Multilocus Sequence Typing: An Adaptable Tool for Understanding the Global Epidemiology of Bacterial Pathogens

Multilocus sequence typing (MLST) compares internal DNA sequences in multiple, selectively neutral housekeeping genes around the chromosome. When MLST is applied to many pathogens, founding sequence types (STs) appear to emerge and subsequently diverge to form clonal complexes (CCs) composed of closely related STs. However, what actually often emerge and disseminate in time and space are highly adapted virulence gene sequence types (VTs) or epidemic clones (ECs), which do not diverge, probably due to strong negative selective pressure. CCs likely correlate with VTs due to a hitchhiking effect, but VTs (ECs) and not CCs are what disseminate and cause epidemics. Integrating novel multilocus subtyping strategies with the increasing number of whole genome sequences will lead to a deeper understanding of the long-term and short-term epidemiology of pathogens. Such an approach will also allow the creation of a real-time, global epidemiology network to rapidly track and control epidemics around the world.