Bacteremia in the Republic of Korea

In 2015, and were proposed as new species, distinct from and collectively referred to as the complex. However, no clinical reports of these new species exist in Korea. Upon the application of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) for all bloodstream isolates since September 2022, was identified in one patient. Therefore, we aimed to search for new species among the archives of the bacteremia cohort and describe their clinical and microbiological characteristics. Among the 691 archived isolates between 2012 and 2018, one was identified as via MALDI-TOF MS. Both isolates (one in 2022) were obtained from patients with extensive pneumonia accompanied by bacteremia and both cases had fatal outcomes. They harbored multiple virulence genes ( and ) but did not harbor and . No matched sequence type (ST) was found in either isolate, and both isolates were closely related to ST1594, ST1593, ST1793, and ST1303, which belonged to accounted for <1% of the complex but had clinical characteristics similar to . Therefore, clinicians should be aware of these factors to avoid misidentifying these strains as coagulase-negative staphylococci, and appropriate reporting is required to minimize confusion.IMPORTANCE, a member of complex, has been reported as an important pathogen that causes clinically invasive infections in humans similar to . Clinical isolates of have been reported across the world, showing a large geographical difference in prevalence and genomic profile. However, there have been no clinical reports regarding this new species in Korea. This is the first report to investigate the clinical and genetic characteristics of identified in patients with bacteremia, and the proportion of bacteremia among bacteremia cohort in Korea.