Dynamic Network Model of Clostridium Difficile Infection to Evaluate Treatment Interventions and Costs

* CNISP (Canadian Nosocomial Infection Surveillance Program) † BC (Provincial Infection Control Network of British Columbia) Objectives: Efforts to model Clostridium difficile infection (CDI) to date have been limited. Most models do not address the contribution of asymptomatic carriers as sources of new infections and are restricted to hospital acquired CDI. We aim to develop a simulation model to examine systematically the dynamic relationship between three major subpopulations of CDI transmission: hospitals, communities, and long-term facilities, and to evaluate treatment effectiveness and costs. Methods: We conducted a systematic investigation to determine the key epidemiological factors influencing CDI transmission according to the three major subpopulations: hospitals, communities, and long-term care facilities. We have developed a stochastic agent-tracking meta-population network model of CDI transmission, and identified parameters that would capture transmission from symptomatic and asymptomatic carriers to uninfected individuals among the subpopulations. Results: We identified eight infection states: susceptible, gastrointestinal exposure, colonized, diseased, deceased, clinically resolved colonized, relapse of CDI, and cleared. Key parameters include; health outcomes of target populations, time horizon, diagnostic characteristics, treatment effectiveness, transmission rates, susceptibility rates, recurrence rates, and costs. In the general population 5% -20% of adults are estimated to be asymptomatic carriers of CDI but up to 80% of the elderly in long-term care facilities are considered to be colonized. Age-specific recurrence rates of CDI are important parameters of the model. Major predictors of recurrences were advanced age and duration of initial hospitalizations. The probability of recurrent CDI increases with the number of recurrences experienced. Recurrences were associated with major increases in hospital LOS and costs. Conclusions: Using a scenario-based approach we are well positioned to compare clinical benefits and costs of current treatment regimens (Metronidazole, Vancomycin, Fidaxomicin) with the potential novel approach of duodenal infusion (fecal transplant).