830 - The effect of a long-stay patient on transmission of a pathogen to shorter-stay patients in a small multi-bed hospital unit: Implications for infection control

Background:

Objective: To quantify the effect of a long-stay patient in a hospital unit on the likelihood of colonization of that patient and other patients in the unit.

Prolonged hospital and intensive care unit (ICU) stays have been found to be risk factors for colonization and infection with bacteria such as carbapenem-resistant Enterobacteriaceae (CRE) for which there are limited treatment options and high mortality rates, making prevention of transmission and infection important public health objectives. Many studies have shown that long-stay patients (such as inpatient rehabilitation or skilled nursing facility patients) are at higher risk for hospital-acquired infections than short-stay patients, but the impact of long-stay patients on other patients in the same hospital unit has not received as much attention. Here, we consider a mathematical model of pathogen transmission within a hospital unit and assess the impact at different patient-patient transmission rates of a single long-stay patient on the probability that any other patient leaves the unit colonized with a pathogen.

Methods: We estimated the increased risk caused by a colonized long-stay patient on colonization of other patients using an ordinary differential equation Markov model with three mechanisms of colonization (pre-existing colonization, environmental transmission, and patient-patient transmission) with parameters previously estimated from a 13-bed hospital rehabilitation unit to evaluate the probability of exiting colonized.

Results: A single colonized long-stay patient increases the probability of each other patient exiting the unit colonized from 10.4% to 17.3%, a relative increase in risk of 1.4, and increases the expected number of colonized patients within the unit from 1.37 to 2.07 (not including the long-stay colonized patient).Probability of exiting colonized from a unit with a long-stay, initially colonized patient versus the probability of exiting colonized from a unit with no long-stay patient. The solid black line indicates a unit with regular turnover, whereas the dashed black line indicates a unit with a single long-stay, initially colonized patient. The vertical line shows the value of γ = 0.002 inferred from data from a 13-bed rehabilitation unit, and the shaded regime indicates the uncertainty in this estimate (0.000329, 0.003729).


Conclusion: Colonized long-stay patients pose a risk to other uncolonized patients in the unit, especially at higher patient-patient transmission rates. Potential long-stay patients should be screened for CRE at entry and periodically during their stay because they are both at higher risk of colonization and also of transmitting bacteria to other patients. Consider increased surveillance, isolation, and/or decolonization of long-stay patients.