Use of stochastic epidemic modeling to quantify transmission rates of colonization with methicillin-resistant Staphylococcus aureus in an intensive care unit.
OBJECTIVE
To consider statistical methods for estimating transmission rates for colonization of patients with methicillin-resistant Staphylococcus aureus (MRSA) in an intensive care unit (ICU) from three different sources: background contamination, non-isolated patients, and isolated patients.


METHODS
We developed statistical methods that allowed for the analysis of interval-censored, routine surveillance data and extended the general epidemic model for the flow of patients through the ICU.


RESULTS
Within this ICU, the rate of transmission to susceptible patients from a background source of MRSA (0.0092 case per day; 95% confidence interval [CI95], 0.0062-0.0126) is approximately double the rate of transmission from a non-isolated patient (0.0052 case per day; CI95, 0.0013-0.0096) and six times the rate of transmission from an isolated patient (0.0015 case per day; CI95, 0.0001-0.0043). We used the methodology to investigate whether transmission rates vary with workload.


CONCLUSIONS
Our methodology has general application to infection by and transmission of pathogens in a hospital setting and is appropriate for quantifying the effect of infection control interventions.
Forrester
Marie
M
School of Mathematical Sciences, Queensland University of Technology, Brisbane, Queensland, Australia.
Pettitt
Anthony N
AN
D001509:Bed Occupancy / Q000706:statistics & numerical data; D003428:Cross Infection / Q000453:epidemiology* / Q000382:microbiology; D004196:Disease Outbreaks / Q000706:statistics & numerical data*; D018562:Disease Transmission, Infectious / Q000706:statistics & numerical data; D006801:Humans; D017053:Infection Control / Q000706:statistics & numerical data; D007362:Intensive Care Units / Q000706:statistics & numerical data*; D016106:Methicillin Resistance; D015233:Models, Statistical; D009741:Nursing Staff, Hospital / Q000706:statistics & numerical data; D011793:Queensland / Q000453:epidemiology; D013203:Staphylococcal Infections / Q000453:epidemiology* / Q000382:microbiology / Q000635:transmission; D013211:Staphylococcus aureus / Q000187:drug effects*; D013269:Stochastic Processes; D016526:Workload / Q000706:statistics & numerical data