1. Listeria monocytogenes in seafood
A Presentation for
Specific and Emerging Topics in Food Microbiology
Mansooreh Jami, Ph.D Student
Institute of Food Science
Department of Food Science and Technology
BOKU-University of Natural Resources and Life Sciences
Specific Emerging Topics in Food Microbiology I
Listeria monocytogenes in seafood
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27, May 2013-SS
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2. The Listeria genus
Six identified species
L. monocytogenes, L. innocua, L. welshimeri, L.
seeligeri, L. ivanovii, and L. grayi
Primary human pathogen
L. monocytogenes
• Gram (+), non-spore, motile, rod
Aerobic and facultative anaerobic
Psychotropic and halo-tolerant
Specific Emerging Topics in Food Microbiology I
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3. Significance of L. monocytogenes
Ubiquitous presence
Widely distributed in the environment
L. monocytogenes is found in relatively low number but under
certain conditions facilitate higher number
Soil & vegetation
Fecal water
Animal feed
Foodborne pathogen that causes listeriosis
Listeriosis is a serious infection caused by eating foods
contaminated with the bacterium L.monocytogenes.
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4. Symptoms
This disease affects primarily pregnant women, newborn,
and adults with weakened immune systems.
Pregnant women
Flu-like illness, fever, muscular pain, headache or asymptomatic
Spontaneous abortion, stillbirth, septicemia, meningitis.
Non-pregnant adults
Mild gastroenteritis, septicemia, meningitis.
Specific Emerging Topics in Food Microbiology I
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5. Food-borne listeriosis
Foodborne illness caused by L. monocytogenes
14 serotypes of L. monocytogenes have been designated
1/2a, 1/2b, 1/2c, 3a, 3b, 3c, 4a,4b, 4bX, 4c, 4d, 5, 6a, 6b
Serotype 1/2a, 1/2b, and 4b account for 96% of human
infections in the United States
Specific Emerging Topics in Food Microbiology I
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6. Circulation of L. monocytogenes
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7. Factors affecting growth and survival
Temperature
Growth range = -1 to 45°C
Optimum = 30 to 37°C
Psychrotrophic (refrigeration temperature; <5 °C)
Mesophilic (room to body temperature; 18-38 °C)
Temperatures < 0 moderately inactivate LM
LM can survive freezing
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8. Factors affecting growth and survival
Acidity
Typical pH range is 5.0 to 9.6
Optimum =neutral conditions ~6.0 - 7.0
Growth at pH of <4.3 has not been demonstrated
LM can tolerate lower pH when kept at near refrigeration temperatures
(vs. room & body temperatures)
Most strains of LM are unlikely to grow in food products with pH < 5.2
Specific Emerging Topics in Food Microbiology I
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9. Factors affecting growth and survival
Water activity
Water activity (aw)
LM grows well at aw of >0.95; can multiply at aw of 0.90
Some LM can survive at aw of <0.90
Salt concentration
Growth at 10%
Survival at 25.5%
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10. L. monocytogenes in seafood
Fresh seafood
Raw fish
Raw mollusc
Raw crustacean
Ready to eat seafood
Cold smoked fish
Hot smoked fish
Gravad
Semi processed seafood
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11. Fresh seafood products
Listeria as indigenous pathogens in aquatic environment
The prevalence of L. monocytogenes in raw fish is quite low,
ranging from 0 to 1% (Autio et al., 1999) to 10% (Jemmi &
Keusch, 1994). An overall prevalence 3% of L.
monocytogenes was observed in European fish (Davies et al.,
2001). Swetha et al., 2012; L. monocytogenes was isolated
from 8 % fish samples.
Different geographical area, Different type of products
The problems can arise when handling, processing or storing
conditions provide favourable conditions for the growth of
the pathogenic bacteria.
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12. L. monocytogenes in lightly preserved seafood
15,000 samples
1988-2007
•
•
•
Cold smoked fish: Aw (0.89 – 0.99), pH (3.1-7.2), Temperature (25-28 ºC)
Hot smoked fish: Aw (0.89 – 0.99), pH (4.1 – 8.4), Temperature (70-90 ºC)
Gravad: Aw (0.97-0.99), pH (6.1-6.3)
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13. Seafood/lightly preserved seafood implicated in human listeriosis
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14. EU criteria for L. monocytogenes
a n = number of units comprising the sample;
c = number of sample units giving values over m or between m and M
bm=M
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15. Conclusion
The prevalence of L. monocytogenes generally increases
along the food production chain, mainly due to crosscontamination in the production plants making this pathogen
a major threat to the seafood industry.
Attention must be paid to the design of food-processing
equipment and to the effectiveness of the cleaning and
disinfecting procedures in the production facilities, based on
the known imperative preventive measures, such as Good
Agricultural Practices (GAP) in the primary production, Good
Hygiene and Manufacturing Practice (GMP) and also Hazard
Analysis and Critical Control Points (HACCP).
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16. Thanks for Your Attention!
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