Staphylococcus aureus colonization increases the risk of bacteremia in hemodialysis patients: a molecular epidemiology approach with time-dependent analysis

Background: Bacteremia is the second cause of death in hemodialysis patients and colonization may be a risk factor. We analyzed the association between Staphylococcus aureus or multidrug-resistant Gram-negative bacteria colonization and bacteremia in hemodialysis patients. Methods: A prospective cohort study was conducted. Colonization status was determined at baseline, 2, and 6 months later. The time-to-first-bacteremia was analyzed using the baseline status and time-dependent nature of colonization. The recurrence of bacteremia given colonization status was evaluated using a Poisson regression model. The genetic relatedness between isolates that colonized and caused bacteremia were established by molecular typing methods. Results: Seventy-one patients developed bacteremia over the course of follow-up, with the majority of cases being caused by S aureus (n = 28; 39.4%) and only three caused by multidrug-resistant Gram-negative bacteria. S aureus colonization was associated with an increased risk of bacteremia in time-dependent analysis (HR:4.64; 95%CI: 1.72-12.53) and with recurrence of infection in Poisson model (IRR:5.90, 95%CI: 2.29-15.16). Molecular methods revealed that 77.8% of patients with S aureus bacteremia were colonized with the same strain that caused the infection. Conclusions: S aureus is a cause of endogenous infection in hemodialysis patients. Colonization is associated with both time-to-first-bacteremia and the recurrence of infection. The prompt identification of colonized patients and the evaluation of decolonization protocols are needed.