Salmonella enterica pulsed-field gel electrophoresis clusters, Minnesota, USA, 2001-2007

We determined characteristics of Salmonella entericapulsed-fi eld gel electrophoresis clusters that predict their being solved (i.e., that result in identifi cation of a confirmed outbreak). Clusters were investigated by the Minnesota Department of Health by using a dynamic iterative model. During 2001-2007, a total of 43 (12.5%) of 344 clusters weresolved. Clusters of >4 isolates were more likely to be solved than clusters of 2 isolates. Clusters in which the first 3 case isolates were received at the Minnesota Department of Health within 7 days were more likely to be solved than were clusters in which the first 3 case isolates were received over a period >14 days. If resources do not permit investigation of all S. enterica pulsed-field gel electrophoresis clusters, investigationof clusters of >4 cases and clusters in which the first 3 case isolates were received at a public health laboratory within 7 days may improve outbreak investigations.