Clinical Characteristics and Outcomes of Invasive Listeria Monocytogenes Infection: A 45-Year Retrospective Study at a US Tertiary Center.

BACKGROUND: Invasive listeriosis remains a leading cause of foodborne infection-related mortality in the United States and is associated with substantial case fatality despite appropriate antimicrobial therapy. Owing to the relative rarity of invasive disease, contemporary data evaluating clinical characteristics, optimal antimicrobial strategies, and predictors of mortality remain limited. METHODS: We conducted a retrospective cohort study of adults with laboratory-confirmed invasive Listeria monocytogenes infection at Mayo Clinic Health System sites from 1980 to 2024. Clinical syndromes were categorized into 4 mutually exclusive categories, namely bloodstream infection, central nervous system infection, pregnancy-associated infection, and other focal infections. The primary outcome was 1-year all-cause mortality. Secondary outcomes included 90-day mortality and residual neurological deficits among patients with neurolisteriosis. RESULTS: Fifty patients were included (median age, 72 years; 56% immunocompromised). The most common clinical presentations were bacteremia (44%) and neurolisteriosis (36%), followed by endovascular infection (12%) and peritonitis (6%). Most patients received a beta-lactam-based regimen, 46% aminopenicillin monotherapy, and 30% received combination therapy with gentamicin. Thirty-day, 90-day, and 1-year mortality were 10%, 12%, and 20%, respectively. Immunocompromised status and intensive care unit admission were associated with an increased risk of 1-year mortality, whereas adjunctive gentamicin therapy was not associated with improved survival. CONCLUSIONS: Invasive listeriosis is associated with substantial morbidity and mortality, particularly among immunocompromised hosts. Host factors and severity of illness at presentation appear to be key drivers of unfavorable outcomes. Larger multicenter studies are needed to define optimal management strategies.