Molecular characteristics and clinical features of Staphylococcus epidermidis healthcare-associated late-onset bacteremia among infants hospitalized in neonatal intensive care units

Background: Though Staphylococcus epidermidis was the most common pathogen of late-onset sepsis (LOS) in neonatal intensive care units (NICUs), there haves been scanty reports on molecular epidemiology of S. epidermidis isolates from infants stayed in NICU and on correlation of molecular characteristics with clinical features in these infants. Methods: We collected and characterized S. epidermidis bloodstream isolates from infants hospitalized in NICU of a medical center in Taiwan between 2018 and 2020. Medical records of these infants were retrospectively reviewed. Results: A total of 107 isolates identified from 78 episodes of bacteremia in 75 infants were included for analysis. Of the 78 isolates (episodes), 24 pulsotypes, 11 sequence types (STs), and 5 types of staphylococcal chromosomal cassette (type I–V) were identified. ST59 and its single locus variant ST1124 (37.2%) comprised the most common strain, followed by ST35 (14.1%), ST2 (11.5%), and ST89 (10.3%). All but 5 isolates (73/78, 93.6%) belonged to clonal complex (CC) 2. Comparing infants infected with genetically different strains, the patients with underlying immune disease were significantly associated with ST2 infection (P = 0.021), while no statistically significant differences were found in terms of clinical and laboratory characteristics. Only 3.8% of the isolates were susceptible to oxacillin. Conclusions: More than 90% of S. epidermidis bloodstream isolates from infants in NICU in Taiwan were resistant to oxacillin. Though diverse, more than 90% of the isolates (episodes) belonged to CC2. No statistically significant differences were found in terms of clinical characteristics among the infants infected with genetically different strains.