lecture 15-listeria monocytogenes

8/13/2019 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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2. Escape from host

vacuole/phagosome

Hemolysin

Now Listeria

multiplies in host

cytosol

Portnoy and Tilney, 1999

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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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lecture 15-listeria monocytogenes

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