Food borne diseases

SPC method

Relationship of Microorganisms and food

• Pathogenic or Toxogenic: cause disease

• Beneficial/ desirable( make food)– Lactobacilli bacteria in fermented food(yoghurt,

pickles)– Yeast Saccharomyces in Bread and baking

• Deteriorated/ undesirable– Non-pathogenic: Spoilage– Fungi, Pseudomonas, Proteus, Bacillus

Conditions for Spoilage

•Water•pH •Physical structure•Oxygen•temperature

• 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 appear as greening , moldy appearance, Rotting, discoloration, souring , bad smell.

Foodborne disease

is any illness resulting from the consumption of food contaminated with one or more disease-producing 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 poisoning)

Food borne infections vs. intoxication

Infections• Bacterial / Viral / parasite

• Invade and or multiply in lining of intestine

• Incubation period- hours to days

• S/s – Diarrhea , nausea, vomiting , abdominal cramps, fever

• Communicable-spreads from person to person

• Factors-inadequate cooking, cross contamination , poor personal hygiene , bare hand contact

Intoxications• toxins ( natural / preformed bacterial /

chemical)• No invasion or multiplication

• Incubation period- minutes to hours

• S/s – Vomiting , nausea, diarrhea , diplopia, weakness, resp. failure , numbness, sensory/motor dysfunction

• Not communicable• Factors-inadequate cooking , improper

handling temperatures

• The general environment which the food was

originally obtained from• The microbial content of the food in the unp

rocessed state• The sanitary conditions during the processing• The adequacy of subsequence packaging, ha

ndling and storage conditions.

The numbers and types of microorganisms present on a food are affected by the following factors;

General facts • 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 bacteria1. Will be sick within 6-72 hours after

eating contaminated food. (NOT usually sick immediately after eating!)

2. Symptoms usually last 4-7 days3. Most recover without antibiotics4. Diarrhea can be severe enough to

hospitalize person (dehydration)

Sources of Pathogens in Food

1-Food itself: soil contaminated, water irrigation

Vibrio, Brucella, Salmonella

2-Food Handlers :Cooks, workers, waiters .

Staph, Salmonella, Shigella, hepatitis

3 -Environment:Food storage, sanitation of markets, utensils and benches,food

transport Bacillus, Yersinia, Campylobacter

Food risky to food-borne dz .

• Fermented/ pickled food• sausages, pickled vegetables, yoghurt

• 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 poisoning

• Look for pathogenic organisms in food, patient samples,etc.

• Look for toxins in food• Must take samples from 1- Patients 2-Handlers 3- Food Leftovers 4- Utensils and 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 hybridisation– 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

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 35c 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 mediaIncubate at 35oC, for24 h.Colony count

Analysis of food using ATP photometry

• Breakdown non microbial cells in food ( somatic cells)to release their ATP

• Remove the non microbial ATP using the enzyme ATPase

• Release the bacterial ATP from bacterial cells• Assay the amount of bacterial ATP by the addition of

firefly luciferin/ luciferase• Record the amount of light emitted using ATP

photometer• Using a correlation curve to convert relative light

units to colony forming units (cfu's)/ml

Rapid tests

• Commercial kits: many• Faster than conventional method

– e.g. the MMO-MUG method for Coliform testing

Negative Positive Negative Positive

Total Coliform E. coli

Pathogens of Most Concern on Fresh Produce

• Salmonella Shigella• Escherichia coli Campylobacter• Yersinia enterocolitica Staphylococcus aureus• Clostridium species Bacillus cereus• Vibrio species • Viruses (Hepatitis A, Norwalk)• Parasites/Protozoa- (Giardia, Entamoeba,

Toxoplasma, Sarccystis, Isopora, Cryptosporidium, Eimeria, Cyclospora)

General Control of food borne disease

• 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

• Wash hands before preparing food• 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 keys to Safer food1. 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 preparation-protect

kitchen from insects , pets2. Separate raw and cooked food- Separate 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

foods3. 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

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 method 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.