A Longitudinal Study of Adult Patients with Staphylococcus aureus Bacteremia over 11 Years in Korea

Background: The temporal changes in the Staphylococcus aureus genotypes causing S. aureus bacteremia (SAB) and the corresponding clinical changes over the last decade in South Korea are rarely investigated. Methods: A longitudinal study of adult SAB patients was conducted in a large referral hospital in Seoul, South Korea. Adult monomicrobial SAB patients were enrolled between August 2008 and December 2018. Genotyping was performed by multilocus sequence typing (MLST) and staphylococcal protein A (spa) typing. Trends in changes were identified by linear regression analysis. Results: Of 1782 adult SAB patients, the blood isolates of 1,778 (99.8%) and 1,634 (91.7%) were determined to be MLST and spa type, respectively. ST5 (-2.626%/year) and ST239 (-0.354%/year) decreased during the study period (P < 0.001 for both), but ST72 (2.009%/yr)-and ST8 (0.567%/yr) increased (P < 0.001 for both). The most common genotype was changed from ST5 in 2008 (44.9%) to ST72 in 2018 (36.3%). Panton-Valentine leukocidin-positive spa- t008-MRSA (USA300) was found in 28.6%. Central venous catheter (CVC)-related SAB (-2.440%/yr) and persistent SAB (-1.016%/yr) decreased, but mortality and recurrence rates were unchanged. Conclusion: Over the last decade, the hospital clones ST5 and ST239 have been replaced by community genotype ST72. This was associated with decreased CVC-related and persistent SAB. Increased USA300 was observed in community and hospital settings. Further research is required to identify the reasons for the ST72 epidemic and predict the impending epidemic of ST8 strains, including USA300.