculosis in Europe and the Americas. Potential lies in the application of the data to determine IS6110 evolutionary events that have occurred during the evolution of these lineages.