Marciniak C, Chen D, Stein AC, Semik PE. Prevalence of Clostridium difficile colonization at admission to rehabilitation. Objectives To assess the prevalence of intestinal colonization with Clostridium difficile ( C. difficile) at admission to acute rehabilitation and to identify risk factors associated with colonization. Design Case-control study. Participants Consecutive admissions to 2 rehabilitation units (spinal cord injury, brain injury and stroke). Setting Free-standing acute rehabilitation facility. Interventions Rectal swabs for culture for C. difficile were obtained at admission and cytotoxin assay performed on all culture positive specimens. Rates of colonization with cytotoxic C. difficile were calculated. Charts were reviewed for medical and demographic factors that may have predisposed patients to colonization, and for possible symptoms at the time of admission. Main Outcome Measures Percentage of patients with culture and cytotoxin assay positive for C. difficile. Frequency of specific patient characteristics that could predispose to C. difficile colonization. Results Of admission stool samples, 16.4% tested positive for C. difficile; none of these patients had been identified as colonized before admission. No patients were discordant for C. difficile positivity on culture and presence of a toxigenic strain. No medical or demographic factors were associated with increased risk of colonization, including age ( t 52=−.748, P=.458, not significant [NS]), diarrhea within 24 hours of admission (χ 1 2 test=.001, P=.973 [NS]), or use of oral or intravenous antibiotics at admission (χ 1 2 test=.044, P=.834 [NS]). Conclusions Patients admitted to acute rehabilitation may have an elevated rate of intestinal colonization with C. difficile without having clinical symptoms. No medical or demographic characteristics were found to be predictive of colonization, however, most of the patients admitted had more than 1 factor that may have increased their susceptibility to infection with this organism. Inadvertent transfer of this organism within the rehabilitation setting may occur because asymptomatic colonization is not recognized.