Bacteremic vs Nonbacteremic Shigella Infections in the United States Veterans Health Administration, 2000–2024

Background Risk factors for Shigella bacteremia are poorly understood. Growing trends in antimicrobial resistance may make treatment of Shigella bacteremia more difficult. We identified risk factors for Shigella bacteremia among Shigella cases who received care in the US Veterans Health Administration (VHA). Methods We identified adults cared for in VHA with Shigella infection from 2000-2024. Shigella bacteremic vs nonbacteremic infections were compared based on patient demographics, comorbidities, outcomes, Shigella species and antimicrobial resistance. We performed log-binomial regression analysis to estimate association of risk factors with Shigella bacteremia. Results Of a total of 1962 Shigella infections in 1861 unique patients, 34 (1.7%) had confirmed bacteremia when blood cultures were checked. Shigella species among bacteremia cases included 13 (38.2%) S. flexneri and 14 (41.2%) S. sonnei, and 7 (2.6%) Shigella nonspeciated. 1266/1962 (64.5%) isolates were tested for antimicrobial susceptibility. No Shigella bacteremia isolates were multidrug resistant (MDR), however isolates from 3 nonbacteremic cases were. All with Shigella bacteremia were hospitalized, while 1/34 (2.9 %) died within 30 days of infection. Comparing characteristics of patients with Shigella bacteremic vs nonbacteremic infections and adjusting for potential confounders, age >65 years and HIV infection were independent risk factors for Shigella bacteremia (aRR [95% CI] 2.90 (1.46-5.76) and 2.37 (1.11-5.06) respectively). Conclusions Clinicians should be aware that patients who are elderly, and/or have HIV infection are at higher risk for Shigella bacteremia, and that these infections can be severe, requiring hospitalization. At this time, MDR Shigella strains have not been detected among bacteremic patients in VHA.