November15 2005 Listeria Monocytogenes

8/11/2019 November15 2005 Listeria Monocytogenes

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Listeria monocytogenes

November 15, 2005

Textbook Chapter 13

Introduction

First outbreak Coleslaw (1981)

Outbreaks were soon linked to cheeses,

luncheon meats, chicken nuggets, and fish~2000 reported cases/year

~500 fatalities/year (25%)

Serious threat to high-risk population

Annual costs for listeriosis $209-233 million Excluding recalls and listeria control

Why is L. monocytogenesof interest?

Ubiquitous

Recalcitrant

High mortality

Zero tolerance

Model intracellular pathogen

The Genus Listeria

Clostridium sub-branch Staphylococcus, Streptococcus, Lactobacillus, and

Brochotrix, and Listeria

Listeria species (6) Monocytogenes, ivanovii, innocua, seeligeri, welshimeri, and

grayi

Identification Biochemical tests

Hemolysis

Rapid identification tests

Fluorescence in situ hybridization (FISH) for wholecell identification of Listeria monocytogenes


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Listeria monocytogenes

Gram-positiveCatalase-positive

Non-sporeformingSlim rodTumbling motility at 25oCUmbrella motility in semi-soft agarBeta-hemolytic on blood agarColonies are smooth, convex, circular, bluish-translucent appearance on nonselective agars; atypicalrough colonies form filaments

Dramsi et al. Rev. Cell

Dev. Biol. 14: 137-166.

Umbrella Motility

Hemolysis Serotypes

13 serotypes

95% of Listeriosis (clinical and foodborne) outbreaksare caused by 3 serotypes: 1/2a, 1/2b, 4b

Almost exclusively all the major foodborne outbreakscaused by serotype 4B strains

42-44% of clinical cases are caused by serotype 4Bstrains

4B strains are rarely found in foods!Commercial antisera for Type 1 and 4 (somatic antigen)

Definitive serological identification through state labs toCDC (PulseNet)

Susceptibility to Physicaland Chemical Agents

Temperature Growth from 0 to 45oC

Slow growth at colder temperatures (Table 13.2) 4oC doubling time of 43 h

10oC doubling time of 6.6 h

37oC doubling time of 1.1 h

Survival and injury during frozen storage depend onfood and the freezing rate

Killed at temperatures of >50oC

Susceptibility to Physicaland Chemical Agents

pH Grows at pH values as low as 4.4

Survives at pH values below 4.3

Organic acids (at 0.1%) inhibit growth

Water activity (aw) Grows best at aw of >0.97

Minimum aw for growth is 0.93 (for most strains)

May survive for long periods at aw values of 0.83


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Susceptibility to Physical andChemical Agents

Salt Grows to high levels at moderate salt concentrations

(6.5%) Can grow in the presence of 10-12% salt

Survives for long periods at higher saltconcentrations

Lowering the temperature increases survival in highsalt concentrations

Cured meats are very hospitable environments for listeria

Foods Associatedwith Listeriosis

Milk products Raw milk, pasteurized milk, pasteurized chocolate milk

Cheeses Feta, Camembert, Blue

Meat and poultry products Raw meat and poultry

Cooked ready-to-eat meat and poultry (sporadic andepidemic listeriosis)

Unheated frankfurters and undercooked chicken (sporadiclisteriosis)

Seafoods Fresh, frozen, and processed seafoods

Specific Foods Associatedwith Listeriosis (Table 13.3)

Cheese

Fish

Raw milk

Turkey franks

Smoked fish

Deli meat

Vegetable rennet

Ice creamHomemade sausage

Alfaalfa tablets

Chicken nuggets

Cold roe

Cook-and-chill chicken

Deli salads

Hot dogs

Human breast milk

Pork sausageSalted mushrooms

Control Measures forL. monocytogenes

Physical control measures Post process pasteurization

Irradiation

Hydrostatic pressure

Alternative control measures Sodium lactate

Sodium acetate

Liquid smoke Monoglycerides

Lysozyme

Biopreservation*

Sources of L. monocytogenes inthe Environment

Figure 13.1. Potential routes oftransmission of L. monocytogenes


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Food Processing Plants

Entry Soil (shoes, clothing, vehicles, etc.)

Contaminated raw plant and animal tissue Human carriers

Popular locations Floor drains

Condensed and stagnant water

Floors

Residues

Processing equipment

Surfaces (stainless steel, glass, and rubber)

Biofilms on Surfaces Commonly Foundin the Food Processing Industry Stainless Steel

Biofilms on Surfaces Commonly Foundin the Food Processing Industry Stainless Steel

Biofilms on Surfaces Commonly Foundin the Food Processing Industry Glass

Biofilms on Surfaces Commonly Foundin the Food Processing Industry Nylon

Prevalence and RegulatoryStatus of L. monocytogenes

Figure 13.2. Causes of USDA Recalls, 1997

Listeria tolerance levels EU

UK & USA

Table 13.4. Relative risk of listeriosis for differentpopulations

Box. 13.2. The present dilemma


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Human Carriers

Healthy people

Pregnant women

Patients w/ gastroenteritis

Slaughterhouse workers

Laboratory workers

Food handlers

Patients undergoing hemodialysis

Human Carriers Cont.

Primary transmission: food-first victim

Secondary transmission: feces-second victim

Major Foodborne Outbreaks

Canadian coleslaw outbreak

Mexican style cheese outbreak

Switzerland soft cheese outbreak

UK pt outbreak

US 10-state deli turkey outbreak

Characteristics of Disease

Low-grade flu-like infection not serious, except inpregnant women (who abort)

Listeric meningitis headache, drowsiness, coma

Perinatal infection

Encephalitis

Psychosis

Infectious mononucleosis

Septicemia

Primary Manifestationsof Listeriosis in Humans

Meningitis

Abortion

Perinatal septicemia

Others Influenza like


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Meningitis

Onset: sudden

Symptoms:

Severe headache Dizziness

Stiff neck or back

Incoordinaation

Coma

Without therapeutic intervention, death usually ensues

Abortion

Symptoms in the last half of pregnancy : Sudden chills Rise in temperature

Sore throat Headache Dizziness Lower back pain Discolored urine Diarrhea

Premature delivery of stillborne or acutely ill infantAfter parturition, mother is asymptomatic and there is no furthercomplications

Perinatal Septicemia

If born alive, infant often dies within a fewminutes or hours after delivery

Symptoms reflect disturbances of respiratory,circulatory or central nervous system

If infant survives, meningitis usually develops,which generally terminates fatally or leads

permanent mental deficiency

Infectious Dose andSusceptible Populations

Animal vs. human Mice

ID50103-107

mouse death assay at 109/mouse

Nonhuman primates 109

Noticable illness (loss of apetite, septicemia, irritability, occasional diarrhea)

Human Dependent on host and strain Usually >100 cfu/g food Range: 103-109

Exceptions exist


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Pathogenicity of L. monocytogenes Actin Tail

Dramsi et al. Rev. Cell Dev. Biol. 14: 137-166.

Specific Genes MediatePathogenicity

hyl SH-activated hemolysin (58 kDa)plcA phosphatidyl inositol specific phospholipase C (38 kDa)plcB lecithinase (29 or 32 kDa)mpl lecithinase-specific metalloproteaseactA surface protein (actin assembly) (90 kDa)inlA internalin (80 kDa)

prfA positive regulatory factor of hyl, plcA, plcB, and mpl(27 kDa DNAbinding protein)imt

inlAB

Imaiap invasion associated protein

Characterization of MolecularDeterminants of Pathogenesis

Genomic Subtraction/Subtractive Hybridization

Characterizing Putative Molecular Determinantsof Pathogenesis

Prevention of Food-RelatedListeriosis

Dietary recommendations for the prevention of listeriosis forpersons with increased susceptibility Avoid eating raw or partially cooked foods of animal origin

Avoid cross-contamination between raw and cooked foods during foodpreparation and storage

Reheat leftovers until too hot to touch

Avoid soft cheeses such as feta and Mexican-style cheeses. Hardcheeses, cottage cheese, and cream cheese can be eaten withoutconcern about the risk of listeriosis

Raw vegetables should be thoroughly washed before eating

November15 2005 Listeria Monocytogenes

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