Differentiation of bacterial species and strains has been carried out for a long time using phenotypic characteristics, such as biochemical profiling, serotyping and more. However, these characteristics can be highly variable within a given strain, depending on a number of factors (such as temperature, culture conditions, presence or absence of specific nutrients etc.) and so a move to genetic methods such as partial 16S rRNA gene sequencing (which is highly conserved and not subject to the growth conditions at the time) provide superior discrimination. However, greater differentiation between strains can be achieved by looking at multiple locations (genes). Multilocus Sequence Typing (MLST) looks at typically seven highly conserved so called ‘housekeeping’ genes which are critical for cell function. Sequencing fragments of these seven key genes provides potentially billions of profiles and sufficient discrimination to identify thousands of strains within a bacterial species. The fragment sequences are assigned numbers to create a profile using online databases, to give the sequence type e.g. ST123
MLST is being used in different areas, for example to identify strains which have known or suspected virulence factors, and as databases continue to expand it remains a key tool for identifying and tracing bacterial strains that cause food poisoning outbreaks.
Participants will be provided with a tube containing bacterial DNA from a specified organism which requires sequencing to identify the MLST type. Results will be reported as the sequence type (ST) for comparison with the known ST of the DNA provided. The PT will be suitable for conventional PCR of MLST loci followed by sequencing or whole genome sequencing (WGS).