Swimming ability of Cronobacter isolates compared to that of the reference strain S. Typhimurium DT104 13348. The reference strain showed an average swimming activity of 60 mm after 8 h of incubation at 37°C. (a) E657, C. sakazakii serotype O:1, clinical origin; (b) CQ8, C. sakazakii serotype O:4, PIF origin; (c) ATCC BAA-894, C. sakazakii serotype O:1, PIF origin; (d) 206N, C. sakazakii serotype O:2, clinical origin.