Immunosuppression, resistance burden, and qSOFA on short-term prognosis and difficult clearance in hospitalized patients with Salmonella infection: a single-center retrospective cohort study

BACKGROUND: Immunosuppressed patients who develop Salmonella infection are more likely to experience bacteremia, sepsis, and treatment failure; however, systematic evidence remains limited regarding how different sources of immunosuppression and resistance burden jointly affect early outcomes. Using a source-based classification of immunosuppression, we evaluated the relationships of host severity (qSOFA), pathogen resistance burden, 30-day composite adverse outcomes, and difficult clearance. METHODS: We retrospectively enrolled 232 hospitalized patients with Salmonella infection between October 2014 and January 2026. Patients were stratified as typhoidal/paratyphoidal Salmonella (TS) or nontyphoidal Salmonella (NTS) according to serotype and grouped by the source of immunosuppression. Infection phenotypes were classified as enteric, bloodstream/sepsis, mixed/multisite, or other focal phenotypes. Independent associated factors were identified using multivariable logistic regression. RESULTS: The incidence of the 30-day composite adverse outcome was 10.8% (25/232), and the incidence of difficult clearance was 22.0% (51/232). Immunosuppressed patients were more likely to present with bloodstream or disseminated infection phenotypes, but immunosuppression itself was not an independent determinant of 30-day adverse outcomes. qSOFA ≥ 2 was independently associated with the 30-day composite adverse outcome among patients with available qSOFA data (aOR 5.36, 95% CI 1.56-15.95, P = 0.006). Typhoidal Salmonella was significantly associated with difficult clearance in the primary model. Higher phenotypic resistance burden showed an association with difficult clearance in the primary analysis, but this association was not robust after the score was reconstructed using only high-coverage antimicrobial agents. CONCLUSIONS: In hospitalized patients with Salmonella infection, infection-phenotype distributions varied across sources of immunosuppression, although this observation was exploratory because of small subgroup sizes. The qSOFA-related prognostic findings primarily apply to adult or adult-skewed patients with available qSOFA data. Phenotypic resistance burden may reflect treatment complexity, but its association with difficult clearance should be interpreted cautiously because it lacked robustness in the high-coverage sensitivity analysis.