Multilocus sequence typing: A new method and the first results in the genotyping of bacteria

Comparative characterization (molecular typing) of isolates within a bacter ial species is one of the major problems in microbiology and epidemiology. However, it is rather difficult to correlate data obtained in various labor atories, because traditional, including molecular, methods employed in typi ng pathogenic micro-organisms are difficult to standardize. In 1998, Maiden et al. proposed multilocus sequence typing (MLST); through which alleles o f several housekeeping genes are directly assessed by nucleotide sequencing , each unique allele combination determining a sequence type of a strain. T he advantages of this approach are that the culturing of pathogenic microor ganisms could be excluded, as their gene fragments are amplified directly f rom biological samples, and that the sequencing data are unambiguous, easy to standardize, and electronically portable. The latter makes it possible t o generate an expandable global database for each species at an Internet si te in order to use it for the purposes of genotyping pathogenic bacteria (a nd other infectious agents). MLST protocols have been elaborated for Neisse ria meningitidis, Streptococcus pneumoniae, and Helicobacter pylori; those for Streptococcus pyogenes, Staphylococcus aureus, and Haemophilus influenz ae are now being developed. Basic principles and the first results of MLST have been reviewed, including data on the distribution and microevolution o f N. meningitidis clones causing epidemic meningococcal infection, the rela tive recombination and mutation rates in the N. meningitidis genome, the id entification of antibiotic-resistant S. pneumoniae clones causing severe sy stemic infection, the grouping of H. pylori isolates from various geographi c regions, etc.