Representative PFGE patterns of S. marcescens isolates recovered during the NICU outbreak. The same strain (PFGE type A, lanes 1, 2, 4, and 6) was recovered in 32 isolates from patients and wet nurses. Genetically unrelated PFGE patterns B, D, G, and F are also shown (lanes 3, 5, 7, and 8). Lane 1, sample ID 1; lane 2, sample ID 17; lane 3, sample ID 21; lane 4, sample ID 27; lane 5, sample ID 33; lane 6, sample ID 10A; lane 7, sample ID 35; lane 8, sample ID 37.