Transcript Food borne diseases

Practical 9
Food borne diseases
SPC method
Relationship of Microorganisms and food
1- Beneficial/ desirable( make food)
- Lactobacilli bacteria in fermented food
(yoghurt, pickles)
- Yeast Saccharomyces in Bread and baking
2- Deteriorated/ undesirable (spoilage)
- Non-pathogenic
- Fungi, Pseudomonas, Proteus, Bacillus
3-Pathogenic or Toxogenic: cause disease
Conditions for Spoilage
• Water, pH , temperature ,physical structure.
Water•
pH •
Physical structure•
Oxygen•
temperature•
Spoilage of food
• Organisms that cause spoilage:
Pseudomonas , Proteus, Serratia, lactobacillus
micrococcus, fungi such as Aspergillus,
Rhizopus, yeast.
• Spoilage appears as :
• greening , Rotting , souring moldy appearance,
discoloration, bad smell.
Foodborne disease
is any illness resulting from the consumption of
food contaminated with one or more diseaseproducing agents( bacteria, parasites, viruses,
fungi and their products toxic substances)
• Two primary types
– Food infection : due to presence of living organism
– Food poisoning due to presence of toxins
(staphylococcal, botulism, Clostridium perfringens, and
Bacillus cereus)
Food borne infections vs. intoxication
Infections
• Bacterial / Viral / parasite
Intoxications/ Poisoning
• toxins ( natural / preformed bacterial /
chemical)
• No invasion or multiplication
• Invade and or multiply in lining
of intestine
• Incubation period- hours to days • Incubation period- minutes to hours
• S/s – Diarrhea , nausea, vomiting , • S/s – Vomiting , nausea, diarrhea ,
abdominal cramps, fever
diplopia, weakness, resp. failure ,
numbness, sensory/motor dysfunction
• Not communicable
• Communicable-spreads from
person to person
• Factors-inadequate cooking , improper
handling temperatures
• Factors-inadequate cooking, cross
contamination , poor personal
hygiene , bare hand contact
The
numbers
and
types
of
microorganisms present on a food are
affected by the following factors;
• The general environment which the food was
originally obtained from
• The microbial content of the food in the
unprocessed state
• The sanitary conditions during the processing
• The adequacy of subsequence packaging,
handling and storage conditions.
General facts about Food borne
diseases
• Every person is at risk of food borne illness.
• No long-term health threat to average person
• May be serious for very young, very old, people with
long term illness
• Reaction may occur in a few hours or up to several days
after exposure
Symptoms
• Abdominal cramps, headache, vomiting, diarrhea (may
be bloody), fever, death
After Ingestion of bacteria
1. Will be sick within 6-72 hours after eating
contaminated food. (NOT usually sick
immediately after eating!)
2. Symptoms usually last 4-7 days
3. Most recover without antibiotics or treatment.
4. Diarrhea can be severe enough to hospitalize
person (dehydration)
Sources of Pathogens in Food
1-Food itself: soil contaminated, water irrigation
e.g. Vibrio, Brucella, Salmonella
2-Food Handlers :Cooks, workers, waiters.
e.g. Staph, Salmonella, Shigella, hepatitis A
3- Environment:Food storage, sanitation of
markets, utensils , benches,food transport
e.g. Bacillus, Yersinia, Campylobacter
Food risky to food borne disease
• Fermented/ pickled food
• Sausages, pickled vegetables
• Raw contaminated food
• Raw meat , , milk, salads, chicken
• Undercooked food
steaks, eggs, creams, fish
• Readymade food
• Canned, frozen , ready made sandwiches
What to do in case of food borne dis.
• Look for pathogenic organisms from different
samples
• Look for toxins in food
• Must take samples from
1- Patients
2- Handlers
3- Food Leftovers
4- Utensils , boards, storage places
Detection of M.O. in food
• Conventional cultural techniques
– Standard plate count (SPC)
– Most probable number (MPN), MFT
• Rapid tests biochemical, immunological
– Commercial kits : MMO-MUG, Elisa
• Molecular techniques
– Nucleotide hybridization
– Polymerase Chain Reaction (PCR)
Comparison of detection methods
• All methods must be must be rapid and
sensitive
• Methods include:
– Culture techniques – may be too slow
– Rapid biochemical techniques- rapid
– Immunological techniques - very sensitive
– Molecular techniques – new, sensitive and
specific but need reduce false positives
Evaluating the sanitary
quality of foods
• It is impractical to analyze all food for
presence of pathogens
• Use of indicator organisms
• If present in greater than allowable No’s, it
indicates that food is not of acceptable sanity
quality. If absent, food is almost safe
• SPC method can be used to test different
organisms.
Standard plate count(SPC)
The process of using standard plate count is to
dilute samples of the material to be tested
with the agar medium, after 48 hours of
incubation at 35c visible colonies are counted
Homogenise food sample(50g of food+450ml of S. saline)
Make ten fold serial dilutions from mixed sample
Plate on suitable selective media
Incubate at 35oC, for24 h.
Colony count
Rapid tests
• Commercial kits: many
• Faster than conventional method
– e.g. the MMO-MUG method for Coliform testing
Negative
E. coli
Positive
Negative
Positive
Total Coliform
MMO-MUG method
• A chemically defined media containing the sugar-dyes ONPG
and MUG are used in the MMO-MUG test procedure. After
incubation, Coliform bacteria break down the ONPG sugar
dye and cause the clear media, to turn a distinct orange
color.
• A unique feature of the MMO-MUG method is the ability to
determine the presence of the bacterium E. coli directly,
without additional culture media or incubation. When a
total Coliform positive (orange) MMO-MUG sample jar is
placed in ultraviolet light, the sample will fluoresce a distinct
blue color when E. coli are present.
Pathogens of Most Concern on Fresh
Produce
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Salmonella
Shigella
Escherichia coli
Campylobacter
Yersinia enterocolitica
Staphylococcus aureus
Clostridium species
Bacillus cereus
Vibrio species
Viruses (Hepatitis A, Norwalk, Rota )
Parasites/Protozoa- (Giardia, Entamoeba,
Toxoplasma, Sarccystis, Isopora, Cryptosporidium,
Eimeria, Cyclospora)
General Control of food borne disease
in markets
• Food inspection
• Check Handlers health
• Education and training for food handlers and
public
• Market sanitation
• Proper transport and storage methods
Food control In the Home
• Drink pasteurized milk and juices
• Wash hands carefully and frequently
– After using the bathroom, Changing infant’s
diapers, Cleaning up animal feces, before
preparing food & before eating
• Wash raw fruits and vegetables before eating
• After contact with raw meat or poultry
– Wash hands, utensils and kitchen surfaces with
hot soapy water
In the Home
• Cook beef/beef products thoroughly
– Internal temperature of 70o C
• Cook poultry and eggs thoroughly
– Internal temperature of 80oC
• Eat cooked food promptly
• Defrost meats in the refrigerator
• Refrigerate leftovers within 2 hours after cooking
• Store in shallow containers so that the contents
gets cooled evenly throughout
Five general keys to Safer food
1. Keep Clean –
Wash hands before handling food and often during preparation
Wash hands after going to toilet
Wash n sanitize all surfaces n equipment for food preparationprotect kitchen from insects , pets
2. Separate raw and cooked foodSeparate raw meat , poultry n seafood from other foods
Use separate utensils for handling raw foods
Store food in containers to avoid contact between raw and
cooked foods
3. Cook Thoroughly –
esp. Meat , poultry , eggs and Seafood
Bring soups n stews to boiling (ensure>70degree temp)
Reheat cooked food thoroughly
Five Keys to Safer Food
4. Keep food at safe temperature Don't leave cooked food at room temp.>2 hours
Prompt refrigeration of cooked n perishable food
Keep cooked food piping hot(>60 de.) prior to serving
Don’t store food too long even in refrigerator
Don’t thaw frozen food at room temperature
5. Use safe water and raw materials-
• Use safe water or treat to make it safe
• Select fresh and wholesome fruits
• Choose foods processed for safety - pasteurized milk
• Wash fruits n vegetables if eaten raw
• Don’t use food beyond expiry date
Prevention of Food Borne diseases
WHO ‘ten golden rules
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Food processed for safety
Thoroughly cook
Eat immediately
Store carefully
Reheat thoroughly
No contact between raw & cooked
Wash hands
Keep food preparation surfaces clean
Protect from pests
Use potable water
CONCLUSIONS
1. It is important to realize that with any of the methods of analysis
for pathogen or indicator, there is no absolute guarantee of
success.
2. The organisms under test can be missed completely (false
negative) or other organisms can mimic positive results giving
rise to false positives.
3. Developing and improving methods of analysis for pathogens
and indicators is an area of intensive and continuing research.
4. This is particularly the case where `new’ pathogens are
concerned and a widely accepted method needs to be
established.
5. Even when techniques are well established, research continues
to try and improve sensitivity, eliminate false positive and
reduce the time taken to obtain results.