Prevalence of Bacteremia Due to Streptococcus/Enterococcus Species at an Academic/Community Health System Over a Five Year Period
Authors: Zarbock Christopher , Gascoigne Shannon M , Ferrieri Patricia 
Published: November 2023

Abstract
Timely surveillance of bacteremia is important for identifying emerging pathogens and to implement effective antimicrobial strategies and public health measures. Organisms in the genera Streptococcus and Enterococcus are often the cause of bacteremia and merit particular attention. The objective of this study was to determine the prevalence of bacteremia caused by several clinically significant Streptococcus species (S. pyogenes, S. agalactiae, S. pneumoniae, S. dysgalactiae/equisimilis, the S. anginosus group (S. anginosus, S. constellatus, S. intermedius), and Enterococcus species (E. faecium and E. faecalis) over a 5 year period (2017-2022). Bacteria isolated from blood culture bottles were identified by MALDI-TOF mass spectrometry (VITEK® MS). Data were obtained from a Laboratory Results Repository in Epic Beaker to include these organisms, isolated in blood cultures (BCs), patient gender, patient age, and the collection date. The data were then consolidated to yield one unique organism per patient per episode. The prevalence of organisms as a percent of the total positive BCs for the overall time period and for each year was determined. Species from the Enterococcus genus were the two most prevalent organisms for each year except for 2017. E. faecalis was the most prevalent overall (57.4%, n = 534) and for each year except for 2020. Combining all analyzed organisms, S. agalactiae was the third most prevalent organism for each year except for 2017 when it was the second and 2020-2021 when it was the fourth. However, within the Streptococcus genus alone, S. agalactiae was the most prevalent (27.5%, n = 281). S. pneumoniae, demonstrating seasonality, was the second most prevalent from 2018-2019, however, it was outranked by S. dysgalactiae/equisimilis from 2020-2022 when it was the fourth and by the S. anginosus group in 2017 and 2020-2022. S. pyogenes was the fourth most prevalent organism in 2017 and the third most in 2018; however, it decreased in subsequent years and was surpassed by all other organisms. Stratified by decade of life, patients in their seventh decade of life (60-69 yr) accounted for the most positive BCs for every organism, except for E. faecalis, followed frequently by patients in their sixth (50-59 yr) and eighth (70-79 yr) decades of life. Patients in their first decade of life (0-9 yr) accounted for a preponderance of positive BCs for E. faecalis, S. agalactiae (highest prevalence &lt;7 days of life), and S. pneumoniae. This study highlighted the relative abundance of bacteremia caused by Enterococcus species. Additionally, it demonstrated the importance of Streptococcus agalactiae bacteremia, especially in the first and seventh decades of life. Finally, this study showed the increasing prevalence of organisms within the Streptococcus anginosus group and Streptococcus dysgalactiae/equisimilis. This analysis demonstrated the dynamics of bacteremia and prevalence among several species within the Enteroccocus and Streptococcus genera.