Contaminated provider hand reservoirs were less likely ( all isolates , odds ratio 0.12 , 95 % confidence interval 0.03-0 .50 , P = 0.004 ; without duplicate events , odds ratio 0.05 , 95 % confidence interval 0.01-0 .49 , P = 0.010 ) than contaminated patient or environmental sites to serve as the reservoir of origin for epidemiologically related transmission events .