FIG. 4.

Subtyping of recurrent L. monocytogenes ETs by PFGE of AscI restriction fragments of genomic DNA. PFGE was performed at 200 V with pulse times ramped from 4 to 40 s over 22 h. The recurrent strains ET 35 (lanes 2 to 4), ET 40 (lanes 6 to 8), and ET 42 (lanes 10 to 12) were isolated from food samples obtained on successive visits to processors B, D (milk), and M (nondairy food), respectively. XbaI restriction fragments of genomic DNA from an E. coli reference strain (G5244) were used as molecular size markers (lanes 1, 5, and 9).