Effects of various concentrations of colchicine on internalization of L. monocytogenes, S. typhimurium, P. mirabilis, and E. coli by confluent Caco-2 and HT-29 enterocytes. Enterocytes were pretreated for 1 h with either 0, 1, 5, or 25 μg of colchicine per ml, and colchicine was present throughout the subsequent bacterial internalization assay. Horizontal lines indicate lower limit of assay detection.