Introduction
Listeria monocytogenes is a Gram-positive, nonspore forming
rod that can cause a disease in humans that is known
as listeriosis. Although there are much data obtained from epidemics
of listeriosis, most of the cases of listeriosis in humans
are isolated and sporadic (Painter and Slutsker 2007). CDC (2009)
recorded 723 reported cases of listeriosis in 2008, and 85 cases
in 2009 as of the week ending March 21, 2009. Mead and others
(1999) estimated that many more cases of listeriosis occurred
than were reported and therefore projected that 2518
cases of listeriosis occur each year, with 504 cases resulting in
death.