Dept. Kesehatam Lingkungan

FKM UI

Microorganisms classified, growth,Microorganisms classified, growth,and ecologyand ecology

pathogenic organisms

spoilage organisms

useful organisms

Microorganisms classifiedMicroorganisms classifiedby their significanceby their significance

Dangerous microorganismsDangerous microorganismsand parasitesand parasites

Foodborne diseases

bacteria

moulds

viruses

parasites

Major bacteria causing Major bacteria causing foodborne diseasefoodborne disease

Aeromonas spp.

Bacillus cereus

Brucella spp.

Campylobacter jejuni

Clostridium botulinum

Clostridium perfringens

Escherichia coli

Listeria monocytogenes

Mycobacterium bovis

Salmonella spp.

Shigella spp.

Staphylococcus aureus

Vibrio cholerae

Vibrio parahaemolyticus

Vibrio vulnificus

Yersinia enterocolitica

Spoilage Spoilage microorganismsmicroorganisms

bacteria

yeasts

moulds

Food products madeFood products madewith useful microorganismswith useful microorganisms

fermented meats yoghurt cheese beer leavened bread soy sauce fermented soybean (tofu)

Useful microorganismsUseful microorganisms

Lactic acid bacteria (LAB) These ferment carbohydrates into organic acids which inhibit

Salmonella Staphylococcus Listeria Clostridium E. coli

LAB are found in Plants Soil Animals Human Gut

World population is

5.9 BILLION

i.e. 5 900 000 000

1 cup

of yoghurt contains

20 X this number!

i.e. 120 000 000 000

separate living

organisms.

Microorganisms are very smallMicroorganisms are very small

YOGHURT

Microorganisms are very smallMicroorganisms are very small

Cell wall

Ribosomes

Cytoplasmicmembrane

CytoplasmNuclear

body

Bacterial divisionBacterial division

1

2

3

4

5

Bacterial growth curveBacterial growth curve

Toxic

+_

+ +_ _ _ _ _ _ _ _ _ __ _ _ _ _ _

- - - - - - - - - - - -+++++++++++

Time to spoilage

Spoils

Time0

1

2

3

4

5

6

7

8

9

Lag phase Log phase Stationary phase

Lag phase(short) period of adjustment to environment

Logarithmic Growth phasegrowth begins and accelerates to a phase of rapid, constant exponential growth

Stationary phase

depletion of nutrients and accumulation of toxic

metabolic products growth is slowed to a point

where cell division and cell death are in balance Death phase

population decreases due to death of cells

Phases of bacterial growthPhases of bacterial growth

Factors affecting growth of Factors affecting growth of bacteria in foodbacteria in food

Temperature

Time

pH

Water activity (aw)

Oxygen tension

Preservatives

Microbial interactions

0°

10°

36.5°

60°

72°

100°

Boilingpoint

Pasteurisingtemperature

Freezer

Fridge

Bodytemperature

TemperatureTemperature

SAFETY SAFETY

SAFETY SAFETY

DANGERDANGER

TemperatureHotCold

How temperature affects How temperature affects growth rate of a bacterial populationgrowth rate of a bacterial population

C (Minimum)

B (Optimum)

A (Maximum)

Growth of Growth of S. typhimuriumS. typhimuriumat different temperaturesat different temperatures

Time (Days)

Lo

g N

um

ber

s

0123456789

0 1 2 3 4 5

25°20°15°10°

Temperature rangeTemperature rangefor growth of pathogensfor growth of pathogens

Temperature°CMin. Opt. Max.

Salmonella 5 35 - 37 47Campylobacter 30 42 47E. coli 10 37 48S. aureus 6.5 37 - 40 48C. botulinum (proteolytic) 10 50C. botulinum (non-proteolytic) 3.3 25 - 37B. cereus 4 30 - 35 48 - 501

432

Temperature °CMin. Opt. Max.

Penicillium verrucosum 0 20 31

Aspergillus ochraceus 8 28 37

Aspergillus flavus 10 32 42

Fusarium moniliforme 3 25 37

Temperature range for growthTemperature range for growthof toxigenic mouldsof toxigenic moulds

Growth of different bacteria at 25°CGrowth of different bacteria at 25°C

Time (Days)

0

1

2

3

4

5

6

7

8

9

0 1 2 3 4

S. typhimuriumL. monocytogenesPs. fluorescensB. cereusC. bot-ProteolyticG+ve Spoilers

Log CFU

Temperature affects bacteriaTemperature affects bacteria

Lag phase Growth rate Final cell numbers

Enzymatic and chemical composition of cells Nutritional requirements Limits for other factors influencing growth

through the change in

Effect of salt concentration on time to botulinum toxin production

Salt Concentration (%)

0

2

4

6

8

10

12

14

16

0 0.5 1 1.5 2

10°C14°C18°C24°C

Limits of pH for growth of pathogens

pHMin Max.

Escherichia coli 4.4 8.5Salmonella typhi 4 - 4.5 8 - 9.6Bacillus cereus 4.9 9.3Clostridium botulinum 4.6 8.5Staphylococcus aureus 4 9.8Saccharomyces cerevisiae 2.3 8.6Aspergillus flavus 2.0 11.2Fusarium moniliforme 2.5 10.7Penicillium verrucosum 2.0 10.0

Definition of water activity (aDefinition of water activity (aww))

aw is the ratio of the water vapour pressure of the food (p) to that of pure water (po) at the same temperature.

aW = p / po

NaCl and glucose concentrations andcorresponding aw values at 25°C

1.00 0.00 0.00 0.99 1.74 8.90 0.98 3.43 15.74 0.96 6.57 28.51

0.94 9.38 37.83 0.92 11.90 43.72 0.90 14.18 48.54 0.88 16.28 53.05 0.86 18.18 58.45

aW % w/w % w/w NaCl Glucose

Range of aW in foodsand their microbial flora

aw range foods microbial flora

> 0.98

Fresh meatsFresh fishFresh fruitsFresh vegetablesCanned vegetables in brine Canned fruit in light syrup (<3.5% salt, 26% sugar)

(C. perfringens, Salmonella)

(Pseudomonas)

0.93 - 0.98 Fermented sausagesProcessed cheeseBreadEvaporated milkTomato paste(10% salt, 50% sugar)

(B. cereus,C. botulinum,Salmonella)lactobacilli, bacilli andmicrococci

Range of aW in foodsand their microbial flora

aw range foods microbial flora

0.85 - 0.93 S. aureus

Mycotoxin producing mouldsSpoilage yeasts and moulds

Dry fermented sausagesRaw ham (17% salt, saturated sucrose)

0.6 - 0.85Xerophilic fungi

HalophilesOsmophilic yeasts

Dried fruitFlourCerealsSalted fishNuts

< 0.6 No growth but may remain viable

ConfectioneryHoneyNoodlesDried egg, milk

Key messages

Temperature, pH, water activity and oxygen tension are the principal factors affecting microbial growth

There are optimum ranges for these parameters

These optima are interdependent

They can be selected to inhibit the growth of certain organisms within limits related to the palatability of food

Certain foods are suited for the growth of certain flora

Some toxigenic mouldsSome toxigenic mouldscausing foodborne diseasecausing foodborne disease

Aspergillus spp.

Fusarium spp.

Penicillium spp.

( Main sources - fruits, nuts and grains )

Major virusesMajor virusescausing foodborne diseasecausing foodborne disease

Hepatitis A and E viruses

Small Round Structured Viruses (e.g. Norwalk agent)

Rotavirus

Polio virus

Virus structureVirus structure

Protein Capsule

Nucleic acid(DNA or RNA)

Poliovirus

Hepatitis-A virus

RotavirusNorwalk-like or

SRSV

Virus levels required forVirus levels required forinfection and detectioninfection and detection

infection10 -100 particles / ml

detection105 - 106 particles / g(by electron microscopy)

104 - 105 particles / g(by radioimmunoassay)

Major parasitesMajor parasitescausing foodborne diseasecausing foodborne disease

• Cryptosporidium

• Entamoeba histolytica

• Giardia

• Toxoplasma

• Fasciola

• Fasciolopsis

• Haplorchis

• Opisthorchis

• Paragonimus

• Cysticercus cellulosae

Protozoa

Helmints• Angiostrongylus

• Anisakis

• Ascaris

• Capillaria

• Gnathostoma

• Trichinella

Nature of bacteria, moulds, virusesNature of bacteria, moulds, virusesand parasites - Key messages (1)and parasites - Key messages (1)

foodborne diseases are caused by bacteria, moulds, viruses, and parasites

certain microorganisms are of greater significance than others for humans

bacteria and moulds multiply on foods andmay produce toxins

understanding the factors controlling growthof microorganisms allows us to control themin food

bacteria may be harmful or useful

bacteria, yeasts and moulds can be usedto preserve foods

lactic acid bacteria secrete lactic and other organic acids

organic acids inhibit pathogens in food andin the gut

viruses and parasites do not grow in food

Nature of bacteria, moulds, virusesNature of bacteria, moulds, virusesand parasites - Key messages (2)and parasites - Key messages (2)

Microbiological ecologyMicrobiological ecology

Microbiological ecologyMicrobiological ecology

Microbes are everywhere air water food soil humans (e.g. gut, nose,

skin) surfaces

The The SalmonellaSalmonella (non typhi) cycle (non typhi) cycle

Effluent, slurry and sludge

Imported animal /

vegetable protein

Slaughter houses

Human food

Wildlife reservoirs

Animal importation ManPets

Farm

animals

Imported food

Animal feedsMeat / bone meal, dried

poultry waste, etc.

Offal

Transmission of Transmission of CampylobacterCampylobacter

Raw materials Raw materials will have a normal florawill have a normal flora

meat poultry fish and shellfish cereals milk egg products vegetables, fruits and nuts spices oils and fats water

Meat and meat products hazardsMeat and meat products hazards

Salmonella S. aureus Yersinia enterocolitica C. perfringens C. botulinum Pathogenic E. coli Listeria

monocytogenes Parasites

The contamination chain for meatThe contamination chain for meat

Cross contamination

Cross contamination

Infected portion

Butcher

Jointed meat

Blood and tissue drip

Pass

Slaughter

Cross contamination

Cross contamination

Cross contamination

Fail --diseased or

contaminated

Hazards in milkHazards in milk

Mycobacterium Brucella Salmonella L.

monocytogenes E. coli S. aureus Bacillus Clostridium Campylobacter

Poultry and poultry productsPoultry and poultry products

Salmonella

Campylobacter

C. perfringens

S. aureus

Y. enterocolitica

L.

monocytogenes

Eggs and egg products - hazardsEggs and egg products - hazards

Salmonella!

Fish and shellfish - hazardsFish and shellfish - hazards

Bacteria C. botulinum type E Vibrio parahaemolyticus Vibrio vulnificus Vibrio cholerae L. monocytogenes

Parasites Viruses

Hepatitis A virus Norwalk virus

Vegetables, fruits and nuts - hazardsVegetables, fruits and nuts - hazards

Bacteria Salmonella Shigella V. cholerae L. monocytogenes Enterotoxigenic E.coli Clostridium botulinum

Hepatitis A and other enteric viruses

Parasites

Moulds

Moulds

Salmonella

B. cereus

Cereals -Cereals - hazards hazards

C. perfringens

B. cereus

Salmonella

Moulds

Spices - hazardsSpices - hazards

Ecology of foodborne pathogensEcology of foodborne pathogensKey MessagesKey Messages

Some originate from animals Salmonella Campylobacter E. coli

Some come from plants and soil Moulds B. cereus C. botulinum

Ecology of foodborne pathogensEcology of foodborne pathogensKey MessagesKey Messages

Some originate in the sea V. parahaemolyticus C. botulinum Type E V. cholerae

Some originate from man Viruses S. typhi S. aureus Shigella