Table 1.
Data from pre-intervention LTACHs [21].
Table 2.
Model 3 parameters and assumptions.
Table 3.
Model calibration and results: CPE LTACH pre-intervention.
Fig 1.
Relationships between facility and equilibrium clinical infection incidence with constant importation.
The curve was generated using formulas for Model 4, at values for the surveillance test frequency ranging from 0 to once per week and no pathogen reduction effect of the intervention. Other model parameters were set at the assumed and estimated values described in Section 3.3, fit to data from CPE in LTACHs. The points (circles) represent average surveillance intervals of, from left to right, one week, two weeks, one month, and no surveillance. Facility was calculated using the formula in Section 3.2.4 with no decolonization, and we calculated infections per admission as the product of the mean length of stay, the per capita clinical detection rate, and the equilibrium prevalence of colonized, non-clinically detected patients, assuming a constant importation rates of 0.01% (solid), 0.1% (dashed), 1% (dotted), and 5% (dash-dot).
Table 4.
and threshold estimates for combined surveillance and decolonization intervention.
Fig 2.
Effect of length-of-stay interventions on facility basic reproduction number.
Calculations of the facility reproduction number, , for Model 3 with the following fixed values calibrated to pre-intervention CRE data in long-term acute care hospitals (Table 3): transmission rate
per day, clinical detection rate
per day, colonization clearance rate
per day, and contact precaution effectiveness
. Length of stay was governed by a 4-parameter mixed exponential–gamma distribution, and specific parameters were varied from the baseline values (Table 3) in a direction that decreased the overall mean length of stay from left-to-right in each of the sub-figures, while holding all other parameters constant. Upper-left: both the exponential rate parameter
and the gamma rate parameter
were simultaneously increased by the same factor from their baseline values. Upper-right: the exponential rate parameter
was increased from its baseline value. Lower-left: the gamma rate parameter
was increased from its baseline value. Lower-right: the fraction of patients following the exponential distribution
was decreased from its baseline value.
Fig 3.
Scatterplot of facility basic reproduction number vs. length of stay (LOS) distribution statistics.
Calculations of the facility reproduction number, , for Model 3 with the following fixed values calibrated to pre-intervention CRE data in long-term acute care hospitals (Table 3): transmission rate
per day, clinical detection rate
per day, colonization clearance rate
per day, and contact precaution effectiveness
. The dots represent
results for 1000 sets of values for each of the four parameters governing the mixed exponential–gamma length of stay distribution, drawn from four independent uniform distributions ranging from 60% to 140% of the calibrated values in Table 3. Each subplot displays the same 1000
results, plotted against different statistics of the length of stay distribution for each set of length-of-stay parameters.