Background: This study investigated the effect and influence of diabetes severity on susceptibility and 30-day mortality of Staphylococcus aureus bacteremia (SAB).

Methods: Nationwide population-based study of individuals with SAB and matched population controls. Diabetes severity was categorized based on International Classification of Diseases codes and the odds ratio (OR) with 95% confidence intervals (CI) of SAB associated with diabetes was estimated by conditional logistic regression analysis. Hazard ratios (HR) were analyzed by Cox proportional regression. Analyses were adjusted for age, sex, comorbidity, hospital contact and diabetes duration.

Results: Of 25,855 SAB cases, 2797 (10.8%) had diabetes and 2913 (11.3%) had diabetes with complications compared to 14,189 (5.5%) and 5499 (2.1%) of 258,547 controls. This corresponded to an increased risk of SAB associated with diabetes without complications (OR 1.83 (95% CI 1.74–1.92)) and of diabetes with complications (OR 3.62 (95% CI 3.43–3.81) compared to no diabetes. The risk of SAB was highest within the first year of diabetes. Diabetes without complications was associated with an increased risk of 30-day mortality (HR 1.62 (95% CI 1.01–2.60)) compared to no diabetes. Diabetes with complications was overall not associated with increased 30-d mortality (HR 1.36 (95% CI 0.84–2.20)) except for individuals with ketoacidosis/coma (HR 2.01 (95% 1.17–3.45)).

Conclusions: Diabetes, particularly, diabetes with complications significantly increased the risk of SAB. In contrast, there was an increased risk of 30-day mortality after SAB for diabetes without complications but not for diabetes with complications overall. Diabetes with ketoacidosis/coma conferred the highest relative risk of 30-day mortality.