Use of pulsed-field gel electrophoresis to link sporadic cases of invasive listeriosis with recalled chocolate milk.

Pulsed-field gel electrophoresis established the linkage between recalled chocolate milk and a multistate invasive listeriosis outbreak during a four-product recall period. Listeria monocytogenes isolates from four hospitalized patients and an environmental dairy sample displayed AscI restriction endonuclease digestion profiles identical to that of the chocolate milk isolate.