Long-term clonal dynamics of sequence type 72 among methicillin-resistant and methicillin-susceptible Staphylococcus...

Long-term clonal dynamics of Staphylococcus aureus remain incompletely characterized, particularly with respect to differences between methicillin-resistant (MRSA) and methicillin-susceptible (MSSA) populations. We analyzed the sequence type (ST) distribution of 800 S. aureus blood isolates collected in Korea between 1999 and 2018 using multilocus sequence typing.

Temporal trends of ST72 were examined separately for MRSA and MSSA isolates and compared using interaction-based modeling and annual percent change (APC) analyses.

The distribution of STs differed between MRSA and MSSA and changed over time. Among MRSA isolates, ST5 remained a predominant lineage throughout the study period. ST72 accounted for 16.9% of all isolates and increased over time in both MRSA and MSSA populations. ST72 emerged earlier and expanded more steadily among MRSA isolates, whereas its appearance among MSSA isolates showed a later onset and greater interannual variability. Although temporal slopes did not differ significantly between populations, APC estimates indicated a steeper increase of ST72 among MSSA isolates.

These findings demonstrate the long-term establishment of ST72 within the Korean S. aureus population and highlight distinct population-level expansion patterns between MRSA and MSSA.