Specific Emerging Topics in Food Microbiology I Listeria monocytogenes in seafood I 27, May 2013-SS 1

Listeria monocytogenes in seafood

Mansooreh Jami, Ph.D Student

Institute of Food Science

Department of Food Science and Technology

BOKU-University of Natural Resources and Life Sciences

A Presentation forSpecific and Emerging Topics in Food Microbiology

Specific Emerging Topics in Food Microbiology I Listeria monocytogenes in seafood I 27, May 2013-SS 2

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

The Listeria genus

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Ubiquitous presenceWidely distributed in the environmentL. monocytogenes is found in relatively low number but under certain conditions facilitate higher numberSoil & vegetationFecal waterAnimal feed

Foodborne pathogen that causes listeriosisListeriosis is a serious infection caused by eating foods contaminated with the bacterium L.monocytogenes.

Significance of L. monocytogenes

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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.

Symptoms

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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

Food-borne listeriosis

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Circulation of L. monocytogenes

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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

Factors affecting growth and survival

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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

Factors affecting growth and survival

Specific Emerging Topics in Food Microbiology I Listeria monocytogenes in seafood I 27, May 2013-SS 9

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%

Factors affecting growth and survival

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Fresh seafoodRaw fishRaw molluscRaw crustacean

Ready to eat seafoodCold smoked fishHot smoked fishGravad

Semi processed seafood

L. monocytogenes in seafood

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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.

Fresh seafood products

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• 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)

L. monocytogenes in lightly preserved seafood

15,000 samples

1988-2007

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Seafood/lightly preserved seafood implicated in human listeriosis

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a n = number of units comprising the sample; c = number of sample units giving values over m or between m and M b m = M

EU criteria for L. monocytogenes

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ConclusionThe prevalence of L. monocytogenes generally increases along the food production chain, mainly due to cross-contamination 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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Thanks for Your Attention!

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