1991. Cluster of Non-toxigenic Corynebacterium diphtheriae Infective Endocarditis Prompting Epidemiologic Investigation — Seattle, Washington 2020-2023

BACKGROUND: Non-toxigenic Corynebacterium diphtheriae (C. diphtheriae), an aerobic gram-positive bacillus, is often associated with wound infections. However, it can also cause outbreaks and invasive disease including infective endocarditis (IE). After identifying a cluster of C. diphtheriae IE cases, we conducted an epidemiologic investigation to identify additional C. diphtheriae detections within our university-affiliated hospital system from 2020-2023. METHODS: We performed retrospective chart review of any patients with C. diphtheriae detected in a clinical specimen (i.e. wound, blood, sputum) between 9/1/2020 and 4/1/2023. A confirmed case of C. diphtheriae IE was defined as at least two positive monomicrobial blood cultures with vegetation(s) on echocardiogram; probable IE was defined as positive monomicrobial blood cultures with embolic phenomena. We describe demographic and clinical characteristics of all patients with C. diphtheriae detection, including patients with C. diptheriae IE. RESULTS: Between 9/1/2020 to 4/1/2023, 45 patients (median age 44 years, range 23-75 years; 76% male, 64% non-Hispanic White, 80% unstably housed) had ≥ 1 clinical specimen with C. diphtheriae; 5 (11%) patients had confirmed (n=4) or probable (n=1) IE. The largest number of C. diphtheriae detections were in December 2022 (Figure 1). Forty-three patients (96%) reported substance use; 19 (42%) reported history of injection drug use (IDU). C. diphtheriae was detected in 34 (76%) polymicrobial wound cultures, 7 (16%) polymicrobial blood cultures with concomitant Staphylococcal or Streptococcal bacteremia, 5 (11%) blood cultures from C. diphtheriae IE, and one (2%) sputum specimen. The five IE cases (80% male, 60% unstably housed) were diagnosed between 5/2022-3/2023 and had current IDU (60%) or open wounds (40%). Four had embolic phenomena; two received cardiac surgery. Four (80%) patients with IE died: three from IE and one from COVID-19. [Figure: see text] CONCLUSION: A cluster of C. diphtheriae IE cases and rising C. diphtheriae detections in our hospital system raise concern for a local outbreak disproportionately affecting patients who use substances and are unstably housed. Outbreak investigation and prevention efforts (wound care, linkage to care) are critical to prevent additional mortality. DISCLOSURES: H. Nina Kim, MD, MSc, Gilead: Grant/Research Support