Table 1.
Parameters used in modeling the effect of antibiotic versus nonantibiotic treatment of CDAD on VRE colonization.
| Parameter | Patients | Value |
|---|---|---|
| Np | number of patients in the hospital | 400 |
| ρ | ratio of patients to HCW | 4 |
| λ U− off | CDAD−, uncolonized, off antibiotic: admission rate | 50.1 per day |
| γ U− off | CDAD−, uncolonized, off antibiotic: average length of stay | 5 days |
| λ U− on | CDAD−, uncolonized, on antibiotic: admission rate | 2.505 per day |
| γ U− on | CDAD−, uncolonized, on antibiotic: average length of stay | 14 days |
| λ C− off | CDAD−, colonized, off antibiotic: admission rate | 0.334 per day |
| γ C− off | CDAD−, colonized, off antibiotic: average length of stay | 28 days |
| λ C− on | CDAD−, colonized, on antibiotic: admission rate | 0.501 per day |
| γ C− on | CDAD−, colonized, on antibiotic: average length of stay | 28 days |
| τ U− stop | CDAD−, uncolonized, on antibiotic: stop antibiotic | 15% per day |
| τ U− start | CDAD−, uncolonized, off antibiotic: start antibiotic | 15% per day |
| τ C− stop | CDAD−, colonized, on antibiotic: stop antibiotic | 4% per day |
| τ C− start | CDAD−, colonized, off antibiotic: start antibiotic | 16% per day |
| σ | fraction of CDAD+, on antibiotic: stop antibiotic | 0.5 |
| α U+ on | average number of contacts between uncolonized | 8 per day |
| CDAD− patients on antibiotic and HCW | ||
| α U− on | average number of contacts between uncolonized | 8 per day |
| CDAD+ patients on antibiotic and HCW | ||
| β U+ on | probability of colonization per contact between uncolonized | 0.024 |
| CDAD+ patient on antibiotic and contaminated HCW | ||
| β U− on | probability of colonization per contact between uncolonized | 0.06 |
| CDAD− patient on antibiotic and contaminated HCW | ||
| ω U− on | CDAD−, uncolonized, on antibiotic: transit to CDAD+ | 1.07% per day |
| ω C− on | CDAD−, colonized, on antibiotic: transit to CDAD+ | 1.07% per day |
| δ C+ on | CDAD+, colonized, on antibiotic: transit to CDAD− | 27% per day |
| δ C+ off | CDAD+, colonized, off antibiotic: transit to CDAD− | 27% per day |
| δ U+ on | CDAD+, uncolonized, on antibiotic: transit to CDAD− | 27% per day |
| δ U+ off | CDAD+, uncolonized, off antibiotic: transit to CDAD− | 27% per day |
| σ | fraction of AB patients that transit to CDAD+ and stop AB | 0.0 or 0.5 |
|
| ||
| Parameter | Health care workers | Value |
|
| ||
| α C+ | average number of contacts between HCW and colonized CDAD+ patients | 10 per day |
| α C− | average number of contacts between HCW and colonized CDAD+ patients | 10 per day |
| κ − on | probability of contamination per contact between uncontaminated | 0.4 |
| HCW and colonized CDAD− patient on antibiotic | ||
| κ − off | probability of contamination per contact between uncontaminated | 0.4 |
| HCW and colonized CDAD− patient off antibiotic | ||
| κ + on | probability of contamination per contact between uncontaminated | 0.16 |
| HCW and colonized CDAD+ patient on antibiotic | ||
| κ + off | probability of contamination per contact between uncontaminated | 0.16 |
| HCW and colonized CDAD+ patient off antibiotic | ||
| μ | average duration of HCW contamination | 48 minutes |
| η | hand-washing compliance factor between 0 and 1 | 0.6 |
CDAD = clostridium difficile-associated disease; VRE = vancomycin-resistant enterococci; HCW = health care worker; CDAD+ = clostridium difficile-associated disease positive; CDAD− = clostridium difficile-associated disease negative; AB = antibiotics.