Department of Medicine, Division of Infectious Diseases, Center for Clinical Epidemiology and Biostatistics, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104-6021, USA. ebbing@mail.med.upenn.edu
Of 49 subjects, 21 were colonized with more than one strain of Escherichia coli and 12 subjects had at least one strain present in fewer than 20% of colonies. The ability to accurately characterize E. coli strain diversity is directly related to the number of colonies sampled and the underlying prevalence of the strain.