bacterium is found in soil, silage, and other environmental sources.
L. monocytogenes is quite hardy and resists the deleterious
effects of freezing, drying, and heat.
is diagnosed when the organism is isolated from blood, cerebrospinal
fluid, or an otherwise normally sterile site (e.g. placenta, fetus).
symptoms of listeriosis include septicemia, meningitis, encephalitis,
and intrauterine or cervical infections in pregnant women, which
may result in spontaneous abortion (2nd/3rd trimester) or stillbirth.
Infections are usually preceded by influenza-like symptoms including
persistent fever. Symptoms such as nausea, vomiting, and diarrhea
may precede more serious forms of listeriosis or may be the only
bacterium enters the host's white blood cells and becomes blood
borne.. Its presence intracellularly in cells also permits access
to the brain and probably transplacental migration to the fetus
in pregnant women.
severity of L. monocytogenes infectiousness depends on
its ability to survive and multiply in phagocytic host cells.
is only positively diagnosed by culturing the organism from blood,
cerebrospinal fluid, or stool (although the latter is difficult
and of limited value).
has been associated with
such foods as raw milk, incompletely pasteurised milk, cheeses
(particularly soft-ripened varieties), ice cream, raw vegetables,
fermented raw-meat sausages, raw and cooked poultry, raw meats (all
types), and raw and smoked fish. Because it can grow at temperatures
as low as 3°C it may multiply in refrigerated foods.
listeric meningitis occurs, the overall mortality may be as high
as 70%; from septicemia 50%, from perinatal/neonatal infections
greater than 80%. In infections during pregnancy, the mother usually
at risk for listeriosis include: pregnant women/fetus - perinatal
and neonatal infections; persons immunocompromised (by corticosteroids,
anticancer drugs, graft suppression therapy, AIDS; cancer patients
- leukemic patients particularly); less frequently reported (- diabetic,
cirrhotic, asthmatic, and ulcerative colitis patients); the elderly;
and occasionally normal people--some reports suggest that normal,
healthy people are at risk, although antacids or cimetidine may
health alert for Hispanic pregnant women concerns the risk of
listeriosis from soft cheeses