MULTILOCUS SEQUENCE TYPING - A PORTABLE APPROACH TO THE IDENTIFICATION OF CLONES WITHIN POPULATIONS OF PATHOGENIC MICROORGANISMS

Traditional and molecular typing schemes for the characterization of p athogenic microorganisms are poorly portable because they index variat ion that is difficult to compare among laboratories. To overcome these problems, we propose multilocus sequence typing (MLST), which exploit s the unambiguous nature and electronic portability of nucleotide sequ ence data for the characterization of microorganisms, To evaluate MLST , we determined the sequences of approximate to 470-bp fragments from 11 housekeeping genes in a reference set of 107 isolates of Neisseria meningitidis from invasive disease and healthy carriers, For each locu s, alleles were assigned arbitrary numbers and dendrograms were constr ucted from the pairwise differences in multilocus allelic profiles by cluster analysis. The strain associations obtained were consistent wit h clonal groupings previously determined by multilocus enzyme electrop horesis. A subset of six gene fragments was chosen that retained the r esolution and congruence achieved by using all 11 loci, Most isolates from hyper-virulent lineages of serogroups A, B, and C meningococci we re identical for all loci or differed from the majority type at only a single locus, MLST using six loci therefore reliably identified the m ajor meningococcal lineages associated with invasive disease, MLST can be applied to almost all bacterial species and other haploid organism s, including those that are difficult to cultivate. The overwhelming a dvantage of MLST over other molecular typing methods is that sequence data are truly portable between laboratories, permitting one expanding global database per species to be placed on a World-Wide Web site, th us enabling exchange of molecular typing data for global epidemiology via the Internet.