Download - Lecture 15-Listeria Monocytogenes
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Foodborne Infections
Listeria monocytogenes
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Listeria
Genus Listeria contains six species
L. innocua, L. grayi, L. welshimeri, L. seeligeri, L. marthii
L. ivanovii
L. monocytogenes
Gram-postive rod
Facultative anaerobe
Nonsporulating Motile at 20-30C
First recognized as human foodborne pathogen in 1980s
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Psychrotroph
Growth temp range: 1-44C
Optimal temp: 30-37C
Grows best at pH >5.0
Grows in NaCl
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Listeria is ubiquitous it adapts, survives and grows in awide variety of environments
Saprophyte
Intestine
Water
Natural Habitat of Listeria
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Foods can be a natural contaminant of many foods
Raw products Produce
Raw meat
Raw milk/dairy products
Ready-to-Eat (RTE) products Because it is present everywhere in the environment, Listeria
contaminates food processing plants.
Psychrotrophic nature allows it to survive/thrive in cold storage
areas, drains, etc Deli meat
Soft cheeses
Smoked, refrigerated fish
Refrigerated, cooked shrimp
Hotdogs
Presence of Listeria in Food
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Regulation
US: FDA/USDA established zero-tolerance for Listeria
monocytogenes in RTE foods
Canada/Europe:
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Target Population YOPIs
Two types of disease: Febrile gastroenteritis healthy adults
Listeriosis YOPIs; serious, systemic disease
Infective Dose- YOPIs: 100-1000 cells
Healthy adults: 106 1010 cells
Onset: Gastroenteritis 1-7 days
Listeriosis A few days to two months
Duration of illness: Gastroenteritis 2-5 days
Listeriosis
Disease caused by Listeria
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Symptoms of Listeria infection
Febrile Gastroenteritis Mild flu-like symptoms with fever
Abdominal cramps
Diarrhea
Self-limiting
Systemic Listeriosis Primarily affects pregnant women,unborn fetuses, infants, the elderly, immunocompromisedindividuals or cancer patients taking high doses of steroids orchemotherapy
Fever, headache Meningitis, encephalitis
Spontaneous abortion or stillbirth in pregnant women
Endocarditis
Liver abcesses
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Successive Steps of Human Listeriosis
Lecuit, 2007Listeria can cross three tight barriers in
the human host
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Listeriosis and Pregnancy
Healthy pregnant women are ~20x more susceptible to L.monocytogenes than healthy nonpregnant women
Reasons:
Listeria has tropism for the placenta Listeria probably binds to special receptors on the
human placenta
Pregnant women are slightly immunocompromised
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Listeriosis and Pregnancy
Greatest risk during the 3rd trimester of gestation
Effect on fetus
Death in utero: spontaneous abortion or stillbirthDeath after birth
Survival with mental retardation
Effect on mother
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Foodborne Listeriosis is sporadic and rare
U.S.
500 - 2500 cases/yr
Mortality
20-30%
Incidence of Listeriosis
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Listeria Mechanism of Pathogenesis
1. Adhesion and
Invasion
Listeria adhesion
protein (LAP) and
other adhesionproteins
Internalin proteins
Portnoy and Tilney, 1999
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Listeria Mechanism of Pathogenesis
2. Escape from host
vacuole/phagosome
Hemolysin
Now Listeria
multiplies in host
cytosol
Portnoy and Tilney, 1999
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Listeria Mechanism of Pathogenesis
3. Formation of actin
tail and cell-to-cell
spread
Entire cycle begins
againPortnoy and Tilney, 1999
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Portnoy et al., 2002
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Brummel et al., 2006
Cossart et al., 2005
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L. monocytogenes isolated from blood, cerebrospinal
fluid, or placenta
Finding L. monocytogenes in food of infectedindividual
DNA-based methods work best and are preferred
Diagnosis of Listeriosis
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In general, antibiotics may help
However, usually medical attention is sought at
late stages of infection
Pregnant women
Antibiotics may improve survival of fetus, but
complications may still occur
Treatment for Listeriosis
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FDA-FSIS Quantitative Risk Assessment for Listeria
monocytogenes in Ready-to-Eat Foods (2003)
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Source:The FSIS Microbiological Testing Program for Ready-to-Eat (RTE) Meat and Poultry Products, 1990 - 2009
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2010 FSIS Risk Assessment
This risk assessment
indicates that of those
listeriosis cases and deaths
attributed to deli meats,
approximately 83% areassociated with deli meats
sliced at retail.
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Listeria monocytogenes
Positive Samples by SiteFood Contact Non-Food Contact
Site +* Total % Site +Total %
Slicer Blade 4 (4) 142 2.8 3-Basin Sink Ext 6 (6) 139 4.3
Deli Case 3 (2) 142 2.1 Floor-Wall Junct (3) 21 (11) 142 14.8
Case by Meat 1 (1) 26 3.8 1-Basin Sink Exterior 6 (6) 130 4.6
Deli Case Tray 4 (4) 142 2.8 Floor Wall Junct (1) 25 (9) 90 27.8
3-Basin Sink Intr 9 (7) 142 6.3 Deli Drain 28 (9) 142 19.71-Basin Sink Intr 25 (12) 130 19.2 Floor Adj to Drain 35 (13) 142 24.6
Cold Room Rack 4 (3) 142 2.8 Deli Floor 19 (9) 141 13.5
Scale Top 6 (6) 142 4.2 Cold Room Floor 26 (12) 141 18.4
Cutting Board 4 (4) 123 3.3 Cold Room Wall 4 (3) 142 2.8
Rewrap table 1 (1) 141 0.7 Cold Room Drain 34 (13) 94 36.2
Counter 3 (3) 140 2.1 Standing Water 14 (7) 76 18.4
Employee Contact Squeegee 28 (9) 104 26.9Site +Total % Cart Wheel 13 (10) 142 9.2
Slicer Knob 3 (3) 142 2.1 Hose 5 (5) 111 4.5
Case Handle 7 (5) 142 4.9 Trash Can 6 (6) 142 4.2
Total 344 3574 9.6%
*Value in parentheses indicates total positive stores
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PFGE Pattern Creation
Bacterial Chromosome (DNA) & Plasmids
fragmented by restriction enzyme
separated by electric field
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Pulsed Field Gel Electrophoresis
MM
M
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(28 entries)
ice (Opt:1.50%) (Tol 1.5%-1.5%) (H>0.0% S>0.0%) [0.0%-100.0%]
PFGE-ApaI
20.0
0
40.0
0
100.0
0
150.0
0
200.0
0
250.0
0
300.0
0
350.0
0
400.0
0
500.0
0
600.0
0
2000
1.0
0E4
PFGE-AscI
20.0
0
40.0
0
100.0
0
150.0
0
200.0
0
250.0
0
300.0
0
400.0
0
500.0
0
800.0
0
2000
2.0
0E4
Store 2
Site Locations Month
Floor next to drain2-Pre-Op
Deli area floor adjacent to the drain4-OP
Floor next to drain 3-OP
Squeegee 6-OP
Squeegee 4-OP
Floor/wall juncture under 3-basin 6-OP
Drain, deli area 6-OP
Deli area floor adjacent to the
drain
6-OP
Floor, deli area 6-OP
Wheeled carts 6-OP
Deli sink exterior (single basin) 7-OP
Drain, deli area 7-OP
Floor, deli area 7-OP
Standing water 7-OP
Deli area floor adjacent to drain 7-OP
Floor/wall juncture 1-Pre-Op
Floor/wall juncture under single-
basin
4-OP
Floor next to drain 1-Pre-Op
Floor/wall juncture 2-Pre-Op
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