1864. Trends in Staphylococcus aureus Bacteremia Rates among U.S. Acute Care Hospitals, January 2017- June 2021

Background Previous estimates of methicillin-resistant and -sensitive Staphylococcus aureus (MRSA, MSSA) bacteremia rates in hospitalized patients showed decreases in hospital-onset (HO) MRSA, no changes in community-onset (CO) MRSA and HO MSSA, and slight increases in CO MSSA rates from 2012–2017; more recent trends have not been well characterized. Methods We calculated monthly S. aureus bacteremia rates using microbiology data from hospitals reporting antibiotic susceptibility results in the Premier Healthcare Database from January 2017- June 2021. S. aureus blood isolates resistant to methicillin, oxacillin, or cefoxitin were categorized as MRSA. Positive blood cultures collected on or before hospital day 3 were categorized as CO; those collected on day 4 or later were categorized as HO. Annual rate differences were assessed using generalized estimating equation models with a negative binomial distribution adjusting for hospital bed size, teaching status, urban/rural designation, discharge month, census division, distributions of patient age, sex and race and hospital-level clustering. Results Among 11 million discharges from 356 hospitals, we identified 5,627 HO S. aureus bacteremia events: 2,558 (45%) MRSA and 3,069 (55%) MSSA. In 2017, we observed HO MRSA bacteremia rates of 0.41 and HO MSSA rates of 0.49 per 10,000 patient-days. Compared with 2017, adjusted rates of HO MRSA and MSSA bacteremia were significantly higher in 2019, 2020, and 2021 (Figure 1). Of 42,587 CO S. aureus bacteremia events, 19,107 (45%) were MRSA and 23,480 (55%) MSSA. CO MRSA bacteremia rates were lowest in 2017 (1.52 per 1,000 discharges), and adjusted rates were significantly higher in all later years (Figure 2); we observed significant regional variability in annual differences (p=0.018). The observed CO MSSA bacteremia rate was 2.03 per 1,000 discharges in 2017, and adjusted rates were significantly higher in 2020 and 2021. Figure 1.Hospital-Onset MRSA and MSSA Bacteremia Incidence Rate Ratios* with 95% confidence intervals, 2017 – 2021**.*Reference year =2017.**2021 includes data during January – June.***Statistically significant at p Conclusion In contrast with previous trends, recent S. aureus bacteremia rates in this cohort have increased in comparison to 2017. Potential explanations warranting exploration include differences in regional trends and pandemic-associated changes in inpatient risk, severity of illness, length of stay, and hospital utilization Disclosures All Authors: No reported disclosures.