Biomedical Engineering Reference
In-Depth Information
of invasive listeriosis may remain asymptomatic for days to months. Early symp-
toms can include mild fl u-like fever, nausea, headaches, and body aches between 3
and 70 days after consumption of contaminated food. Disease progresses as the
bacteria cross the blood-brain barrier, resulting in meningitis (infl ammation of
the membrane around spinal and brain tissues) and/or encephalitis (swelling of the
brain). Symptoms may include confusion, seizures, or impaired motor function.
Approximately 20-30 % of listeriosis cases result in death (Rocourt et al.
2003
;
Silk et al.
2012
).
Globally, listeriosis will remain an important foodborne illness due to the fact
that the vulnerable population is growing. Advances in medicine and nutrition help
immunocompromised persons with advanced age, disease, or under medical treat-
ment live longer. European Union member countries reported a 19 % increase in
listeriosis cases from 2008 to 2009 (EFSA
2011
). In the USA and Europe, there has
been a signifi cant increase in the number of listeriosis cases in adults >65 years of
age (Little et al.
2010
). Among listeriosis cases that occurred in the USA between
2004 and 2009, over 50 % of cases were in adults >65 years of age; this increased
to 58 % of reported cases from 2009 to 2011. Specifi cally, there were 400 cases of
listeriosis in adults >65 years and 234 of nonpregnancy associated cases in adults
<65 years from 2004 to 2009. However, from 2009 to 2011, there were 950 cases
and 474 nonpregnancy associated cases in adults >65 and <65 year of age, respec-
tively (Silk et al.
2012
,
2013
).
Pregnant women are 8-18 times more likely to suffer an invasive infection than
healthy, nonpregnant women (Southwick and Purich
1996
; Silk et al.
2012
). During
the third trimester of gestation, the mother's immune system is naturally suppressed
to prevent her body from rejecting the fetus. An infected mother may experience
fl u-like symptoms (e.g., fever, nausea, body aches), but the greatest danger is to the
fetus since
L. monocytogenes
has a tropism for the placenta resulting in fetal infec-
tion (Smith
1999
). High levels of
L. monocytogenes
in the placenta can result in
spontaneous abortion or still birth; infected surviving neonates may suffer mental
retardation (Farber and Losos
1988
; Southwick and Purich
1996
; Lecuit
2007
).
While the overall rate of listeriosis has not signifi cantly increased or decreased in
the USA since 2004, there was a signifi cant increase in pregnancy-associated
listeriosis in Hispanic women from 2004 to 2009 (Silk et al.
2012
), and 43 % of
pregnancy-associated listeriosis cases from 2009 to 2011 occurred in Hispanic
women (Silk et al.
2013
).
5.2
L. monocytogenes
in Foods and Food Systems
5.2.1
L. monocytogenes
Prevalence in the Environment
Raw ingredients and water are both potential sources of contamination (Lawrence
and Gilmour
1995
; Ojeniyi et al.
1996
). Researchers have isolated
L. monocyto-
genes
from 20 to 35 % of ruminant farm environment samples and from >20 % of
