What is MLST?
With the use of nucleotide sequencing it is possible to perform a
fine-scale typing of microbial variants which can greatly improve
our understanding of bacterial species, genera, populations,
ecosystems and epidemiology.
In order to compare experiments it is required that DNA sequencing and analysis is performed using a portable standard. One such standard is multilocus sequence typing (MLST) which was first proposed by Maiden et al. [Maiden et al., 1998]. Currently, MLST is used to type isolates of bacterial and fungal species for epidemiological and evolutionary studies. For some recent reviews of MLST technology and its applications, see [Taylor and Fisher, 2003,Urwin and Maiden, 2003,Sullivan et al., 2005,Maiden, 2006].
Briefly described, an MLST scheme for a given organism defines a number of internal fragments to be sequenced. These fragments have a length of approximately 450- to 500-bp and are usually chosen to lie in well conserved regions such as housekeeping genes to ensure that general primers can be designed for PCR amplification and sequencing of all species members.
For each fragment, the scheme also contains a dynamic list of the different known alleles. Each allele is assigned a number and by using this numbering system each new isolate can be assigned a complete allelic profile based on all the defined fragments. Each distinct allelic profile in the scheme is called a sequence type (ST) and given a unique number.