Multistate modelling used for the excess length of stay analysis.

Patients enter the model in state 1 at hospital admission, make a transition into state 2 at the time of infection (whether ESBL-positive or ESBL-negative BSI) then move to the absorbing state 3 at the time of discharge or death. Patients who do not experience an infection during their hospital stay move directly from state 1 to state 3. BSI: Bloodstream infection. ESBL-positive: Enterobacteriaceae producing extended spectrum beta-lactamase. ESBL-negative: Enterobacteriaceae susceptible to beta-lactams.