There is great concern about infections with methicillin-resistant Staphylococcus aureus (MRSA) in hospitals, their emergence in the community setting, and the spectrum of variants that also are resistant to vancomycin. Understanding the spread of MRSA requires adequate ways of distinguishing the many different strains and this paper introduced a novel, unambiguous way of characterizing Staphylococcus aureus strains.

Multilocus sequence typing (MLST) had recently been introduced as a precise way of characterizing isolates of bacterial pathogens and this paper developed this approach for S. aureus.

We had developed MLST with our collaborators in 1998 and were keen to promote this sequence-based approach to strain characterization to other major bacterial pathogens. Mark Enright in my lab was developing MLST schemes for a number of pathogens and S. aureus was an obvious one—as it causes serious disease—and there was the major concern about MRSA, and of the emergence of strains resistant to vancomycin. We were dismayed by the fact that the methods of characterizing MRSA that were being used did not allow different laboratories to easily compare their strains. People in different countries were giving local names to the MRSA strains causing problems in their hospitals, and it was very unclear which strains were the same, and which were different. We decided to try and sort this out using MLST.

Just as individual humans can be distinguished using fingerprinting, so the many different strains of a typical bacterial pathogen can be distinguished using appropriate methods. Ideally, these methods should be unambiguous and should allow strains characterized in different countries to be compared easily via the internet. The MLST technique we introduced for characterizing the important strains of Staphylococcus aureus—particularly the antibiotic-resistant MRSA strains that cause so many infections in hospitals—allows strains to be characterized unambiguously, which facilitates studies of their spread within and between hospitals, and also internationally.